A (Slightly Rambling) Thought Experiment on Bodies and Brains

Within the past month or so, I’ve encountered an astonishing assertion in several places. Not only is the assertion astonishing to me, it’s surprising that individuals whom I know to be intelligent and critical thinkers have offered it. This idea is—to perhaps oversimplify it a bit—that “brains are brains”. That is, absent congenital defect or physical trauma that obliterates part of one’s brain, all normal human brains are roughly equivalent in functionality. I’m going to try to refute this idea in two different ways, because each seems important. They may not appear to be so different to others, however.

I understand the appeal of such thinking to some degree: because we all are configured the same, grossly speaking, it’s tempting to assume that our bodies all function roughly equivalently. And they do, to a large degree: we have the same biological needs that drive much of our behavior—hunger, thirst, oxygen, reproduction, social interaction, mental stimulation. Many of those needs are satisfied by fairly straightforward mechanical processes various organs and organ systems undertake, governed to some degree by the brain’s signals. All of this is ultimately controlled via one’s DNA—the biochemical code that not only directs our construction from zygote to infant to adult, but conducts a lifelong symphony performed by the orchestra of one’s body: genes switch on and off, influencing the type and levels of various vitally important substances in our body (hormones and proteins, for example); and they can mutate, either benignly or malignantly. While it may be somewhat accurate to view the lungs as fairly straightforward, mechanistic respiration devices, I think it is a gross oversimplification to view the brain in the same way.

I don’t mean to suggest that other organs aren’t responsive to one’s environment; they obviously are. I do think, however, that the brain is qualitatively different from them in that it is exquisitely sensitive to environmental information, and it itself changes based on that as well as its own functioning. For optimal development, a brain seems to require levels and varieties of stimulation that other systems do not. (This may be my mistaken idea borne of insufficient knowledge of extant research.) One obvious way it changes was recently revealed in a New Scientist article titled Memories may be stored on your DNA. The entire article is fascinating (and as an aside, supports my assertion here some time ago that brains are regenerated, as other body cells are), but most important for this consideration, it described how a neuron changes over the course of both short-term and long-term memory formation (references and hyperlinks omitted):

Many genes are already coated with methyl groups. When a cell divides, this "cellular memory" is passed on and tells the new cell what type it is – a kidney cell, for example. Miller and Sweatt argue that in neurons, methyl groups also help to control the exact pattern of protein expression needed to maintain the synapses that make up memories.

They started by looking at short-term memories. When caged mice are given a small electric shock, they normally freeze in fear when returned to the cage. However, then injecting them with a drug to inhibit methylation seemed to erase any memory of the shock. The researchers also showed that in untreated mice, gene methylation changed rapidly in the hippocampus region of the brain for an hour following the shock. But a day later, it had returned to normal, suggesting that methylation was involved in creating short-term memories in the hippocampus.

To see whether methylation plays a part in the formation of long-term memories, Miller and Sweatt repeated the experiment, this time looking at the uppermost layers of the brain, called the cortex.

They found that a day after the shock, methyl groups were being removed from a gene called calcineurin and added to another gene. Because the exact pattern of methylation eventually stabilised and then stayed constant for seven days, when the experiment ended, the researchers say the methyl changes may be anchoring the memory of the shock into long-term memory, not just controlling a process involved in memory formation.

Thus, while it may be the case that “all brains are created equal”, they very rapidly diverge and become highly individualized, beginning in infancy.

That said, I don’t think that all brains are created equal. How can it be logical to think that the brain is somehow immune from the kinds of disorders that can be found in other systems? A quick look through metabolic diseases reveals that that vital process can break down at almost every step. Moreover, as is commonly known with lactose intolerance, these genetically-linked problems can wax and wane over the course of a lifetime. This is because the model of one gene (pair, in cases of non sex-linked disorders) controlling one step—and therefore, acting as an on/off switch for one specific disorder—is simplistic in most cases. While one gene or gene pair may be a primary controller, others’ roles can attenuate or exacerbate its expression.

Perform this simple observation: put your hands together, fingers curled into your palms, and observe the pattern of veins on the back of each hand. Are they identical? I would bet not. The same genes instruct their growth and repair/replacement, but even within the global environment of your body, the results are different between the two locations. Thus, even if two individuals had exactly same genes, the chances of their brains developing and maturing identically from infancy to adulthood are vanishingly slim, not only because their experiences and therefore memories will be slightly different, but because those same genes may be expressed differently in the two bodies. This is borne out by observation of identical twins, as well as clones of animals.

Just as genes confer differing physical abilities, they surely must confer differing mental abilities. It may be the case that the delicate balances of neurotransmitters and/or other substances—and other cellular activities that influence neuronal activity—reveal themselves in terms of certain fundamental capabilities, e.g., abstract thought, problem solving, spatial thinking, kinesthetic awareness, or emotional awareness and/or responsiveness. Aren’t these and other “traits” or capabilities the things we look for in those personality tests that identify us as some type or other, or those “intelligence” tests that tell us what kind of learner or thinker we tend to be?

Indeed, I think we acknowledge these fundamental differences in typical brain functioning to some degree when we make our glissando slides from “normal” activity to “disordered” thoughts and behaviors, e.g., from handwashing as good personal hygiene to obsessive urges to wash hands that lead to overwashing and damaged skin. Or, to take a broader example, from shy, geeky person to Asperger’s syndrome. But these observations lead me too far astray from today’s ramble.

So, it seems to me that our brains are in some important ways atypical organs as compared to lungs or livers or hearts. Despite that, brains remain subject to the kinds of malformed genetic blueprints that can lead to problematic organ functioning, just like the rest of our organs. It’s these observations that lead me to reject the idea that all nominally intact human brains function similarly enough to be interchangeable, as pancreases or kidneys can be.

Am I missing something here?