Wisdom part IV: searching for wisdom, neurochemicals?
Neil DeGrasse Tyson says (it’s early in the video) that people get all worked-up about thinking that our brain is ‘all we are’. He says that is a good start, but sort of like saying that elbows are all we are. But why get worked-up? If our brain is all we are, that is pretty damn incredible.
According to a paper by Dr Ahmad Abu-Akel, the ‘theory of mind’ is the ability to represent one’s own or another’s mental states such as intentions, beliefs, wants, and knowledge. This is a definition of consciousness, and as far as we really know, it is a uniquely human phenomenon. Though we are always looking for ToM evidence in animals, in fact this paper calls theory of mind a killjoy: “Yet in the contemporary study of animal cognition, demonstrations that complex human-like behavior arises from simple mechanisms rather than from ‘higher’ processes, such as insight or theory of mind, are often seen as uninteresting and ‘killjoy’, almost a denial of mental continuity between other species and humans. At the same time, however, research elsewhere in psychology increasingly reveals an unexpected role in human behavior for simple, unconscious and sometimes irrational processes shared by other animals. Greater appreciation of such mechanisms in nonhuman species would contribute to a deeper, more truly comparative psychology.”
Patients with disorders affecting the ability of the mind are currently our best window into how consciousness and in the context of this discussion, wisdom, works. At this point it seems easier to study what wisdom is not than to find out what wisdom is.
It seems that neurochemicals might be key to a balanced and healthy mind. It may be that all the memories, worries, personality quirks, language, feelings and every other complex piece that makes up our consciousness, boils down to chemistry.
Serotonin, dopamine, acetylcholine, oxytocin, cannabinoids, and other neurotransmitters are chemicals that our brain uses to relay information between neurons. When one neuron receives an electrical signal that needs to be passed on to the next neuron, the channel proteins studding the surface of the cell open and close, regulating the flow of ions across the membrane and providing the basic signal of the nervous system—the action potential. When the action potential hits the membrane near the synapse, neurotransmitter is released. The molecules diffuse across the synapse and may bind to receptor proteins in the cell membrane of the next neuron.
Different parts of the brain can have different combinations of receptors, so that when the brain is washed with one chemical, activity in a specific part of the brain might increase or decrease. It is a chemical and electrical dance that somehow sums up into a mind. The dance is delicate and any imbalance can result in impairment.
For example, dopamine and serotonin are commonly thought to affect performance in cognitive tasks that are dependent on our large prefrontal cortex. Schizophrenia is linked with dopamine abnormalities, and an inability to breakdown serotonin might result in aggressive and impulsive behavior. High serotonin and low oxytocin levels are also linked to autism. Dopamine is considered to have a central, integrative role in the control of cognitive as well as motor processes. As with much progress in brain research, mental deficits help scientists understand this system. A demyelization of dopamine-receptor neurons in the motor cortex results in Parkinson’s disease, in which initiating motion is difficult. Studies in rhesus monkeys indicate that extraversion, defined as social dominance, might have something to do with dopamine-receptors in the striatum. Serotonin levels are also linked with depression, hence the prosciption of serotonin-uptake inhibitors (SIs) to treat this disease. Check out Scicuious’s excellent posts on the serotonin system and depression.
But everything depends on everything else. Our brain does not do one thing at a time and the picture is not as simple as an excess in A causes behavior B. As Sci explains in the depression post I linked to, our evidence for these chemicals involvment with disease is often sketchy and incomplete. So we continue to treat depression with drugs related to serotonin because it seems to work, not because we know why it works.
Similar story in scizophrenia. It appears that serotonin has a modulatory effect on dopamine release, and as a result, psychopharmacological studies report better results in patients treated with medicines that bind to serotonin and dopamine receptors than medicines that block dopamine receptors alone. So that is the medicine we use.
Complexity confounds, but we still strive
It seems like a herculean task to discover the neurobiological basis of wisdom. Neurobiologists are piecing together the puzzle of how the mind works, but at this point it is like we are blind and some of the pieces are missing. When a piece fits, we can feel that it clicks into place just right, but discovering the whole picture may take a while. This is science, where you can say for sure that the answer is not A, but you can never say for sure if the answer is B. Science only lets you say that B has not been disproved, yet. As someone who grew up in a science-minded household, I’m pretty good with that uncertainty, but many people find it unnerving and as a result distrust ‘science’ as some sort of monolithic institution.
There are people who think that science has pretty much figured everything out. We’ve decoded the human genome, harnessed nuclear energy, discovered evolution, all we need is to do is to cure cancer and maybe fix this global climate change issue, right? It does seem like science has progressed so incredibly in the last century that we can’t keep going at this speed, but that is setting down the book just as the story gets interesting.
Understanding human consciousness and unlocking a mechanism for wisdom may not be around the corner, but science is making fascinating progress. Future neurologists may look back on the beginning of the 21st century as the groundwork for understanding consciousness. We may be in a time, that for neurobiology, is akin to molecular biology just before Waston and Crick elucidated the structure of DNA.
Some papers about neurochemistry
Arenett, JJ (1992). Reckless behavior in adolescence: A developmental perspective. Developmental Review 12:339-373.
Berlin HA, Rolls ET, Kischka U, (2004). Impulsivity, time perception, emotion and reinforcement sensitivity in patients with orbitofrontal cortex lesions. Brain 127(pt5):1108-1126.
Scoville, WB and Milner, B (1957). Loss of recent memory after bilateral hippocampal lesions. Journal of Neurology, Neurosurgery and Psychiatry 20:11-21.
Abu-Akel A (2003). The neurochemical hypothesis of ‘theory of mind’. Med Hypotheses 34(6)1211-1220.
Reeves SJ, Mehta MA, Montgomery AJ, Amiras D, Egerton A, Howard RJ, Grasby PM, (2007). Striatal dopamine (D2) receptor availability predicts socially desirable responding. Neuroimage 34(4):1782-1789.
Bachener-Melman R, Gritsenko I, Nemanov L, Zohar AH, Dina C, Ebstein RP, (2005). Dopaminergic polymorphisms associated with self-report measures of human altruism: a fresh phenotype for the dopamine D4 receptor. Mol Psychiatry 10(4):333-335.
Jacob S, Brune CW, Carter CS, Leventhal BL, Lord C, Cook EH Jr. (2007). Association of the oxytocin receptor gene (OXTR) in Caucasian children and adolescents with autism. Neurosci Lett. 417(1):6-9.
Meyer-Lindenberg A, Buckholtz JW, Kolachana B, Hariri A, Pezawas L, Blasi G, Wabnitz A, Honea R, Verchinski B, Callicott JH, Egan M, Mattay V, Weinberger DR, (2006). Neural mechanisms of genetic risk for impulsivity and violence in humans. Proc Natl Acad Sci U S A, 103(16):6269-6274.
Riling J, Gutman D, Zeh T, Pagnoni G, Berns G, Kilts C, (2002). A neural basis for social cooperation. Neuron 35(2):395-405.
Schultz W, Dayan P, Montague PR, (1997). A neural substrate of prediction and reward. Science 275:1593-1599.