May 03 2011

Categorizing Brain Function

This week on the SGU I will be interviewing Jon Ronson about his latest book, The Psychopath Test, just being released in the US. I am not going to write about the book here (I will do that after the interview, although I have already read a preview copy). Rather, as a prelude to the interview I want to discuss some background thoughts about how we think about brain function in the context of psychology and psychiatry. What I am actually going to give you is my own current synthesis, acknowledging that there is lots of wiggle room for interpretation and opinion, and my own thoughts have been constantly evolving over the years.


It is somewhat of a false dichotomy to think of brain function in terms of hardware and software. That compelling computer analogy tends to break down when you apply it to the brain, because in the brain hardware and software are largely the same thing. Memories are stored in the same neurons that make up the basic structure of the brain, and experiences can alter that structure (to some degree) over time. The brain is neither hardware nor software – it’s wetware.

But it is still useful to think of brain function in terms of long-term structures in the brain – modules and networks that make up the basic functioning of the brain and change slowly (if at all) over time, and short term structures and processes that subsume short-term memory, our immediate experiences, mood, and emotions, and our attention and thoughts. The latter is as close as we get to “software”.

First let’s consider what processes lead to the basic neuroanatomy of the brain – the factors that determine, for example, that the occipital lobe will process visual information, and that it will do so in a very specific way. We can talk about Wernicke’s area in the brain, because everyone seems to have one, it is always in the same place (although sometimes can be on the opposite side) always serves the same function (to process language), and always makes the same connections to other parts of the brain. Yes – there is variation in neuroanatomy, just as there is variation in every biological parameter, but the consistency at this scale is very high.

As we delve into finer and finer details of anatomy, then individual variation becomes greater and greater. While everyone has a Wernicke’s area, some people seem to be born with greater language facility (perhaps “potential” is a better term) than others. What determines this?

It is clear that the ultimate cause is our genes – they contain the instructions for growing a brain. To borrow an analogy from Richard Dawkins (which was pointed out to me by a friend of mine, Daniel Loxton), the genes are not a blue print, but are rather a cook book. In other words – they do not determine where every neuron goes. They determine the rules by which the neurons are laid out, but by following those rules greater complexity emerges. Patterns are repeated and neurons are mapped, to the body and to sensory input. Our sensory cortex, for example, maps itself out to the surface of the body. This is a dynamic process that requires information input, and it is for this reason that the brain can contain much more information than the entire genome, let alone just those genes that code for brain proteins.

In addition to genes there are also epigenetic factors – environmental factors that influence how the genes are expressed. Genes can be turned on and off in various cell populations, and further this is not a binary state – meaning that genes can be turned on to various degrees. A particular gene can be a little active, making a small amount of protein, or can be very active and crank out large amounts of its protein. The environment in the womb, for example, exerts powerful epigenetic influences on gene expression in the developing fetus. This includes the stress of the mother, the diet of the mother, and the levels of various hormones in the blood.

The third factor is developmental. The genes, modified by epigenetic factors, may have a plan for the brain, but that plan still needs to be executed in the developmental process. And that process can go awry, or be interfered with by external factors, like infection, or the presence of a twin.

The combination of genetic, epigenetic, and developmental factors then result in the final structure of the brain. Now it gets really interesting, and increasingly difficult to make categorical statements.


The brain is an organ evolved to interact with the environment, to be adaptive and to learn. That is the whole point of having a brain – to respond to the environment much more quickly than genes themselves can allow (even with epigenetic factors, which do allow for single generation responses to the environment). It is therefore no surprise that after birth (and one can argue even before birth), as the brain grows and matures, it is adapting itself to the environment and responding to all the various inputs it is receiving. Experiences, culture, family life, and other environmental factors all influence brain function.

The never-ending question, however, is to what degree are the functions of the brain determined by hardwiring (shorthand for the genetic, epigenetic, and developmental factors I described above) vs environmental factors. Here is where opinion seems to outweigh evidence. My personal opinion is that both are involved in almost every aspect of brain function, and to various degrees. Some aspects of brain function are dominantly determined by hardwiring. This applies to all the basic functions of the brain, like vision, motor function, wake-sleep cycle, breathing, and the like. Other aspects are perhaps dominantly determined by environment, such as language and culture. And many things are somewhere in the middle.

Most relevant to psychiatry is the question of personality. To what degree are individual personality traits determined by hardwiring vs environmental factors? Here our ability to categorize brain function is stretched to the breaking point. Scientists argued bitterly about where to draw the line around the category of “planet.” They had to deal with only a few variables – size, shape, gravitational influence, the presence of moons, and perhaps a couple of others. And yet what they found was a confusing continuum of objects, and no truly objective way of using the identified variables to come up with an operational definition for “planet” that was not controversial.

Psychologists and psychiatrists have hundreds of variables to consider, that interact with each other in complex ways. Categorization is all but hopeless. However, there still appear to be “islands of stability” – or personality profiles that peak above the noise and can be identified and treated as a real entity. But we can never get away from the complexity.

Let me back up a bit, however, and get back to personality traits. The first challenge is identifying what these traits actually are. Is there really a part of the brain that determines how extroverted vs introverted we are? Is extroversion even a real brain function, or is it the end result of deeper underlying functions? This gets to one of the problems with thinking about human psychology. We generally are identifying three factors: mood, thoughts, and behaviors. We largely rely upon people to tell us how they feel and what they are thinking, and we can observe behavior. We then infer from these three end-results what the underlying personality traits might be. We are like chemists before the periodical table of elements was formulated. We are not sure if we are dealing with the fundamental units of personality (although I think we are in some cases). It is still very much a work in progress.

However, there is another layer of complexity in that mood, thought, and behavior occur within various simultaneous contexts. Movies exploit this all the time – we may see a character behaving in a certain way that seems puzzling, or that makes us jump to certain conclusions about their personality. Only later is the context revealed, and we realize that the character was simply reacting to their situation in a way we might feel is reasonable. The issue of context is critical.

So mood, thought, and behavior are end results of underlying personality tendencies interacting with the environment. The environment not only includes the immediate situation, but also the recent experiences of a person, and even the long term experiences that may have taught them to react in a certain way, their family life, their culture, and any subcultures in which they may be involved. Before any conclusions can be drawn about a person’s personality, we must therefore know a great deal about their individual context.

Another layer of complexity is that individual personality traits, assuming we can even identify them, do not exist in isolation but also interact with each other. Someone who is extroverted and aggressive will behave differently from someone who is extroverted and shy, or extroverted and highly empathic.

The number of variable we are dealing with now are staggering, and the result is chaos (in the mathematical sense).

Conclusion – The Challenge of Psychology/Psychiatry

At this point it should seem like folly to place a label on someone’s psychological condition, and to some extent it is. However, as I said, there are recognizable islands of stability in the chaotic sea of psychology. Some people have a personality trait that is at one or the other extreme end of human variation, and tends to dominate their mood, thought, and behavior. For example, someone may have their anxiety cranked up to maximum, to the point that they are anxious in situations that would not make most people anxious. Their anxiety controls their life, and overshadows other aspects of their personality.

They are still an individual, with many other personality traits and their own complex individual context, and therefore they are different from every other person with anxiety. But it is still meaningful to think of them as a person with an anxiety disorder, and to treat the anxiety to bring it down to a more functional level. The overwhelming complexity of the human brain does not mean we should throw up our hands and abandon all attempts to help people with what can meaningfully be called psychological “disorders”.

But it does mean that we need to proceed with extreme caution. We need to be skeptical of the tentative labels that we use to help guide our thinking about treatment. No person can be reduced to a label – to a single feature about them. People are not “schizophrenics” – they are complex individuals who have a suite of personality tendencies that together fit into a vague and fuzzy, if still recognizable, category we call “schizophrenia.” And this is not just being PC – it reflects the importance of recognizing how we think about brain function at every level, with all of the limitations that are implied.

I had all this in mind when I read The Psychopath Test by Jon Ronson, which details his personal journey to understand just a single psychiatric diagnosis and the quagmire that led him to. I look forward to discussing his book with him this week.

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