Tag Archives: cerebral cortex

Understanding Thought – Part 2, The Neuroscience of Thought

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What is thought?

We’re all familiar with thought, to be sure, just like we’re familiar with our own bodies. But just because we know our own bodies doesn’t make us all doctors. In the same way, we might know our own thoughts well, but that doesn’t make us experts in the science of thought.

But understanding thought is important. If we don’t know what thoughts are, then it’s very easy to be conned into believing the myriad of myths about thought perpetuated about them by every pop-psychologist and B-grade life coach. This series of blogs is taken from my book Hold That Thought: Reappraising the work of Dr Caroline Leaf.

We’ve looked at some basic neurobiology, and today we’ll look at the neurobiology of thought itself. Later we’ll discuss some psychological models of our thought processing, and finally we’ll discuss the common brain states and functions that are usually confused with thought.

Neuroscience of thought

Global Workspace / Intelligent Distribution Agent Model

Building on Baddeley’s model of working memory, Baars proposed the Global Workspace theory [1], and Baars and Franklin went further by adding the Intelligent Distribution Agent model [2]. Central to this model is the “Cognitive cycle”, a nine-step description of the underlying process from perception through to action. In the model, implicit neural information processing is considered to be a continuing stream of cognitive cycles, overlapping so they act in parallel. The conscious broadcast of our thought stream is limited to a single cognitive cycle at any given instant, so while these thought cycles run in in parallel, our awareness of them is in the serial, sometimes disparate, streams of words or pictures in our minds. Baars and Franklin suggests that as many as ten cycles could be running per second [3], and since working-memory tasks occur on the order of seconds, several cognitive cycles may be needed for any given working memory task, especially if it has conscious components such as mental rehearsal [2].

In recent years, the Global Workspace/Intelligent Distribution Agent hypothesis has been updated to help facilitate the quest to create different forms of artificial intelligence. The LIDA (“Learning Intelligent Distribution Agent”) model incorporates the Global Workspace theory with the concepts of memory formation to create a single, broad, systems-level model of the mind.

Franklin et al summarise the process, “During each cognitive cycle the LIDA agent first makes sense of its current situation as best as it can by updating its representation of its current situation, both external and internal. By a competitive process, as specified by Global Workspace Theory, it then decides what portion of the represented situation is the most salient, the most in need of attention. Broadcasting this portion, the current contents of consciousness, enables the agent to chose an appropriate action and execute it, completing the cycle.” [4] Information within the cognitive cycle is broadcast to our consciousness in order to recruit a wider area of the brain to enhance the processing of that information [2, 5]. It’s the broadcasting of this portion of the information flow that renders it “conscious”.

Thought, therefore, is simply a broadcast of one part of a deeper flow of information. This is very important, as it means that thought is not an instigator or a controlling force. It’s not a case of, “I think, therefore, I am”, but, “I am, therefore, I think.”

Neural networks involved in the neurobiology of thought?

There is good evidence that working memory, and the attention required to select the information streams that fill the global workspace at any one moment, are intrinsically linked to a group of brain regions tagged as the Prefrontal Parietal Network [6]. Disease or damage to the PPN or impairment of the PPN in the lab impairs normal conscious function. Research-level brain imaging studies have strongly implicated the PPN in perceptual transitions, the conscious detection of stimuli in a range of modalities, sustaining percepts, and in metacognitive decisions (awareness of awareness) on those percepts. Finally, a reduction of conscious level when under general anesthesia is associated with a reduced lateral prefrontal activity [6].

Other neural networks have been defined that are also important in the neurophysiology of conscious awareness. When there are no external stimuli, the brain doesn’t just turn off. Some parts of the brain become even more active. The same parts of the brain are active when we daydream (what researchers call “stimulus independent thought”).

We have all experienced this at some point. Our body will be doing something while our brain is off somewhere else. I find this happens to me when I’m driving home from work. Going the same route every day means that I often drift into autopilot as I’m thinking about the events of the day or my stomach reminds me that I’m hungry, and five minutes later I pay attention to my surroundings and realise that I’m nearly home.

There are many other sentinel neurocognitive networks, among them: the default mode network, the central executive network, and the salience network. The central executive network is involved in actively working on an external task, which we think of as attention. The default mode network is involved in autobiographical retrieval and self-monitoring activity, the “stimulus independent thought”, or day-dreaming. The salience network acts as a switch between the two, figuring out which external stimuli need active attention and switching on the central executive network [7]. Whichever one of these networks is active at the time, that network is actively feeding information into the working memory, which is what we perceive as “thought”.

When the brain is engaged in a new or difficult task requiring active attention, the executive parts of the brain overtake the default mode network. But when attention is not actively required such as well-practiced tasks, or if our attention diminishes as with boring tasks, the Default Mode Network becomes dominant again. The switch between attention and the default mode network is strongly related to the neurotransmitter dopamine [8]. These networks heavily overlap with the Prefrontal Parietal Network and the global workspace model.

Recent neurobiological evidence confirms the role the default mode network in thought processing, specifically the part of the brain called the cingulate cortex.   This has been confirmed in studies in healthy subjects [9], and in people with formal thought disorders (especially auditory verbal hallucinations) [10]. Specifically, the DMN is often the part of the brain that is the most active in remembering the past, and using similar mechanisms, also the simulations of the future. It is linked to daydreaming and creativity especially when a problem is allowed to “incubate” for a while, while the brain is involved in another task that is more menial, or low stress. It’s theorised that the attentional and implicit networks in the brain are brought into a closer proximity and allowed to interact, which improved the likelihood that a novel solution would be discovered [11].

Research into the topics of thought and consciousness is ever-growing and expanding, and if you want to read more about these topic, they have been very well covered in a two part series from De Sousa, [12] and [13].

References

  1. Baars, B.J., A cognitive theory of consciousness. 1988, Cambridge University Press, Cambridge England ; New York:
  2. Baars, B.J. and Franklin, S., How conscious experience and working memory interact. Trends Cogn Sci, 2003. 7(4): 166-72 http://www.ncbi.nlm.nih.gov/pubmed/12691765 ; http://bit.ly/1a3ytQT
  3. Madl, T., et al., The timing of the cognitive cycle. PLoS One, 2011. 6(4): e14803 doi: 10.1371/journal.pone.0014803
  4. Franklin, S., et al., Conceptual Commitments of the LIDA Model of Cognition. Journal of Artificial General Intelligence, 2013. 4(2): 1-22
  5. Baars, B.J., Global workspace theory of consciousness: toward a cognitive neuroscience of human experience. Progress in brain research, 2005. 150: 45-53
  6. Bor, D. and Seth, A.K., Consciousness and the prefrontal parietal network: insights from attention, working memory, and chunking. Front Psychol, 2012. 3: 63 doi: 10.3389/fpsyg.2012.00063
  7. Meehan, T.P. and Bressler, S.L., Neurocognitive networks: findings, models, and theory. Neurosci Biobehav Rev, 2012. 36(10): 2232-47 doi: 10.1016/j.neubiorev.2012.08.002
  8. de Wit, S., et al., Reliance on habits at the expense of goal-directed control following dopamine precursor depletion. Psychopharmacology (Berl), 2012. 219(2): 621-31 doi: 10.1007/s00213-011-2563-2
  9. Shackman, A.J., et al., The integration of negative affect, pain and cognitive control in the cingulate cortex. Nat Rev Neurosci, 2011. 12(3): 154-67 doi: 10.1038/nrn2994
  10. Lutterveld, R.v., et al., Network analysis of auditory hallucinations in nonpsychotic individuals, in Auditory verbal hallucinations and the brain, Lutterveld, R.v., (Ed). 2013, University Medical Center Utrecht: The Netherlands. p. 117-37.
  11. Baird, B., et al., Inspired by distraction: mind wandering facilitates creative incubation. Psychol Sci, 2012. 23(10): 1117-22 doi: 10.1177/0956797612446024
  12. De Sousa, A., Towards an integrative theory of consciousness: part 1 (neurobiological and cognitive models). Mens Sana Monogr, 2013. 11(1): 100-50 doi: 10.4103/0973-1229.109335
  13. De Sousa, A., Towards an integrative theory of consciousness: part 2 (an anthology of various other models). Mens Sana Monogr, 2013. 11(1): 151-209 doi: 10.4103/0973-1229.109341

Understanding Thought – Part 1

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WHAT IS THOUGHT?

We’re all familiar with thought, to be sure, just like we’re familiar with our own bodies. But just because we know our own bodies doesn’t make us all doctors. In the same way, we might know our own thoughts well, but that doesn’t make us experts in the science of thought.

But understanding thought is important. If we don’t know what thoughts are, then it’s very easy to be conned into believing the myriad of myths about thought perpetuated about them by every pop-psychologist and B-grade life coach.

This series of blogs is taken from my book Hold That Thought: Reappraising the work of Dr Caroline Leaf. We will look at some basic neurobiology first, then look at the neurobiology of thought itself. We’ll discuss some psychological models of our thought processing, and finally we’ll discuss the common brain states and functions that are usually confused with thought.

Neurobiology 101

The nerve cell

At the most fundamental level of our thought process is the nerve cell, also called a neuron. Nerve cells, like all cells in the body, have a nucleus containing the genetic material. The nucleus is surrounded by cytoplasm, a watery chemical soup that contains the functional proteins that make the cell run. A thin lipid layer called the cell membrane envelopes the nucleus and cytoplasm. The cell membrane contains important protein structures such as receptors that help the cell receive signals from other cells, and ion channels, which help the cell regulate its internal chemistry.

Compared to other cells, nerve cells have three unique structures that help them do their job. First are dendrites, which are spiny branches that protrude from the main cell body, which receive the signals from other nerve cells. Leading away from the cell body is a long thin tube called an axon which helps carry electrical signal from the dendrites, down to the some tentacle-like processes that end in little pods. These pods, called the terminal buttons of the axon, and then convey the electrical signal to another nerve cell by directing a burst of chemicals towards the dendrites of the next nerve cell in the chain.

In order for the signal to be successfully passed from the first nerve cell to the second, it must successfully traverse a small space called the synapse.

The synapse

Despite being very close to each other, no nerve cell touches another. Instead, the spray of chemicals that’s released from the terminal button of the axon floats across a space of about 20-40nM (a nanometre is one billionth of a metre).

There are a number of different chemicals that traverse synapses, but each terminal button has its own particular one. The most well known are serotonin, noradrenaline and dopamine.

If the signal from the first nerve is strong enough, then a critical amount of the chemical is released and will make it across the gap to the dendrites of the second nerve cell on the other side. The chemical interacts with specific receptors on the new dendrites, which cause them to open up to certain salts like sodium and potassium. As sodium and potassium move in and out of the cell, a new electrical current if formed in the second nerve cell, passing the signal down the line.

To prevent the chemicals in the synapse from over-stimulating the second nerve cell, enzymes breakdown the chemicals to clear the space before the next signal comes past.

Nerve pathways

Combining nerve cells and synapses together creates a nerve pathway, where the input signal is received by specialised nerve endings and is transmitted down the nerve cell across a synapse to the next nerve cell, across the next synapse to the next nerve cell, and on and on until the signal has reached the destination for the output of that signal.

And that’s it. The entire nervous system is just a combination of nerve cells and the synapses between them.

What gives the nervous system and brain the near-infinite flexibility, and air of mystery, is that there are eighty-six billion nerve cells in the average adult (male) brain. Each nerve cell has hundreds to thousands of synapses. It’s estimated that there are about 0.15 quadrillion (that’s 150,000,000,000,000) synapses throughout the average brain [1]. And that’s not including the nerve cells and synapses in the spinal cord, autonomic nervous system and throughout the body. Each of these cells and synapses connect in multiple directions and levels, and transmit signals through the sum of the exciting or inhibiting influences they receive from, and pass on to, other nerve cells.

Single nerve cells may have the appearances of trees with their axon trunks and dendritic branches. But altogether, the billions of connections would more resemble a box of cobwebs.

Higher order brain structures

But unlike a box of cobwebs, the brain has precise organisation to the myriad of connections. These areas can be defined either by their structure, or by their function.

Structurally, there are areas in the brain that are dominated by nerve cell bodies, formed into a little cluster, called a nucleus (different from the nucleus of each cell). Then there are groups of axons bundled together, called a tract, which behave like a data cable for your computer. Nuclei process multiple sources of signal and refine them. The refined signals are sent into the appropriate tract to be transmitted to either another set of nuclei for further refinement, or to distant structures to carry out their effect. The axons of the nerve cells that make up the tracts are usually covered in a thick white material called myelin. Myelin acts like insulation on a wire, improving the speed and accuracy of the communicated signal. Parts of the brains with lots of myelinated cells are described as “white matter”. The nuclei and the cerebral cortex (the outer covering of the brain) are unmyelinated cells, and are referred to as “grey matter”.

On a functional level, the brain is divided into parts depending on what information is processed, and how it gets processed. For example, the cerebral cortex is divided into primary areas for the senses and for motor functions, secondary areas and tertiary association areas. The primary sensory areas detect specific sensations, whereas the secondary areas make sense out of the signals in the primary areas. Association areas receive and analyze signals simultaneously from multiple regions of both the motor and sensory areas, as well as from the deeper parts of the brain [2]. The frontal lobe, and specifically pre-frontal cortex, is responsible for higher brain functions such as working memory, planning, decision making, executive attention and inhibitory control [3].

Everything our senses detect is essentially deconstructed, processed then reconstructed by our brains. For example, when reading this page, the image is decoded by our retina and sent through a number of pathways to finally reach the primary visual cortex at the back of our brain. The primary visual cortex has 6 layers of nerve cells which simultaneously encode the various aspects of the image (especially colour, intensity and movement of the signals) and this information is sent to the secondary association areas that detect patterns, both basic (lines are straight, curved, angled) and complex (two diagonal intersecting lines form an ‘x’). One part of the secondary association areas in the visual cortex (the Angular Gyrus) processes these patterns further into the patterns of written words. The information on the various patterns that were discerned by the secondary association areas then get sent to the tertiary association area for the senses where those visual patterns are combined with patterns processed from other sensory areas (hearing, touch and internal body sensations) to form a complex pattern of multimodal association [2]. In the case of reading, the tertiary association area allows comprehension of the written words that were previously only recognised as words by the secondary association areas.

In the recent decades, with the widespread adoption of non-invasive methods of studying the active living brain such as PET scanning and fMRI, researchers have discovered that rather than discrete parts of the brain lighting up with a specific task, entire networks involving multiple brain regions are activated. This has lead to the paradigm of neurocognitive networks, in which the brain is made up of multiple interconnected networks that “are dynamic entities that exist and evolve on multiple temporal as well as spatial scales” and “by virtue of both their anatomical and functional architectures, as well as the dynamics manifested through these architectures, large-scale network function underlies all cognitive ability.” [4]

Emotions and feelings

Emotions are a difficult concept to define. Despite being studied as a concept for more than a century, the definition of what constitutes an emotion remains elusive. Some academics and researchers believe that the term is so ambiguous that it’s useless to science and should be discarded [5].

I’ll discuss emotions further in chapter 2, but for now, it’s easiest to think of our emotional state as the sum total of our different physiological systems, and feelings are the awareness, or the perception of our emotional state.

Different parts of the brain are responsible for the awareness of these feelings. The amygdala is often considered the seat of our fears, the anterior insula is responsible for the feeling of disgust, and the orbitofrontal and anterior cingulate cortex are involved in a broad range of different emotions [6].

Different emotional states are linked with different neurotransmitters within the brain. For example, a predisposition to anxiety is often linked to variations in the genes for serotonin transport [7] while positive and negative affect (“joy / sadness”) are linked to the dopaminergic system [8].

Memories

Memories, like thoughts, are something that we’re all familiar with in our own way.

Memory is quite complicated. For a start, there’s more than one form of memory. You’ve probably heard of short term and long term memory. Short term memory is further thought of as sensory memory and working memory. Long term memory is divided into semantic and episodic memory. Memory is also classified as either declarative memory, also called explicit memory, and nondeclarative memory, also called implicit memory.

Squire and Wixted explain, “Nondeclarative memory is neither true nor false. It is dispositional and is expressed through performance rather than recollection. These forms of memory provide for myriad unconscious ways of responding to the world. In no small part, by virtue of the unconscious status of the nondeclarative forms of memory, they create some of the mystery of human experience. Here arise the dispositions, habits, and preferences that are inaccessible to conscious recollection but that nevertheless are shaped by past events, influence our behavior and mental life, and are an important part of who we are.” [9]

On the other hand, declarative memory “is the kind of memory that is referred to when the term memory is used in everyday language. Declarative memory allows remembered material to be compared and contrasted. The stored representations are flexible, accessible to awareness, and can guide performance in a variety of contexts. Declarative memory is representational. It provides a way of modeling the external world, and it is either true or false.” [9]

Working memory is a central part of the memory model. Information from feelings, stored memories and actions all converge in working memory. The model of working memory initially proposed by Baddeley involves a central executive, “a control system of limited attentional capacity that is responsible for the manipulation of information within working memory and for controlling two subsidiary storage systems: a phonological loop and a visuospatial sketchpad.”[10] Baddeley later added a third subsidiary system, the episodic buffer, “a limited capacity store that is capable of multi-dimensional coding, and that allows the binding of information to create integrated episodes.” [10]

Working memory is known to be distinct from other longer term memories that are dependent on part of the brain called the hippocampus, because patients with severe damage to the hippocampus can remember a small amount of information for a short time, but are not able to push that information into longer term memory functions to retain that information. Information in working memory doesn’t last for any more than a few minutes [9].

So, there are many forms of memory that are important to our lives and influence our behaviour that are “inaccessible to conscious recollection”. But even declarative memory, which is accessible to thought, doesn’t actually make up the thought itself. Memories are stored representations.

When memories are formed or retrieved, the information is processed in chunks. As Byrne pointed out, “We like to think that memory is similar to taking a photograph and placing that photograph into a filing cabinet drawer to be withdrawn later (recalled) as the ‘memory’ exactly the way it was placed there originally (stored). But memory is more like taking a picture and tearing it up into small pieces and putting the pieces in different drawers. The memory is then recalled by reconstructing the memory from the individual fragments of the memory.” [11] Recalling the original memory is an inaccurate process, because sometimes these pieces of the memory are lost, faded or mixed up with another [12]. This is why what we perceive and what we recall are often two different things entirely.

Why do we have memory then, if it’s so flawed at recalling information? Because memory is less about recalling the past, and more about imagining and planning the future. As Schacter writes, “The constructive episodic simulation hypothesis states that a critical function of a constructive memory system is to make information available in a flexible manner for simulation of future events. Specifically, the hypothesis holds that past and future events draw on similar information and rely on similar underlying processes, and that the episodic memory system supports the construction of future events by extracting and recombining stored information into a simulation of a novel event. While this adaptive function allows past information to be used flexibly when simulating alternative future scenarios, the flexibility of memory may also result in vulnerability to imagination-induced memory errors, where imaginary events are confused with actual events.” [13]

References

  1. Sukel, K. The Synapse – A Primer. 2013 [cited 2013, 28/06/2013]; Available from: http://www.dana.org/media/detail.aspx?id=31294.
  2. Hall, J.E. and Guyton, A.C., Guyton and Hall textbook of medical physiology. 12th ed. 2011, Saunders/Elsevier, Philadelphia, Pa.:
  3. Stuss, D.T. and Knight, R.T., Principles of frontal lobe function. 2nd ed. 2013, Oxford University Press, Oxford ; New York:
  4. Meehan, T.P. and Bressler, S.L., Neurocognitive networks: findings, models, and theory. Neurosci Biobehav Rev, 2012. 36(10): 2232-47 doi: 10.1016/j.neubiorev.2012.08.002
  5. Dixon, T., “Emotion”: The History of a Keyword in Crisis. Emot Rev, 2012. 4(4): 338-44 doi: 10.1177/1754073912445814
  6. Tamietto, M. and de Gelder, B., Neural bases of the non-conscious perception of emotional signals. Nat Rev Neurosci, 2010. 11(10): 697-709 doi: 10.1038/nrn2889
  7. Caspi, A., et al., Genetic sensitivity to the environment: the case of the serotonin transporter gene and its implications for studying complex diseases and traits. Am J Psychiatry, 2010. 167(5): 509-27 doi: 10.1176/appi.ajp.2010.09101452
  8. Felten, A., et al., Genetically determined dopamine availability predicts disposition for depression. Brain Behav, 2011. 1(2): 109-18 doi: 10.1002/brb3.20
  9. Squire, L.R. and Wixted, J.T., The cognitive neuroscience of human memory since H.M. Annu Rev Neurosci, 2011. 34: 259-88 doi: 10.1146/annurev-neuro-061010-113720
  10. Repovs, G. and Baddeley, A., The multi-component model of working memory: explorations in experimental cognitive psychology. Neuroscience, 2006. 139(1): 5-21 doi: 10.1016/j.neuroscience.2005.12.061
  11. Byrne, J.H. Learning and Memory (Section 4, Chapter 7). Neuroscience Online – an electronic textbook for the neurosciences 2013 [cited 2014, Jan 3]; Available from: http://neuroscience.uth.tmc.edu/s4/chapter07.html.
  12. Bonn, G.B., Re-conceptualizing free will for the 21st century: acting independently with a limited role for consciousness. Front Psychol, 2013. 4: 920 doi: 10.3389/fpsyg.2013.00920
  13. Schacter, D.L., et al., The future of memory: remembering, imagining, and the brain. Neuron, 2012. 76(4): 677-94 doi: 10.1016/j.neuron.2012.11.001

Dr Caroline Leaf and the myth of the myth of multitasking

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Can you successfully multitask?

According to Dr Caroline Leaf, communication pathologist and self-titled cognitive neuroscientist, multi-tasking is a myth.

Actually, Dr Leaf isn’t completely wrong. Her factoid is so vague that there may be some truth in it somewhere. The problem with teaching via vague factoid is that no one can apply anything from it. If we were to take Dr Leaf’s statement as a specific teaching or advice, then we would be misled.

Why? Because it all comes down to how you define ‘multi-tasking’.

I have a couple of patients in a nursing home, two old ladies who sit on a balcony in the sun, knitting and talking at the same time. Isn’t that multi-tasking? Think of what you do every day. How often are you doing something menial while doing something requiring a bit more attention? How often do you have a conversation with your passenger while your driving? Isn’t that multi-tasking? When you get up in the morning and you are able to make a cup of tea and some breakfast at the same time, read some of the paper or your e-mails while you’re eating your breakfast at the same time, etc. Isn’t that multi-tasking?

We multi-task all the time. If we had to do everything in a linear, sequential fashion, we would never get anything done. We are able to multi-task because routine tasks have become largely habitualised by our brains and don’t need lots of processing power to complete. Hence why we can do something as complex a driving a car while still talking to our passenger or listening to music. Certain occupations, such as air-traffic control, involve high levels of multi-tasking [1].

When a task is new and/or complicated, our brains need to utilise our resources of attention to properly process the information required by the task. There is only so much that our working memory can handle. Our working memory uses tricks to handle larger amounts of information through a process called “chunking” [2] but there is still a finite limit. Performing two or more cognitively demanding tasks at the same time is difficult, and the brain can often cope by shifting tasks, although there is always a price to pay for this [3].

So it is true that there are some tasks that require more of the cognitive capacity of the brain to process. The higher the cognitive load, the more capacity needed, and the less likely that the brain will be able to multi-task with it. Thus, it’s reasonable to suggest that we can’t multi-task all of the time with every task we have to perform (although the more we do a task, the more habitual it becomes, thus reducing the cognitive load of the task, and increasing our ability to multi-task it).

However it’s misleading to say that we can’t multi-task at all. It’s a myth that multi-tasking is a myth. Dr Leaf’s comment that, “Paying attention to one task at a time is the correct way”, isn’t a summary of the neuroscience of attention, but a subjective statement based on her grandiose pretension. There is no objective evidence that “one task at a time” offers generally applicable benefit.

So don’t be afraid of multi-tasking. Just know your limits.

References

  1. Nelson, J.T., et al., Enhancing vigilance in operators with prefrontal cortex transcranial direct current stimulation (tDCS). Neuroimage, 2014. 85 Pt 3: 909-17 doi: 10.1016/j.neuroimage.2012.11.061
  2. Bor, D. and Seth, A.K., Consciousness and the prefrontal parietal network: insights from attention, working memory, and chunking. Front Psychol, 2012. 3: 63 doi: 10.3389/fpsyg.2012.00063
  3. Monsell, S., Task switching. Trends in cognitive sciences, 2003. 7(3): 134-40

Hold That Thought – Reappraising the work of Dr Caroline Leaf

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Hold That Thought Cover

It’s been more than a few late nights in the making, but sixteen months and 68,000 words on, the early release of my new book is now available on line through Smashwords: https://www.smashwords.com/books/view/466848.  Apple iBook, Kindle, and a number of other platforms will come online soon.

Dr Caroline Leaf is a South African communication pathologist and self-titled cognitive neuroscientist, now based in the USA.  This book is an in-depth look at the current scientific understanding of thought, stress, free will and choice, as well as a thorough critique of Dr Leaf’s foundational teachings and the evidence she provides as proof of her hypotheses.

In the coming few days, I will make the text of the book available on this blog as well.  If you have any questions, send them in.  I’m happy to put up a FAQ page.  And as always, I’m happy to answer any legitimate criticism of my work, so long as it’s constructive and evidence based, not personal.

And as always, Dr Leaf herself is welcome to comment.  Indeed, I would value her feedback, and I’m sure any comment she wishes to make would be welcome by the Christian community as a whole.

Dr Caroline Leaf, Dualism, and the Triune Being Hypothesis

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Executive Summary

The idea that humans have an immaterial soul, separate to the body, has spanned history and culture. This idea is known as dualism. The concept of the spirit is fundamental to the Christian church. Christians are usually taught that humans are a spirit, having a soul and living in a body (the Triune Being Hypothesis). The concept permeates the work of Dr Caroline Leaf, forming the basis for her assumptions that our minds can control matter.

However, the Bible does not state that the spirit and soul are separate to the body, only that they are linked in the earthly and supernatural realms. Over the last few decades, cognitive neuroscience has demonstrated that definable neural networks within the human brain mediate the components of the traditional soul. Religious belief and spiritual experiences are also heavily reliant on the human brain.

These findings, along with a number of other philosophical objections, prove that dualism is not compatible with science or philosophy. Dr Leaf’s reliance on the concept of dualism creates an intellectual dissonance between her teaching and neuroscience.

The notion that the soul and the spirit are separate to the body is also incorrect. However, quantum physics, and String Theory in particular, suggest that other dimensions and other universes exist, which may provide a scientifically plausible explanation of both natural and supernatural realms. It may be that our earthly body houses our natural spirit and soul within the brain, but that these are translocated to the celestial realm upon death. The challenge for the Christian church now is to unite the evidence of cognitive neuroscience with the description of the spirit, soul and body from scripture and further delineate the doctrine of humans as triune beings.

(Word count: 7256, including references)

Introduction

Are we a body with a mind, or a mind with a body?

It sounds a bit like the age-old chicken and the egg conundrum. In Ancient Greece, Plato proposed that human beings have an immaterial soul distinct from the material body while Descartes reinvigorated the idea in the 17th century. But the idea of the distinct immaterial soul is also found throughout different religions, and seems to be interwoven through the Bible as well.

For Dr Caroline Leaf, Communication Pathologist and self-titled Cognitive Neuroscientist, dualism is fundamental to her theory of “Mind over Matter”. In her 2013 book, “Switch On Your Brain”, Dr Leaf states that, “Our mind is designed to control the body, of which the brain is a part, not the other way around. Matter does not control us; we control matter through our thinking and choosing.” [1: p33] She has also made several similar public statements via her social media feeds, such as, “Don’t blame your physical brain for your decisions and actions. You control your brain!” (6/6/2014) and “Your mind is all powerful! Your brain simply captures what your mind dictates! 2 Timothy 1:7.” (11/5/2014)

I have previously blogged about the scriptural and scientific voracity of Dr Leaf’s various statements on the Mind-Body problem (see also “Dr Caroline Leaf and the Myth of the Blameless Brain“, and others). But when she published, “Your mind will adjust your body’s biology and behaviour to fit with your beliefs” (21/6/2014) I thought enough was enough. The concept of dualism not only permeates the teachings of Dr Leaf, but also significantly influences the current understanding of the Biblical principles of the soul and spirit. So, this topic deserves an in-depth review, to ensure that the thinking within the church aligns with both scripture and science.

The Triune Being Hypothesis

On the 9th of June 2014, Dr Leaf published another meme on her social media feeds, “We are triune beings designed to be lead by the Holy Spirit … who speaks to our spirit. Our spirit controls our soul/mind and our soul/mind controls our body.”

By virtue of growing up in a Christian family, going to a Christian school, and digesting thousands of sermons during my lifetime, I’m very familiar with the concept of humans as a triune being (“triune”, meaning “three in one”). The concept I’ve been taught is similar to Dr Leaf’s view: that humans consist of three separate but interlinked components, the ethereal spirit and soul, and the physical body. The soul, in turn, consists of the mind, will and emotions. The three-part design reflects the image of God who is, of course, a triune being (the Holy Trinity: Father, Son and Holy Spirit). The hypothesis proposes that the body is just an earthly dwelling for a being that is fundamentally spirit in nature, the soul being the intermediary between the two.

In keeping with the theme, this essay will be in three parts! First, I review the Biblical evidence relating to the body, soul and spirit. Second, I review the scientific evidence relating to the spirit and soul. And finally, I discuss how the scriptural and scientific evidence relates to our current understanding of dualism, the triune being hypothesis and the implications for Dr Leaf and Christianity more broadly.

The Bible on the Triune Being Hypothesis

One of the fundamental arguments used by those who support the idea of man as a triune being is the way the Apostle Paul used distinct words to describe body, soul and spirit within the same sentence. For example, in 1 Thessalonians 5:23, Paul wrote, “And the very God of peace sanctify you wholly; and I pray God your whole spirit and soul and body be preserved blameless unto the coming of our Lord Jesus Christ” (emphasis added).

The three words used in ancient Greek were pneuma (‘spirit’), psyche (‘soul’) and soma (‘body’). According to Thayer’s Greek Lexicon, the words pneuma (‘spirit’) and psyche (‘soul’) were often used indiscriminately. So although the Apostle Paul distinctly used the word pneuma separately to the word psyche as in 1 Thessalonians 5:23, most of the other New Testament writers weren’t so precise.

James wrote that without the spirit (pneuma), the body (soma) would die (James 2:26). This also suggests that the spirit is different to the body, but still integral to the whole person, although given the interchangeable use of the terms, James may have also been referring to the soul.

However, Jesus told the disciples in Matthew 10:28, “And fear not them which kill the body (soma), but are not able to kill the soul (psyche): but rather fear him which is able to destroy both soul (psyche) and body (soma) in hell.” This suggests that both the soul and the body maybe found in hell, a post-death spiritual dimension (see also Luke 12:5). So it seems that at least in some form, our supernatural selves also possess a body and mind.

This idea seems to have some backing in the form of the description given in the Bible of the resurrected body of Jesus. After Jesus was crucified and buried, scripture describes the empty tomb, and the multiple sightings of Jesus by the disciples up until the time that he ascended into heaven (Luke 24). He walked along the road to Emmaus with two disciples, Cleopas and probably Cleopas’ wife Mary (see also John 19:25). He then appeared in the middle of the group of disciples within an instant. He still possessed the defects caused by the crucifixion. He ate some broiled fish and some honeycomb (see Luke 24:42-43). He said to the disciples at this meeting with them, “Behold my hands and my feet, that it is I myself: handle me, and see; for a spirit hath not flesh and bones, as ye see me have.” (Luke 24:39) Not only did he have the same physical characteristics as his pre-resurrected body (same appearance, same gender etc), but he also had similar mental traits, such as self-awareness, memory of his pre-resurrection life, and emotions and connection to the people around him. However, he was not subject to the natural laws of physics, twice suddenly appearing in a closed room (John 20:19 and 26).

Therefore it appears that rather than being a spirit housed in a body and furnished with a soul, we are instead an inseparable combination of body, soul and spirit – three unique but indivisible parts – but in different dimensions depending on which side of eternity we currently reside.

1 Thessalonians 5:23 confirms, rather than precludes, this view. Reviewing the scripture again, Paul wrote, “And the very God of peace sanctify you wholly; and I pray God your whole spirit and soul and body be preserved blameless unto the coming of our Lord Jesus Christ.” Paul chooses to emphasize all three components of our triune being equally in his prayers and wishes. If only our spirit was to pass into the celestial realm, then Paul wouldn’t have needed to delineate the three parts of our triune composition, but could have instead written “And the very God of peace sanctify you wholly; and I pray God your whole spirit be preserved blameless unto the coming of our Lord Jesus Christ”. By penning, “whole spirit and soul and body be preserved blameless”, Paul seems to treat all three parts as equally important to our future with Christ.

It follows that if we believe that our heavenly body is an integral part with our spirit and soul on the celestial side of eternity, then it should follow that our spirit and our soul are part of, and dependent on, our earthly body on this side of eternity.

This proposal differs from the conventional wisdom at two fundamental points:

1. I suggest that the spirit is integral to, and dependent on our earthly body whilst we live on the earth,
and
2. I suggest that the whole person is translated across from the earthly realm to the celestial, rather than just the spirit.

Such suggestions are compatible with current scientific understanding. There is ample evidence of spiritual neural networks that complement the emotional and moral parts of our brain (this will be discussed further in a future section).

String Theory provides a plausible explanation of other dimensions and worlds in parallel with our own which could very easily explain a spiritual dimension. String Theory is the theory that the very fabric of the cosmos is made up of tiny vibrating loops of energy, which physicists call “strings”. These strings are almost impossibly small. Physicist Brian Greene said that, “Each of these strings is unimaginably small. In fact, if an atom were enlarged to the size of the solar system, a string would only be as large as a tree!” [2] It’s the shape and vibrational pattern of each of these strings that gives subatomic particles their properties, which in turn combine to make up everything we see in the universe, including ourselves.

In order for these strings to vibrate and move the way they are predicted to, String Theory postulates that there are actually 11 dimensions of space. In one of these dimensions, a string could become stretched out into a membrane, or a “brane” for short. I’ll let Brian Greene and colleagues explain it further.

“BRIAN GREENE: The existence of giant membranes and extra dimensions would open up a startling new possibility, that our whole universe is living on a membrane, inside a much larger, higher dimensional space. It’s almost as if we were living inside … a loaf of bread? Our universe might be like a slice of bread, just one slice, in a much larger loaf that physicists sometimes call the “bulk.” And if these ideas are right, the bulk may have other slices, other universes, that are right next to ours, in effect, “parallel” universes. Not only would our universe be nothing special, but we could have a lot of neighbours. Some of them could resemble our universe, they might have matter and planets and, who knows, maybe even beings of a sort. Others certainly would be a lot stranger. They might be ruled by completely different laws of physics. Now, all of these other universes would exist within the extra dimensions of M-theory, dimensions that are all around us. Some even say they might be right next to us, less than a millimetre away. But if that’s true, why can’t I see them or touch them?
BURT OVRUT: If you have a brane living in a higher dimensional space, and your particles, your atoms, cannot get off the brane, it’s like trying to reach out, but you can’t touch anything. It might as well be on the other end of the universe.
JOSEPH LYKKEN: It’s a very powerful idea because if it’s right it means that our whole picture of the universe is clouded by the fact that we’re trapped on just a tiny slice of the higher dimensional universe.” [3]

Although it sounds preposterous, String Theory isn’t a fantasy of a few physicists who have watched too many sci-fi shows. String Theory is mathematically proven, and accepted by the majority of scientists.

What if our physical reality was one brane, the supernatural realm was a different brane, and heaven was another? Angels could be all around us, in a different dimension of space that we cannot ordinarily perceive, but who have the ability to move into our dimension if required. When we die, it’s possible that our whole person is transformed into a different dimension – the supernatural or celestial brane. The physical body remains like a snakeskin left after the snake has shed it.

My theory is only one of many possible theories. Ultimately, they all remain scientifically unprovable. While String Theory is well accepted by physicists all over the world, and the predictions of extra dimensions and branes are mathematically robust, my hypothesis that the supernatural realm is a dimension of space on a brane is conjecture, and would be impossible to test mathematically or scientifically. The concept of extra dimensions and branes is one way of explaining the Bible’s description that our spirit, soul and body remain together, but in a different realm to the physical reality that we currently experience.

Science on the Triune Being Hypothesis

So if it’s possible that we can live as a whole person, spirit, soul and body, in a celestial dimension, what makes up our spirit, soul and body in the physical dimension?

Biological science and neuroscience have uncovered many of the previously mysterious qualities that define us as human beings, although there is still much more to be uncovered.

  1. THE BODY

The body is our physical selves – our flesh and blood, sealed by our coating of skin. The body is so ultimately universal, I don’t want to waste space justifying the case for the normal. The obvious physical separation makes each person easy to delineate, although there are rare exceptions that challenge the division of body and soul/spirit.

In May 2014, Faith and Hope Howie were born in Sydney (Australia) [4]. They were born with two separate faces and two brains which merged into one brain stem. They had one body. While they were considered to be conjoined twins, in the strictest medical sense, they had a condition called disrosopus, resulting from the over-expression of a protein involved in the formation of the cranial structures [5]. The condition is extremely rare, and most children with the condition are either stillborn, or don’t survive for more than 24 hours after birth. That Faith and Hope survived for 19 days is a miracle in itself.

Strictly speaking, Faith and Hope were one baby that developed two brains, rather than being twins who failed to adequately separate. So did they have two souls or one? I don’t propose to answer this question here, but it will be worth pondering as we review the concept of the soul.

  1. THE SOUL

The soul is traditionally considered to consist of the mind, will and emotions. In the earthly realm, there is overwhelming evidence that all the parts of the traditional soul are found in the human brain.

a. The Mind

The mind is considered to be “a person’s ability to think and reason; the intellect.” [6] As we will discuss in more detail later, dualism suggests that the mind is an ethereal force separate to the body. But modern neuroscience has accumulated decades of evidence to the contrary. Our stream of consciousness is linked to the function of our working memory [7, 8]. Working memory in turn is heavily dependent on the part of the brain called the pre-frontal cortex and on a neurotransmitter called dopamine [9]. When dopamine-secreting nerve cells are damaged in the pre-frontal cortex, conditions involving disordered thought such as schizophrenia occur [9, 10]. Schizophrenia is best known for hallucinations, essentially hearing and/or seeing things that are not there. These symptoms are reversed by medications that enhance the dopamine response [11]. Lesions of the frontal lobe can also result in the loss of abstract thinking [9]. So it is fair to say that the function of the mind is dependent on the brain, specifically the pre-frontal cortex. If the function of the pre-frontal cortex is disrupted, either by damage to a group of cells, or by impairment of the signaling of those cells via disruption of the neurotransmitter dopamine, the patterns of thought change. These changes in the patterns of thought can be reversed if the impairment can be reversed. Therefore the mind is dependent on the brain. If the mind were independent of the brain, then the function of the mind would not be affected by damage or impairment to the physical brain.

Our stream of thought is a function of our working memory utilizing a wider area of the brains cortex to better process important information. Baars [7, 12] noted that the conscious broadcast comes into working memory which then engages a wider area of the cerebral cortex necessary to most efficiently process the information signal.

We perceive thought most commonly as either pictures or sounds in our head (“the inner monologue”), which corresponds to the slave systems of working memory. When you “see” an image in your mind, that’s the visuospatial sketchpad. When you listen to your inner monologue, that’s your phonological loop. When a song gets stuck in your head, that’s your phonological loop as well, but on repeat mode.

There is another slave system that Baddeley included in his model of working memory called the episodic buffer, “which binds together complex information from multiple sources and modalities. Together with the ability to create and manipulate novel representations, it creates a mental modeling space that enables the consideration of possible outcomes, hence providing the basis for planning future action.” [13]

Deep thinking is a projection from your brains executive systems (attention or the default mode network) to the central executive of working memory, which then recalls the relevant information from long-term memory and directs the information through the various parts of the slave systems of working memory to process the complex details involved. For example, visualizing a complex scene of a mountain stream in your mind would involve the executive brain directing the central executive of working memory to recall information about mountains and streams and associated details, and project them into the visuospatial sketchpad and phonological loop and combine them via the episodic buffer. The episodic buffer could also manipulate the scene if required to create plans, or think about the scene in new or unexpected ways (like imagining an elephant riding a bicycle along the riverbank).

Even though the scene appears as one continuous episode, it is actually broken up into multiple cognitive cycles, in the same way that images in a movie appear to be moving, but are really just multiple still frames played in sequence.

So our mind, also called our stream of thought, is simply a projection of information from our working memory, broadcast to our cerebral cortex, and our consciousness, for extra processing power. It is dependent on our pre-frontal cortex. When the pre-frontal cortex is damaged, our mind can experience defective output, as is the case in thought disorders such as schizophrenia.

b. The Will

The second part of our soul is our will, “the faculty by which a person decides on and initiates action.” [6] Like our mind, the feeling that we have free will is a ubiquitous human trait. Haggard observed, “Most adult humans have a strong feeling of voluntary control over their actions, and of acting ‘as they choose’. The capacity for voluntary action is so fundamental to our existence that social constraints on it, such as imprisonment and prohibition of certain actions, are carefully justified and heavily regulated.” [14]

Again, like the mind, our feeling of our will comes from our brain. Over three decades ago, Libet performed an experiment that demonstrated measurable neural activity occurring up to a full second before a test subject was consciously aware of the intention to act [15]. More recently, a study by Soon et al showed that predictable brain activity occurred up to eight seconds before a person was aware of their intention to act [16].  Haggard again, “Modern neuroscience rejects the traditional dualist view of volition as a causal chain from the conscious mind or ‘soul’ to the brain and body. Rather, volition involves brain networks making a series of complex, open decisions between alternative actions.” [14]

These brain networks initially involve the basal ganglia deep in the brain along with the dopamine rewards system, which provide a flexible interaction between the person’s current situation and the memory of previous similar situations. Also important are the frontal lobes in general, and the pre-Supplementary Motor Area (pre-SMA) in particular, which have crucial roles in keeping actions focused and ‘on task’, or in “binding intention and action”. Parts of the pre-SMA are also active in voluntary selection between alternative tasks and in switching between the selections. An area of the anterior frontomedian cortex, near the pre-SMA, was activated in veto trials more than in trials on which participants made an action. This brain activity might have a key role in self-control [14].

Damage to different areas of the frontal cortex and the other parts of the motor system can result in a number of different conditions, highlighting the role of the brain in our “voluntary” actions. For example, blockage of a small artery in the brain called the artery of Huebner may cause a stroke of the head of the Caudate Nucleus, resulting in the loss of voluntary movement, loss of motivation and loss of speech [17]. Psychosis and ADHD are also disorders of action output of the brain, both of which improve with medications that improve the function of the frontal lobes of the brain. In children with ADHD, the change can be dramatic in a short space of time, and research across the last few decades proves the effect is more than placebo [18, 19].

The feelings of intention and the sense of agency (planning to do or being about to do something, and the sense that one’s action has indeed caused a particular external event) are so fundamental to human experience that it’s hard to consider the alternative: that our ‘free will’ is by-and-large an illusion. Our brain has already reviewed a number of alternative actions for any particular situation, and by the time that our consciousness becomes aware of the decision our brain has made, our motor area of our brain has already primed the neuromuscular circuit in preparation to perform the action. At best, our ‘free will’ is more like a veto function rather than a full conscious control of our behaviour [20]. Multiple parts of our brain are involved in the planning and execution of our actions, especially the basal ganglia and the pre-SMA.

c. The Emotions

Emotions are a difficult concept to define. Despite being studied as a concept for more than a century, the definition of what constitutes an emotion remains elusive. Some academics and researchers believe that the term is so ambiguous that it’s useless to science and should be discarded [21]. I use a concept of emotions described by Dr Alan Watkins [22], which thinks of our emotional state as the sum total of the state of our different physiological systems, while feelings are the awareness, or the perception of our emotional state. However, I should stress that this is only one concept. Often the terms “emotion” and “feelings” are used interchangeably.

That said, neurobiology has still mapped specific feelings/emotions to different parts of the brain. The amygdala is often considered the seat of our fears, the anterior insula is responsible for the feeling of disgust, and the orbitofrontal and anterior cingulate cortex are involved in a broad range of different emotions [23].

Different moods have been linked to specific neurotransmitter systems in the physical brain. A predisposition to anxiety is often linked to variations in the genes for serotonin transport [24] while positive and negative affect (“joy / sadness”) are linked to the dopaminergic system [25].

What is clear is that scientifically speaking, our emotions and the perception of them is dependent on our physical brain.

Summarizing the Soul

Dualism’s view that the soul is an ethereal force separate to the body is redundant. The evidence from the scientific study of the brain makes it clear that every aspect of the traditional ‘soul’ – the mind, will and emotions – is housed in the brain.

3. THE SPIRIT

The scientific study of spirituality is on the leading edge of scientific progress.

Whether a spiritual realm exists is not something that can be tested scientifically. I’ve discussed the Biblical view of the triune being hypothesis earlier in this essay, and suggested that a spiritual realm is at least scientifically plausible depending on your interpretation of String Theory. Ultimately, it remains a matter of faith.

The existence of the spiritual realm may be debatable, but what’s well accepted is that human beings are fundamentally spiritual. Spiritual or mystical experiences are reported across all cultures [26], and throughout history, religions in various forms have spanned the globe, integral to civilizations and the forming of cultural identity. It’s therefore not surprising to find that the brain is a focal point for spiritual experience. Just as hunger, laughter, anger and many other characteristic human traits have their own unique pathways in the brain, so does the experience of the divine.

Spirituality can be defined as “an individual’s experience of and relationship with a fundamental, nonmaterial aspect of the universe that may be referred to in many ways – God, Higher Power, the Force, Mystery and the Transcendent and forms the way by which an individual finds meaning and relates to life, the universe and everything.” [27] On consideration, spirituality encompasses both episodic mystical experiences and ongoing religious beliefs.

Spiritual experiences involve multiple brain regions, and are mediated by a number of different neurotransmitters. In a study of Carmelite Nuns reliving a spiritual experience, Beauregard and Paquette observed activation of the right medial orbitofrontal cortex, the right medial prefrontal cortex, the right dorsal anterior cingulate cortex, the right middle temporal cortex and the left superior and inferior parietal lobes [26]. There is also evidence that dopamine and serotonin are important neurotransmitters in the religious experience [27]. More recent work on the function and connectivity of the medial orbitofrontal cortex shows all of these brain regions have strong connections to each other [28], and that together they function to encode and determine the predicted and real values of our choices. In particular, the medial orbitofrontal cortex helps to encode the anticipated rewards of incoming stimuli. The anticipated and actual values for the perceived stimuli are compared to give a prediction error, which serves as a teaching signal that can be used to improve future value assignments at the time of decision-making [29]. This is intrinsically linked to the limbic rewards system via dopamine, which partially explains the increase in dopamine during intense religious experiences.

Yet spiritual experiences are more than the rewards processing of incoming stimuli. Intense religious experiences have been reported during the aura of temporal lobe epilepsy, especially on the right side [27, 30]. It maybe that the right temporal lobe is largely responsible for the sensed presence of a higher being, and for the more intense religious experiences. Some scientists even went so far as to claim that complex weak magnetic stimulation of the right temporal cortex produced intense religious experiences [31], although this maybe more related to the suggestibility of the subjects rather than the temporal lobe “stimulation” [32]. Therefore, while it is likely that the right temporal lobe is involved in experiences of spirituality, there is no lab-based repeatable evidence to confirm or delineate it.

However, the cognitive and neuroanatomical correlates of religious belief have been delineated. Kapogiannis and colleagues summarized their work by stating that, “religious belief engages well-known brain networks performing abstract semantic processing, imagery, and intent-related and emotional theory of mind, processes known to occur at both implicit and explicit levels. Moreover, the process of adopting religious beliefs depends on cognitive-emotional interactions within the anterior insulae, particularly among religious subjects. The findings support the view that religiosity is integrated in cognitive processes and brain networks used in social cognition, rather than being sui generis.” [33]

If spirituality is indeed solely based on the structure and function of the human brain, what are the implications for organized religion?

To start with, it would mean that those with deficits in certain cognitive functions would experience spirituality to a lesser degree, or at least experience it to a different degree. In keeping with this hypothesis, Canadian researchers have shown that those people with mentalization deficits (reduction in the ability to understand the mental state of oneself and others which underlies overt behaviour), such as people on the Autism spectrum, are less likely to believe in a personal God [34]. On the flipside, other people would be naturally wired to the divine: intuitive and sensitive to the experience of the spiritual.

Moreover, even if a person is not naturally spiritual, one can train oneself to become more spiritual. The brain increases the neural connections within regions that are recurrently stimulated, which leads to expertise. For example, the mid-posterior hippocampus of London taxi drivers is much larger compared to London bus drivers. London taxi drivers are required to drive anywhere in London without maps, and so develop a much larger region of spatial knowledge than the bus drivers, who drive pre-determined routes [35]. Similarly, novices who meditate show increased growth of neural networks involved in the regulation of emotion [36]. It would follow that brain regions involved in the processing of spiritual experience would increase with regular spiritual practice, resulting in a greater sense of the presence of God and his joy.

On the other hand, if acceptance of God is dependent on the function of certain networks within our brain, then how does that affect the foundational principle of salvation? Is it justice if one is condemned to eternal damnation when one has less capacity to believe in the first place?

I cannot offer a definitive answer to that question. Maybe there is no definitive answer? Given that Jesus told Nicodemus, “For God sent not his Son into the world to condemn the world; but that the world through him might be saved” (John 3:17), and that Peter says about God, “The Lord is not slow in keeping his promise, as some understand slowness. Instead he is patient with you, not wanting anyone to perish, but everyone to come to repentance” (2 Peter 3:9), I trust that God will judge everyone fairly, but I’m not sure how the capacity of a person to accept salvation is judged. Perhaps that’s something that someone who’s theologically trained can comment on.

The Triune Being Hypothesis – A New Approach

In summary, while the Bible makes a distinction between body, soul and spirit, it maintains that they are inseparable parts of the same whole person. In the earthly realm, our spirit and the various aspects that traditionally constitute our soul are all enabled though various networks within our physical brain. The Bible also offers evidence that in the transition from the terrestrial to the celestial dimensions, the whole person is translocated and transformed, not just the spirit or soul. Like a reptile shedding its skin, our earthly body and brain remain after death but the person has been translocated into the celestial realm.

Dualism

Psychoneural or Cartesian dualism is the premise that matter and mind are distinct entities or substances; that the one can exist without the other; and that they may interact, but that neither can help explain the other.

Dualism appears self-evident. It seems to explain behavior; and it accounts for the survival of the soul after death. Our mind and our body also appear separate. We have direct knowledge of our mental states, but we do not have direct knowledge of our brain states, so by simple logic, our mental states are not identical with our brain states. Dualism seems to be the obvious model of choice.

Despite claiming to be a cognitive neuroscientist, Dr Leaf embraces dualism, expanding the original concept of a soul into the broader idea of the soul and spirit of the triune being hypothesis, complete with its own hierarchy, “We are triune beings designed to be lead by the Holy Spirit … who speaks to our spirit. Our spirit controls our soul/mind and our soul/mind controls our body.” (Dr Leaf social media post, 9/6/2014)

However, we know that executive functions, emotions and even spiritual experiences can be induced or improved by stimulating the responsible brain networks (electrically in the lab, or with medications). And pathological changes to the brain, such as tumours, strokes, or brain injuries, all have the capacity to change the emotional or cognitive function of the sufferer, depending on the location of the lesion within the brain. If the mind were truly separate to the brain, then changes to the physical brain would not influence the mind or soul. Therefore, medicine and cognitive neuroscience have shown that dualism is false.

Philosophically, dualism is also fatally flawed. According to Bunge [37], dualism fails on a number of counts:

1. Dualism is conceptually fuzzy: “the expression ‘mind-body interaction’ is an oxymoron because, by hypothesis, the immaterial mind is impregnable to physical stimuli, just as matter cannot be directly affected by thoughts or emotions. The very concept of an action is well defined only with reference to material things.”
2. Dualism is experimentally irrefutable: “since one cannot manipulate a nonmaterial thing, as the soul or mind is assumed to be, with material implements, such as lancets and pills.”
3. Dualism considers only the adult mind: “Hence it is inconsistent with developmental psychology, which shows how cognitive, emotional and social abilities develop (grow and decay) along with the brain and the individual’s social context.”
4. Dualism is inconsistent with cognitive ethology: “in particular primatology … comparative psychology and cognitive archaeology”.
5. Dualism violates physics: “in particular the law of conservation of energy. For instance, energy would be created if a decision to take a walk were an event in the nonmaterial soul. Moreover, dualism is inconsistent with the naturalistic ontology that underpins all of the factual sciences.”
6. Dualism confuses even investigators who are contributing to its demise: “in the cognitive, affective and social neuroscience literature one often reads sentences of the forms ‘N is the neural substratum (or correlate) of mental function M,’ and ‘Organ O subserves (or mediates, or instantiates) mental function M’ – as if functions were accidentally attached to organs, or were even prior to them, and organs were means in the service of functions … Why not say simply that the brain feels, emotes, cognizes, intends, plans, wills, and so on? Talk of substratum, correlate, subservience and mediation is just a relic of dualism, and it fosters the idea (functionalism) that what matters is function, which can be studied independently of stuff. But there is neither walking without legs nor breathing without lungs. In general, there is neither function without organ nor organ without functions.”
7. Dualism isolates psychology from most other disciplines: “insofar as none of them admits the stuff/function dichotomy.”
8. Dualism is barren at best, and counterproductive at worst, “In fact, it has spawn superstitions and pseudosciences galore … (and) has slowed down the progress of all the disciplines dealing with the mind.”

Bunge sums up the concept of dualism, “In short, psychoneural dualism is scientifically and philosophically untenable. Worse, it continues to be a major obstacle to the scientific investigation of the mind, as well as to the medical treatment of mental disorders.”

In short, dualism is dead.

Dualism and Dr Leaf

This damning evaluation of dualism poses significant ongoing problems for Dr Leaf and her teaching. Her proposition that “Our spirit controls our soul/mind and our soul/mind controls our body” is not supported by either science or by scripture. This significantly weakens her standing as a biblical and scientific authority, and highlights an intellectual dissonance between science, scripture, and her published work.

Unless Dr Leaf is prepared to review her position and change her teaching on the subject, the gap between her teaching and the accepted scientific position will only continue to widen, and her authority and respect will continue to weaken.

The New Triune Being Hypothesis and the Christian Church

For the Christian church, the Triune Being Hypothesis in its current form is now redundant. The review of the biblical evidence, and the current evidence from neuroscience, has disproven the triune being hypothesis insofar as there is no Biblical or scientific proof that the spirit, soul and body are separate entities. However, it’s reasonable to consider the spirit, soul and body as inseparable parts of the whole being, which are translocated together into the celestial realm upon death.

At the very least, the position of the Christian church on the nature of the soul/spirit requires review, and topic should be brought back to the table to be appropriately debated. It’s clear that the old, generally accepted hypothesis of the separate, immaterial soul/spirit is untenable with current scientific evidence. In this essay, I have proposed one theory which is at least plausible with current scientific understanding. However, there are many other theories that may be just as valid, and warrant consideration.

It’s my hope that with academic honesty and divine guidance, the truth of our triune nature can be further delineated.

References

  1. Leaf, C.M., Switch On Your Brain : The Key to Peak Happiness, Thinking, and Health. 2013, Baker Books, Grand Rapids, Michigan:
  2. Greene, B. The Elegant Universe: Part 2. [Transcript] 2003 [cited 2013, November 4]; Available from: http://www.pbs.org/wgbh/nova/physics/elegant-universe.html – elegant-universe-string.
  3. Greene, B. The Elegant Universe: Part 3. [Transcript] 2003 [cited 2014, June 28]; Available from: http://www.pbs.org/wgbh/nova/physics/elegant-universe.html – elegant-universe-dimensions.
  4. Lyons, K. and Mills, D., ‘Gone to play with the angels’: Conjoined twins Faith and Hope are laid to rest after family’s tearful memorial service in Sydney. Daily Mail, UK, 2014 June 2 http://www.dailymail.co.uk/news/article-2645824/Gone-play-angels-Faith-trying-attention-Hope-happy-just-hold-finger-rest-Family-conjoined-twins-pay-tearful-tributes-Sydney-memorial-service.html
  5. Zaghloul, N.A. and Brugmann, S.A., The emerging face of primary cilia. Genesis, 2011. 49(4): 231-46 doi: 10.1002/dvg.20728
  6. Oxford Dictionary of English – 3rd Edition, 2010, Oxford University Press: Oxford, UK.
  7. Baars, B.J. and Franklin, S., How conscious experience and working memory interact. Trends Cogn Sci, 2003. 7(4): 166-72 http://www.ncbi.nlm.nih.gov/pubmed/12691765 ; http://bit.ly/1a3ytQT
  8. Franklin, S., et al., Conceptual Commitments of the LIDA Model of Cognition. Journal of Artificial General Intelligence, 2013. 4(2): 1-22
  9. Arnsten, A.F., The neurobiology of thought: the groundbreaking discoveries of Patricia Goldman-Rakic 1937-2003. Cereb Cortex, 2013. 23(10): 2269-81 doi: 10.1093/cercor/bht195
  10. Goghari, V.M., et al., The functional neuroanatomy of symptom dimensions in schizophrenia: a qualitative and quantitative review of a persistent question. Neurosci Biobehav Rev, 2010. 34(3): 468-86 doi: 10.1016/j.neubiorev.2009.09.004
  11. Melnik, T., et al., Efficacy and safety of atypical antipsychotic drugs (quetiapine, risperidone, aripiprazole and paliperidone) compared with placebo or typical antipsychotic drugs for treating refractory schizophrenia: overview of systematic reviews. Sao Paulo Medical Journal, 2010. 128: 141-66 http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-31802010000300007&nrm=iso
  12. Baars, B.J., Global workspace theory of consciousness: toward a cognitive neuroscience of human experience. Progress in brain research, 2005. 150: 45-53
  13. Repovs, G. and Baddeley, A., The multi-component model of working memory: explorations in experimental cognitive psychology. Neuroscience, 2006. 139(1): 5-21 doi: 10.1016/j.neuroscience.2005.12.061
  14. Haggard, P., Human volition: towards a neuroscience of will. Nat Rev Neurosci, 2008. 9(12): 934-46 doi: 10.1038/nrn2497
  15. Libet, B., et al., Time of conscious intention to act in relation to onset of cerebral activity (readiness-potential). The unconscious initiation of a freely voluntary act. Brain, 1983. 106 (Pt 3): 623-42 http://www.ncbi.nlm.nih.gov/pubmed/6640273
  16. Soon, C.S., et al., Unconscious determinants of free decisions in the human brain. Nat Neurosci, 2008. 11(5): 543-5 doi: 10.1038/nn.2112
  17. Espay, A.J. Frontal Lobe Syndromes. Medscape eMedicine 2012 [cited 2014, July 1]; Available from: http://emedicine.medscape.com/article/1135866-clinical – showall.
  18. Castells, X., et al., Amphetamines for Attention Deficit Hyperactivity Disorder (ADHD) in adults. Cochrane Database Syst Rev, 2011(6): CD007813 doi: 10.1002/14651858.CD007813.pub2
  19. Hodgkins, P., et al., The Pharmacology and Clinical Outcomes of Amphetamines to Treat ADHD. CNS drugs, 2012. 26(3): 245-68
  20. Bonn, G.B., Re-conceptualizing free will for the 21st century: acting independently with a limited role for consciousness. Front Psychol, 2013. 4: 920 doi: 10.3389/fpsyg.2013.00920
  21. Dixon, T., “Emotion”: The History of a Keyword in Crisis. Emot Rev, 2012. 4(4): 338-44 doi: 10.1177/1754073912445814
  22. Watkins, A. Being brilliant every single day – Part 1. 2012 [cited 2 March 2012]; Available from: http://www.youtube.com/watch?v=q06YIWCR2Js.
  23. Tamietto, M. and de Gelder, B., Neural bases of the non-conscious perception of emotional signals. Nat Rev Neurosci, 2010. 11(10): 697-709 doi: 10.1038/nrn2889
  24. Caspi, A., et al., Genetic sensitivity to the environment: the case of the serotonin transporter gene and its implications for studying complex diseases and traits. Am J Psychiatry, 2010. 167(5): 509-27 doi: 10.1176/appi.ajp.2010.09101452
  25. Felten, A., et al., Genetically determined dopamine availability predicts disposition for depression. Brain Behav, 2011. 1(2): 109-18 doi: 10.1002/brb3.20
  26. Beauregard, M. and Paquette, V., Neural correlates of a mystical experience in Carmelite nuns. Neurosci Lett, 2006. 405(3): 186-90 doi: 10.1016/j.neulet.2006.06.060
  27. Mohandas, E., Neurobiology of spirituality. Mens Sana Monogr, 2008. 6(1): 63-80 doi: 10.4103/0973-1229.33001
  28. Kahnt, T., et al., Connectivity-based parcellation of the human orbitofrontal cortex. J Neurosci, 2012. 32(18): 6240-50 doi: 10.1523/JNEUROSCI.0257-12.2012
  29. Plassmann, H., et al., Appetitive and aversive goal values are encoded in the medial orbitofrontal cortex at the time of decision making. J Neurosci, 2010. 30(32): 10799-808 doi: 10.1523/JNEUROSCI.0788-10.2010
  30. Devinsky, O. and Lai, G., Spirituality and religion in epilepsy. Epilepsy Behav, 2008. 12(4): 636-43 doi: 10.1016/j.yebeh.2007.11.011
  31. Persinger, M.A., et al., The electromagnetic induction of mystical and altered states within the laboratory. Journal of Consciousness Exploration & Research, 2010. 1(7)
  32. Granqvist, P., et al., Sensed presence and mystical experiences are predicted by suggestibility, not by the application of transcranial weak complex magnetic fields. Neurosci Lett, 2005. 379(1): 1-6 http://www.ncbi.nlm.nih.gov/pubmed/15849873
  33. Kapogiannis, D., et al., Cognitive and neural foundations of religious belief. Proc Natl Acad Sci U S A, 2009. 106(12): 4876-81 doi: 10.1073/pnas.0811717106
  34. Norenzayan, A., et al., Mentalizing deficits constrain belief in a personal God. PLoS One, 2012. 7(5): e36880 doi: 10.1371/journal.pone.0036880
  35. Maguire, E.A., et al., London taxi drivers and bus drivers: a structural MRI and neuropsychological analysis. Hippocampus, 2006. 16(12): 1091-101 doi: 10.1002/hipo.20233
  36. Holzel, B.K., et al., Mindfulness practice leads to increases in regional brain gray matter density. Psychiatry Res, 2011. 191(1): 36-43 doi: 10.1016/j.pscychresns.2010.08.006
  37. Bunge, M., The Mind-Body Problem, in Matter and Mind. 2010, Springer Netherlands. p. 143-57.

Postscript: There is a lot more to String Theory, and anyone interested in knowing more would be well served by reviewing the transcripts or watching the PBS series “The Elegant Universe”, hosted by Brian Greene.

Dr Caroline Leaf and the 98 Percent Myth

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Dr Caroline Leaf believes that nearly all our diseases come from our thoughts.

Dr Caroline Leaf believes that nearly all our diseases come from our thoughts.

In the hustle and bustle of daily life, most people wouldn’t stop to consider what makes people sick.  In my profession, I get a front row seat.

In the average week, I get to see a number of different things.  Mostly “coughs, colds and sore holes” as the saying goes, although there are some rarer things too.  And sometimes, people present with problems that aren’t for the faint of heart (or stomach – beware of nail guns is all I can say).

Normally, the statistics of who comes in with what doesn’t make it beyond the desk of the academic or health bureaucrat.  The numbers aren’t as important as the people they represent.

But to Dr Caroline Leaf, Communication Pathologist and self-titled Cognitive Neuroscientist, the numbers are all important.  To support her theory of toxic thoughts, Dr Leaf has stated that “75 to 98% of mental and physical (and behavioural) illness comes from one’s thought life” [1: p37-38].  She has repeated that statement on her website, on Facebook, and at seminars.

As someone with a front row seat to the illnesses people have, I found such a statement perplexing.  In the average week, I don’t see anywhere near that number.  In general practices around Australia, the number of presentations for psychological illnesses is only about eight percent [2].

But Australian general practice is a small portion of medicine compared to the world’s total health burden.  Perhaps the global picture might be different?  The World Health Organization, the global authority on global health, published statistics in November 2013 on the global DALY statistics [3] (a DALY is a Disability Adjusted Life Year).  According to the WHO, all Mental and Behavioural Disorders accounted for only 7.2% of the global disease burden.

You don’t need a statistics degree to know that seven percent is a long way from seventy-five percent (and even further from 98%).

Perhaps a large portion of the other ninety-three percent of disease that was classified as physical disease was really caused by toxic thoughts?  Is that possible?  In short: No.

When considered in the global and historical context, the vast majority of illness is related to preventable diseases that are so rare in the modern western world because of generations of high quality public health and medical care.

In a recent peer-reviewed publication, Mara et al state, “At any given time close to half of the urban populations of Africa, Asia, and Latin America have a disease associated with poor sanitation, hygiene, and water.” [4] Bartram and Cairncross write that “While rarely discussed alongside the ‘big three’ attention-seekers of the international public health community—HIV/AIDS, tuberculosis, and malaria—one disease alone kills more young children each year than all three combined. It is diarrhoea, and the key to its control is hygiene, sanitation, and water.” [5] Hunter et al state that, “diarrhoeal disease is the second most common contributor to the disease burden in developing countries (as measured by disability-adjusted life years (DALYs)), and poor-quality drinking water is an important risk factor for diarrhoea.” [6]

Diarrhoeal disease in the developing world – the second most common contributor to disease in these countries, afflicting half of their population – has nothing to do with thought.  It’s related to the provision of toilets and clean running water.

We live in a society that prevents half of our illnesses because of internal plumbing.  Thoughts seem to significantly contribute to disease because most of our potential illness is prevented by our clean water and sewerage systems.  Remove those factors and thought would no longer appear to be so significant.

In the same manner, modern medicine has become so good at preventing diseases that thought may seem to be a major contributor, when in actual fact, most of the work in keeping us all alive has nothing to do with our own thought processes.  Like sanitation and clean water, the population wide practices of vaccination, and health screening such as pap smears, have also significantly reduced the impact of preventable disease.

Around the world, “Recent estimates of the global incidence of disease suggest that communicable diseases account for approximately 19% of global deaths” and that “2.5 million deaths of children annually (are) from vaccine-preventable diseases.” [7] Again, that’s a lot of deaths that are not related to thought life.

Since 1932, vaccinations in Australia have reduced the death rate from vaccine-preventable diseases by 99% [8].  Epidemiological evidence shows that when vaccine rates increase, sickness from communicable diseases decrease [9: Fig 2, p52 & Fig 8, p67].

Population based screening has also lead to a reduction in disease and death, especially in the case of population screening by pap smears for cervical cancer.  Canadian public health has some of the best historical figures on pap smear screening and cervical cancer. In Canada, as the population rate of pap smear screening increased, the death rate of women from cervical cancer decreased.  Overall, pap smear screening decreased the death rate from cervical cancer by 83%, from a peak of 13.5/100,000 in 1952 to only 2.2/100,000 in 2006, despite an increase in the population and at-risk behaviours for HPV infection (the major risk factor for cervical cancer) [10].

And around the world, the other major cause of preventable death is death in childbirth.  The risk of a woman dying in childbirth is a staggering one in six for countries like Afghanistan [11] which is the same as your odds playing Russian Roulette.  That’s compared to a maternal death rate of one in 30,000 in countries like Sweden.  The marked disparity is not related to the thought life of Afghani women in labour.  Countries that have a low maternal death rate all have professional midwifery care at birth.  Further improvements occur because of better access to hospital care, use of antibiotics, better surgical techniques, and universal access to the health system [11].  Again, unless one’s thought life directly changes the odds of a midwife appearing to help you deliver your baby, toxic thoughts are irrelevant as a cause of illness and death.

Unfortunately for Dr Leaf, her statement that “75 to 98 percent of mental, physical and behavioural illnesses come from toxic thoughts” is a myth, a gross exaggeration of the association of stress and illness.

In the global and historical context of human health, the majority of illness is caused by infectious disease, driven by a lack of infrastructure, public health programs and nursing and medical care.  To us in the wealthy, resource-rich western world, it may seem that our thought life has a significant effect on our health.  That’s only because we have midwives, hospitals, public health programs and internal plumbing, which stop the majority of death and disease before they have a chance to start.

Don’t worry about toxic thoughts.  Just be grateful for midwives and toilets.

References

1.         Leaf, C.M., Switch On Your Brain : The Key to Peak Happiness, Thinking, and Health. 2013, Baker Books, Grand Rapids, Michigan:

2.         FMRC. Public BEACH data. 2010  [cited 16JUL13]; Available from: <http://sydney.edu.au/medicine/fmrc/beach/data-reports/public%3E.

3.         World Health Organization, GLOBAL HEALTH ESTIMATES SUMMARY TABLES: DALYs by cause, age and sex, GHE_DALY_Global_2000_2011.xls, Editor 2013, World Health Organization,: Geneva, Switzerland.

4.         Mara, D., et al., Sanitation and health. PLoS Med, 2010. 7(11): e1000363 doi: 10.1371/journal.pmed.1000363

5.         Bartram, J. and Cairncross, S., Hygiene, sanitation, and water: forgotten foundations of health. PLoS Med, 2010. 7(11): e1000367 doi: 10.1371/journal.pmed.1000367

6.         Hunter, P.R., et al., Water supply and health. PLoS Med, 2010. 7(11): e1000361 doi: 10.1371/journal.pmed.1000361

7.         De Cock, K.M., et al., The new global health. Emerg Infect Dis, 2013. 19(8): 1192-7 doi: 10.3201/eid1908.130121

8.         Burgess, M., Immunisation: A public health success. NSW Public Health Bulletin, 2003. 14(1-2): 1-5

9.         Immunise Australia, Myths and Realities. Responding to arguments against vaccination, A guide for providers. 5th ed. 2013, Commonwealth of Australia, Department of Health and Ageing, Canberra:

10.       Dickinson, J.A., et al., Reduced cervical cancer incidence and mortality in Canada: national data from 1932 to 2006. BMC Public Health, 2012. 12: 992 doi: 10.1186/1471-2458-12-992

11.       Ronsmans, C., et al., Maternal mortality: who, when, where, and why. Lancet, 2006. 368(9542): 1189-200 doi: 10.1016/S0140-6736(06)69380-X

Dr Caroline Leaf – Contradicted by the latest research

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This is my most popular post by far.  I truly appreciate the support and interest in this post, but I’ve discovered and documented a lot more about Dr Leaf’s ministry in the last two years.  I welcome you to read this post, but if you’d like a more current review of the ministry of Dr Caroline Leaf, a new and improved version is here:
Dr Caroline Leaf – Still Contradicted by the Latest Evidence, Scripture & Herself

* * * * *

Mr Mac Leaf, the husband of Dr Caroline Leaf, kindly took the time to respond to my series of posts on the teachings of Dr Leaf at Kings Christian Centre, on the Gold Coast, Australia, earlier this month. As I had intended, and as Mr Leaf requested, I published his  reply, complete and unabridged (here).

This blog is my reply.  It is heavily researched and thoroughly referenced.  I think it’s fair to say that while Dr Leaf draws her conclusions from some scientific documents, there is more than enough research that contradicts her statements and opinions.  I have only listed a small fraction, and only on some of the points she raised.

In fairness, the fields of neurology and neuroscience are vast and rapidly expanding, and it is impossible for one person to cover all of the literature on every subject.  This applies to myself and Dr Leaf.  However, I believe that the information I have read, and referenced from the latest peer-reviewed scholarly works, do not support Dr Leaf’s fundamental premises.  If I am correct, then the strength and validity of Dr Leaf’s published works should be called into question.

As before, I welcome any reply or rebuttal that Dr Leaf wishes to make, which I will publish in full if she requests.  In the interests of healthy public debate, and encouraging people to make their own informed decisions on the teachings of Dr Leaf, any comments regarding the response of Mr Leaf, Dr Leaf or myself, are welcome provided they are constructive.

This is a bit of a lengthy read, but I hope it is worthwhile.

Dear Mr Leaf,

Thank you very much for taking the time out to reply to some of the points raised in my blog.  I am more than happy to publish your response, and to publish any response you wish to make public.

ON INFORMED DECISIONS

I published my blog posts to open up discussion on the statements made by Dr Leaf at the two meetings that I attended at Kings Christian Centre on the Gold Coast.  As you rightly point out, people should be able to make informed decisions.  A robust discussion provides the information required for people to make an informed choice.  Any contributions to this discussion from either yourself or Dr Leaf would be most welcome.

I apologise if you interpreted my blogs as judgemental, or if you believe there are any misunderstandings.  You may or may not have read my final two paragraphs from the third post, in which I acknowledged that I may have misunderstood where she was coming from, but that I would welcome her response.  If there were any misunderstandings, it is likely because Dr Leaf did not make any attempt to reference any of the statements she made on the day.  You may argue that she was speaking to a lay audience, and referencing is therefore not necessary.  However, I have been to many workshops for the lay public by university professors, who have extensively referenced their information during their presentations.  A lay audience does not preclude providing references.  Rather, it augments the speakers authority and demonstrates the depth of their knowledge on the subject at hand.

YOUR DEFENCE

It’s interesting that you feel the need to resort to defence by association, and Ad Hominem dismissal as your primary counter to the points I raised.

Can you clarify how attending the same university as Dr Christaan Barnard, or a Nobel laureate, endorses her arguments or precludes her from criticism?  I attended the University of Queensland where Professor Ian Frazer was based.  He developed the Human Papilloma Virus vaccine and was the 2006 Australian of the Year.  Does that association enhance my argument?

Can you also clarify why a reference from a colleague was preferred to letting Dr Leaf’s statements and conclusions speak for themselves?  Dr Amua-Quarshie’s CV is certainly very impressive, no doubt about that, although he doesn’t list the papers he’s published.  (I’m assuming that to hold the title of Adjunct Professor, he’s published peer-reviewed articles.  Is he willing to list them, for the record?)

Whatever his credentials, his endorsement means very little, since both Dr Leaf and Dr Amua-Quarshie would know from their experience in research that expert opinion is one of the lowest forms of evidence, second worst only to testimonials [1].  Further, both he and Dr Leaf are obviously close friends which introduces possible bias.  His endorsement is noteworthy, but it can not validate every statement made by Dr Leaf.  Her statements should stand up on their own through the rigors of critical analysis.

On the subject of evidence, disparaging your critics is not a substitute for answering their criticism.  Your statement, “By your comments it is obvious that you have not kept up to date with the latest Scientific research” is an assumption that is somewhat arrogant, and ironic since Dr Leaf is content to use superseded references dating back to 1979 to justify her current hypotheses.

DR LEAF’S EVIDENCE

In the blog to which you referred, Dr Leaf makes a number of statements that are intended to support her case.  These include the following.

“A study by the American Medical Association found that stress is a factor in 75% of all illnesses and diseases that people suffer from today.”  She fails to reference this study.

“The association between stress and disease is a colossal 85% (Dr Brian Luke Seaward).”   But again, she fails to reference the quote.

“The International Agency for Research on Cancer and the World Health Organization has concluded that 80% of cancers are due to lifestyles and are not genetic, and they say this is a conservative number (Cancer statistics and views of causes Science News Vol.115, No 2 (Jan.13 1979), p.23).”  It’s good that she provides a reference to her statement.  However, referencing a journal on genetics from 1979 is the equivalent of attempting to use the land-speed record from 1979 to justify your current preference of car.  The technology has advanced significantly, and genetic discoveries are lightyears ahead of where they were more than three decades ago.

“According to Dr Bruce Lipton (The Biology of Belief, 2008), gene disorders like Huntington’s chorea, beta thalassemia, cystic fibrosis, to name just a few, affect less than 2% of the population. This means the vast majority of the worlds population come into this world with genes that should enable the to live a happy and healthy life. He says a staggering 98% of diseases are lifestyle choices and therefore, thinking.”  Even if it’s true that Huntingtons, CF etc account for 2% of all illnesses, they account for only a tiny fraction of genetic disease.  And concluding that the remaining 98% must therefore be lifestyle related is overly simplistic.  It ignores the genetic influence on all other diseases, other congenital, and environmental causes of disease.  I will fully outline this point soon.

Similarly, “According to W.C Willett (balancing lifestyle and genomics research for disease prevention Science (296) p 695-698, 2002) only 5% of cancer and cardiovascular patients can attribute their disease to hereditary factors.”  Science is clear that genes play a significant role in the development of cardiovascular disease and most cancers, certainly greater than 5%.  Again, I will discuss this further soon.

“According to the American Institute of health, it has been estimated that 75 – 90% of all visits to primary care physicians are for stress related problems (http://www.stress.org/americas.htm). Some of the latest stress statistics causing illness as a result of toxic thinking can be found at: http://www.naturalwellnesscare.com/stress-statistics.html”  These websites not peer-reviewed, and both suffer from a blatant pro-stress bias.

You’ll also have to forgive my confusion, but Dr Leaf also wrote, “Dr H.F. Nijhout (Metaphors and the Role of Genes and Development, 1990) genes control biology and not the other way around.”  So is she saying that genes DO control development?

EVIDENCE CONTRADICTING DR LEAF

Influence Of Thought On Health

Dr Leaf has categorically stated that “75 to 98% of all illnesses are the result of our thought life” on a number of occasions.  She repeated the same statement in her most recent book so it is something she is confident in.  However, in order to be true, this fact must be consistent across the whole of humanity.

And yet, in a recent peer-reviewed publication, Mara et al state, “At any given time close to half of the urban populations of Africa, Asia, and Latin America have a disease associated with poor sanitation, hygiene, and water.” [2]  Bartram and Cairncross write that “While rarely discussed alongside the ‘big three’ attention-seekers of the international public health community—HIV/AIDS, tuberculosis, and malaria—one disease alone kills more young children each year than all three combined. It is diarrhoea, and the key to its control is hygiene, sanitation, and water.” [3]  Hunter et al state that, “diarrhoeal disease is the second most common contributor to the disease burden in developing countries (as measured by disability-adjusted life years [DALYs]), and poor-quality drinking water is an important risk factor for diarrhoea.” [4]

Toilets and clean running water have nothing to do with stress or thought.  We live in a society that essentially prevents more than half of our illnesses because of internal plumbing, with additional benefits from vaccination and population screening.  If thoughts have any effect on our health, they are artificially magnified by our clean water and sewerage systems.  Remove those factors and any effects of thought on our health disappear from significance.  Dr Leaf’s assertion that 75 to 98% of human illness is thought-related is a clear exaggeration.

Let me be clear – I understand the significance of stress on health and the economy, but it is not the cause of 75-98% of all illnesses.  I’m not sure if there is a similar study in the US, but the latest Australian data suggests that all psychological illness only counts for 8% of visits to Australian primary care physicians [5].

In terms of cancer, I don’t have time to exhaustively list every cancer but of the top four listed in the review “Cancer Statistics 2013” [6] , here are the articles that list the gene x environment interactions:

  1. PROSTATE – There are only two risk factors for prostate cancer, familial aggregation and ethnic origin. No dietary or environmental cause has yet been identified [7].  It is most likely caused by multiple genes at various loci [8].
  2. BREAST – Genes make up 25% of the risk factors for breast cancer, and significantly interacted with parity (number of children born) [9].
  3. LUNG/BRONCHUS – Lung cancer is almost exclusively linked to smoking, but nicotine addiction has a strong hereditary link (50-75% genetic susceptibility) [10].
  4. COLORECTUM – Approximately one third of colorectal cancer is genetically linked [11].

So the most common cancer is not linked to any environmental factors at all, and the others have genetic influences of 25% to more than 50%.  This is far from being 2% or 5% as Dr Leaf’s sources state.

Also in terms of heart disease, the INTERHEART trial [12] lists the following as significant risk factors, and I have listed the available gene x environment interaction studies that have been done on these too:

  1. HIGH CHOLESTEROL – Genetic susceptibility accounts for 40-60% of the risk for high cholesterol [13].
  2. DIABETES – Genetic factors account for 88% of the risk for type 1 diabetes [14].  There is a strong genetic component of the risk of type 2 diabetes with 62-70% being attributable to genetics [15, 16].
  3. SMOKING – nicotine addiction has a strong hereditary link (50-75% genetic susceptibility) [10].
  4. HYPERTENSION – While part of a much greater mix of variables, genetics are still thought to contribute between 30% and 50% to the risk of developing high blood pressure [17].

So again, while genes are a part of a complex system, it is clear from the most recent evidence that genetics account for about 50% of the risk for cardiovascular disease, which again is a marked difference between the figures that Dr Leaf is using to base her assertions on.

Atrial Natriuretic Peptide

I am aware of research that’s studied the anxiolytic properties of Atrial Natriuretic Peptide.  For example, Wiedemann et al [18] did a trial using ANP to truncate panic attacks.  However, these experiments were done on only nine subjects, and the panic attacks were induced by cholecystokinin.  As such, the numbers are too small to have any real meaning.  And the settling is completely artificial.  Just as CCK excretion does not cause us all to have panic attacks every time we eat, ANP does not provide anxiolysis in normal day to day situations.  Besides, if ANP were really effective at reducing anxiety, then why do people suffering from congestive cardiac failure, who have supraphysiological levels of circulating ANP [19] , also suffer from a higher rate of anxiety and panic disorders than the general population? [20]

The Heart As A Mini-Brain

As for Heartmath, they advance the notion of the heart being a mini-brain to give themselves credibility.  It’s really no different to an article that I read the other day from a group of gut researchers [21] – “‘The gut is really your second brain,’ Greenblatt said. ‘There are more neurons in the GI tract than anywhere else except the brain.’”  The heart as a mini-brain and the gut as a mini-brain are both figurative expressions.  Neither are meant to be taken literally.  I welcome Dr Leaf to tender any further evidence in support of her claim.

Hard-Wired For Optimism

As for being wired for optimism, the brain is likely pre-wired with a template for all actions and emotions, which is the theory of protoconsciousness [22].  Indeed, neonatal reflexes often reflect common motor patterns.  If this is true, then the brain is pre-wired for both optimism and love, but also fear.  This explains the broad role of the amygdala in emotional learning [23] including fear learning.  It also means that a neonate needs to develop both love and fear.

A recent paper showed that the corticosterone response required to learn fear is suppressed in the neonate to facilitate attachment, but with enough stress, the corticosterone levels build to the point where amygdala fear learning can commence [24].  The fear circuits are already present, only their development is suppressed.  Analysis of the cohort of children in the Bucharest Early Intervention Project showed that negative affect was the same for both groups.  However positive affect and emotional reactivity was significantly reduced in the institutionalised children [25].  If the brain is truly wired for optimism and only fear is learned, then positive emotional reactivity should be the same in both groups and the negative affect should be enhanced in the institutionalised cohort.  That the result is reversed confirms that neonates and infants require adequate stimulation of both fear and love pathways to grow into an emotionally robust child, because the brain is pre-wired for both but requires further stimulation for adequate development.

The Mind-Brain Link

If the mind controls the brain and not the other way around as Dr Leaf suggests, why do anti-depressant medications correct depression or anxiety disorders?  There is high-level evidence to show this to be true [26-28].  The same can be said for recent research to show that medications which enhance NDMA receptors have been shown to improve the extinction of fear in anxiety disorders such as panic disorder, OCD, Social Anxiety Disorder, and PTSD [29].

If the mind controls the brain and not the other way around as Dr Leaf suggests, why do some people with acquired brain injuries or brain tumours develop acute personality changes or thought disorders?  Dr Leaf has done PhD research on patients with closed head injuries and treated them in clinical settings according to her CV.  She must be familiar with this effect.

One can only conclude that there is a bi-directional effect between the brain and the stream of thought, which is at odds with Dr Leaf’s statement that the mind controls the brain and not the other way around.

FURTHER CLARIFICATION

One further thing.  Can you clarify which of Dr Leaf’s peer-reviewed articles have definitively shown the academic improvement in the cohort of 100,000 students, as you and your referee have stated?  And can you provide a list of articles which have cited Dr Leaf’s Geodesic Information Processing Model?  Google Scholar did not display any articles that had cited it, which must be an error on Google’s part.  If her theory is widely used as you say, it must have been extensively cited.

I understand that you are both busy, but I believe that I have documented a number of observations, backed by recent peer-reviewed scientific literature, which directly contradict Dr Leaf’s teaching.  I have not had a chance to touch on many, many other points of disagreement.

For the benefit of Dr Leaf’s followers, and for the scientific and Christian community at large, I would appreciate your response.

I would be grateful if you could respond to the points raised and the literature which supports it, rather than an Ad Hominem dismissal or further defense by association.

Dr C. Edward Pitt

REFERENCES

1. Fowler, G., Evidence-based practice: Tools and techniques. Systems, settings, people: Workforce development challenges for the alcohol and other drugs field, 2001: 93-107.

2. Mara, D., et al., Sanitation and health. PLoS Med, 2010. 7(11): e1000363.

3. Bartram, J. and Cairncross, S., Hygiene, sanitation, and water: forgotten foundations of health. PLoS Med, 2010. 7(11): e1000367.

4. Hunter, P.R., et al., Water supply and health. PLoS Med, 2010. 7(11): e1000361.

5. FMRC. Public BEACH data. 2010  16JUL13]; Available from: <http://sydney.edu.au/medicine/fmrc/beach/data-reports/public&gt;.

6. Siegel, R., et al., Cancer statistics, 2013. CA Cancer J Clin, 2013. 63(1): 11-30.

7. Cussenot, O. and Valeri, A., Heterogeneity in genetic susceptibility to prostate cancer. Eur J Intern Med, 2001. 12(1): 11-6.

8. Alberti, C., Hereditary/familial versus sporadic prostate cancer: few indisputable genetic differences and many similar clinicopathological features. Eur Rev Med Pharmacol Sci, 2010. 14(1): 31-41.

9. Nickels, S., et al., Evidence of gene-environment interactions between common breast cancer susceptibility loci and established environmental risk factors. PLoS Genet, 2013. 9(3): e1003284.

10. Berrettini, W.H. and Doyle, G.A., The CHRNA5-A3-B4 gene cluster in nicotine addiction. Mol Psychiatry, 2012. 17(9): 856-66.

11. Hutter, C.M., et al., Characterization of gene-environment interactions for colorectal cancer susceptibility loci. Cancer Res, 2012. 72(8): 2036-44.

12. Yusuf, S., et al., Effect of potentially modifiable risk factors associated with myocardial infarction in 52 countries (the INTERHEART study): case-control study. Lancet, 2004. 364(9438): 937-52.

13. Asselbergs, F.W., et al., Large-scale gene-centric meta-analysis across 32 studies identifies multiple lipid loci. Am J Hum Genet, 2012. 91(5): 823-38.

14. Wu, Y.L., et al., Risk factors and primary prevention trials for type 1 diabetes. Int J Biol Sci, 2013. 9(7): 666-79.

15. Ali, O., Genetics of type 2 diabetes. World J Diabetes, 2013. 4(4): 114-23.

16. Murea, M., et al., Genetic and environmental factors associated with type 2 diabetes and diabetic vascular complications. Rev Diabet Stud, 2012. 9(1): 6-22.

17. Kunes, J. and Zicha, J., The interaction of genetic and environmental factors in the etiology of hypertension. Physiol Res, 2009. 58 Suppl 2: S33-41.

18. Wiedemann, K., et al., Anxiolyticlike effects of atrial natriuretic peptide on cholecystokinin tetrapeptide-induced panic attacks: preliminary findings. Arch Gen Psychiatry, 2001. 58(4): 371-7.

19. Ronco, C., Fluid overload : diagnosis and management. Contributions to nephrology,. 2010, Basel Switzerland ; New York: Karger. viii, 243 p.

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Dr Caroline Leaf – Serious questions, few answers (Part 3) – “Flirting with heresy”

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Following on from the last 2 posts discussing the various teaching points of Dr Caroline Leaf at Kings Christian Church, here is my final post on the points that she raised.  Tonight, I conclude by proposing that in equating ‘toxic’ thoughts with sin, she seriously weakens her own argument, or she flirts with heresy.

TOXIC THOUGHTS ARE SIN

Probably the most disturbing of all she discussed was her point blank statement that, “Toxic thoughts are sin.”

This is an astounding claim, and it was said in such an off-handed manner. It was like she threw a grenade and calmly moved on. Her claim not only has psychological ramifications, but deep theological connotations.

Her statement has the effect of ADDING to the stress response of her audience. Indeed, it sets up a feedback loop of self-perpetualising existential distress – the spiritual struggle switch. Crum et al (2013) showed that negatively framing the concept of stress leads to an increase in the subjects stress response. What could be more stressing that telling a christian that they have sinned every time that have had a persistent stress?  More stress is then equated with more ‘sin’ which then gives rise to even more stress. And so the cycle continues.

She then attempted to redeem her statement by declaring that we can transcend the guilt from the sin of stress, because her 21-day brain detox program would fix it. But on the surface, it seems an arbitrary premise. Inducing guilt to then offer to fix it is like a supermarket marking up a price so they can claim to offer a discount when they reduce it again.

More importantly though, in making the link between stress and sin, she brings herself undone. She either unravels her entire argument, or she flirts with heresy. Because if a thought process which results in prolonged or severe fear/stress is a sin, then Jesus himself sinned.

In the Garden of Gethsemane, the gospels record that Jesus, the spotless lamb of God, about to be crucified for the sins of all mankind, was “overwhelmed with sorrow to the point of death” (Mark 14:34, Matthew 26:38), and became so distressed by the ordeal he was about to endure that he literally sweat drops of blood (Luke 22:44).

Where do you think Jesus was on the stress spectrum according to those accounts? I’d wager that it wasn’t “healthy stress”.Rev Bob Deffinbaugh wrote that,

“Jesus spent what appears to be at least three agonizing hours in prayer.” He also noted that, “Never before have we seen Jesus so emotionally distraught. He has faced a raging storm on the Sea of Galilee, totally composed and unruffled. He has faced demonic opposition, satanic temptation, and the grilling of Jerusalem’s religious leaders, with total composure. But here in the Garden, the disciples must have been greatly distressed by what (little) they saw. Here, Jesus cast Himself to the ground, agonizing in prayer.” (https://bible.org/seriespage/garden-gethsemane-luke-2239-46)

There is no other way to explain it – Jesus suffered severe and prolonged mental anguish to the point that it had physical effects. By Dr Leaf’s definition (Leaf 2009, p19), Jesus had “toxic” thoughts. So the crux is: either toxic thoughts and emotions are sinful, in which case Jesus was a sinner and our salvation is invalid, or toxic thoughts and emotions are not sinful, which directly contradicts her teaching.

There is at least one further example from the life of Jesus that significantly weakens Dr Leafs definition of ‘toxic’ thoughts. In her book, Dr Leaf states, “hostility and rage are at the top of the list of toxic emotions”, and that “Stress is the direct result of toxic thinking.” (Leaf 2009, p29-30)

In John 2:13-17, it says, “When it was almost time for the Jewish Passover, Jesus went up to Jerusalem. In the temple courts he found people selling cattle, sheep and doves, and others sitting at tables exchanging money. So he made a whip out of cords, and drove all from the temple courts, both sheep and cattle; he scattered the coins of the money changers and overturned their tables. To those who sold doves he said, “Get these out of here! Stop turning my Father’s house into a market!” His disciples remembered that it is written: “Zeal for your house will consume me.”

So Jesus saw the sellers and the money exchangers, then in a pre-meditated way, took small cords and fashioned a whip out of them, then proceeded to use that whip to violently and aggressively overturn the tables of the merchants and spill the money of the money changers. John adds a post-script – “Zeal for your house will consume me.”  So Jesus wasn’t mincing words. He drove them out of the temple in a rage.

Again, was Jesus acting in sin?  Of course not.  Instead, perhaps God has designed normal human beings to experience rage, anger and stress – emotions that are not curses passed down in genetic material and are not learned behaviours as a result of our sin nature.

Further, God himself displayed anger.  God also made us in his image, and in his likeness. Dr Leaf stated that we were designed to function in optimism and love, and again, negative emotions like anger and fear are learnt from living in sin. Yet it is interesting that God the Father regularly kindled his wrath, and smote Israelites or their enemies (Numbers 11:33, Deuteronomy 11:16-17, and in 2 Kings 23:25-27, “Notwithstanding the Lord turned not from the fierceness of his great wrath, wherewith his anger was kindled against Judah, because of all the provocations that Manasseh had provoked him withal.”)

If God regularly displayed anger throughout the Old Testament, and Jesus displayed it in the New Testament, then anger and rage can not be the perversion of God’s ultimate design as Dr Leaf proposes.

Therefore, ‘toxic’ thought is NOT sin, because Jesus suffered prolonged mental stress and anguish and he did not sin.  Emotions that are deemed to be toxic by Dr Leaf and her definition are not toxic, since both God and Jesus displayed them and they did not and do not sin. Such a suggestion is incongruent with the Christian faith.

We were made in the image of God, so therefore we mirror all the emotions of God, which includes anger.  This shows that Dr Leaf’s proposals and the assumptions on which they are based, are incongruent with a logical interpretation of scripture.

In conclusion, Dr Leaf has been gathering quite a following.  From the pulpit at least, her claims of evidence of studies from peer-reviewed sources have been lacking. From what I saw on Sunday last, her reputation is excessive, her arguments unsupported and her theology is questionable at best, dangerous at worst.

Personally, I would welcome Dr Leaf’s response to these posts.  I have written these posts over a few days from her teaching at one church, so perhaps I have misunderstood her.  I have not been able to go through all of her books in such a short time, so she may have references to her teaching.  But she needs to clarify each question that I’ve raised and respond with current peer-reviewed science and sound theological resources.

References

Crum, A. J., P. Salovey and S. Achor (2013). “Rethinking stress: the role of mindsets in determining the stress response.” J Pers Soc Psychol 104(4): 716-733.

Karatsoreos, I. N. and B. S. McEwen (2011). “Psychobiological allostasis: resistance, resilience and vulnerability.” Trends Cogn Sci 15(12): 576-584.

Leaf, C. (2009). Who Switched Off My Brain? Controlling toxic thoughts and emotions. Southlake, TX, USA, Inprov, Ltd.

Fear: Friend or Foe?

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Fear.  Should we run, fight, or think?

I was lazily wasting time at Zarraffas this afternoon, and while I was savouring the richness and depth of my triple masai mocha, I was filling the time by flicking through Facebook.

I came upon a blog post by one of the best thinkers and writers I’m personally acquainted with, one Ruth Limkin, who shared the story of how she was given an opportunity to snorkel in a pristine area of ocean in the South Pacific that is limited to only a handful of people, such is the fragile beauty of the ecosystem there.  As she started swimming into the warm, calm, azure waters, she felt this sudden dread.

Five years ago in a similar situation, she misjudged the current, was swept into some coral, and sustained a laceration to her knee.  This left a lot of blood in the water which, quite reasonably, made her think that she had suddenly become shark bait.  She made it back to shore otherwise unscathed. But it left her with the implicit memory of that event.

This year, despite the obviously calm surroundings, she recalled that fear. Her brain told her to get out of there.  She did manage to overcome her fear though, and enjoyed the snorkelling!

Her lesson was that the pain of yesterday can become todays fear, which robs tomorrow of its promise.

I don’t disagree with Ruth.  I’m not intelligent enough to do that.  But I guess I come from a more medical and analytical perspective of this phenomenon, and I wanted to flesh out her point a bit further.

We all feel it at sometime or another – your heart pounds faster and heavier in your chest. Your breathing gets faster. Your muscles tighten. And your brain either says, “Run” or “Fight”, or sometimes it says nothing at all and we simply freeze up.

The human fear response is both rational and irrational.  We usually don’t understand why we are faced with conflicting realities of internal anxiety and external tranquility, feeling scared while looking at calm clear waters.  Sometimes when we take a step back, we can gain some understanding of why we have reacted the way we did, and cognitively overcome our fear.

B-grade pop-psychologists make us believe that courage is the absence of fear, and that the way to move forward is to eliminate or repress your fears.  But that approach is wrong for a couple of reasons.

There is a good reason why we have fear conditioning.  There is a part of the brain called the limbic system, which is integral to emotional processing.  Central to this is the amygdala, which is responsible for adding emotions to our experiences, especially fear and anger.  When something happens that has real or perceived negative consequences (we experience pain, or we think that there is a high chance that we will experience pain) the amygdala pairs that aversive sensation with the memory of the total experience.  This helps us learn from our mistakes [1].

For example, if a pre-historic man was walking through a forest and came across a sabre-toothed tiger, the fight-or-flight response would help him escape.  But the amygdala would attach the memory of the emotion to the memory of the event itself.  Next time the man walked through a similar forest, or even recalled that event in his mind, the emotion of the memory would also be recalled.  This is why Ruth felt uneasy despite the lack of danger.  Her surroundings triggered the emotional memory of the previous snorkelling experience.

But while unpleasant, fear does confer a survival advantage.  Without the same emotion being recalled, we wouldn’t remember what situations were dangerous and which were safe.  Recalling the emotion and realising there may be sabre-toothed tigers around, or strong currents and sharks, means that there is a much smaller chance of us becoming lunch.

There are two pathways in the brain that are involved in the fear response.  The direct pathway goes from the senses to the amygdala, bypassing the thinking parts of our brain entirely.  Again, this confers a survival advantage as the quicker you can prepare yourself for danger, the more likely you are to survive it.  The signal is not properly analysed, but it doesn’t need to be.  It is better to be wrong and live than to be right and eaten by something.

The second pathway from the senses to the cerebral cortex then back to the amygdala is more precise, but it is slower than the direct path.  It can downgrade the fear response if it is not appropriate.  Well, it can in most people.  Anxiety and panic disorders arise when the balance between the direct and indirect pathways is skewed in the direction of the amygdala.

If you think you may have an anxiety disorder or panic disorder, you should see a good GP.  There are specific forms of psychological therapy that you may need to engage with.  Some people also need medications to assist with the process.

For most people though, we can simply allow the recalled feeling of fear stop us from engaging in life.  When we sense fear, the natural reaction is to run or fight.  That is the direct pathway talking in our brain. The lesson from our neurobiology is that we have another choice.  We can let our cerebral cortex do its job, we can think about the situation, and allow our higher functions to downgrade our primitive reactions.

We also need to understand that fear is ok.  It is necessary, in fact.  Without it, we wouldn’t adapt to our surroundings or learn from our mistakes.  We should not avoid fear.  We should not fight fear.  But we should not let fear control us.

Nelson Mandela, a man who experienced great fear but greater hope, sums it up beautifully, and so gets the final word, “Courage is not the absence of fear, but the triumph over it.”

References
[1] Dalgleish, T., The emotional brain. Nat Rev Neurosci, 2004. 5(7): p. 583-9.