Gray Matter
The New Science of Mind
By ERIC R. KANDEL
Published: September 6, 2013
THESE days it is easy to get irritated with the exaggerated interpretations of brain imaging — for example, that a single fMRI scan can reveal our innermost feelings — and with inflated claims about our understanding of the biological basis of our higher mental processes.
Olimpia Zagnoli
Such irritation has led a number of thoughtful people to declare that we can never achieve a truly sophisticated understanding of the biological foundation of complex mental activity.
In fact, recent newspaper articles have argued that psychiatry is a “semi-science” whose practitioners cannot base their treatment of mental disorders on the same empirical evidence as physicians who treat disorders of the body can. The problem for many people is that we cannot point to the underlying biological bases of most psychiatric disorders. In fact, we are nowhere near understanding them as well as we understand disorders of the liver or the heart.
But this is starting to change.
Consider the biology of depression. We are beginning to discern the outlines of a complex neural circuit that becomes disordered in depressive illnesses. Helen Mayberg, at Emory University, and other scientists used brain-scanning techniques to identify several components of this circuit, two of which are particularly important.
One is Area 25 (the subcallosal cingulate region), which mediates our unconscious and motor responses to emotional stress; the other is the right anterior insula, a region where self-awareness and interpersonal experience come together.
These two regions connect to the hypothalamus, which plays a role in basic functions like sleep, appetite and libido, and to three other important regions of the brain: the amygdala, which evaluates emotional salience; the hippocampus, which is concerned with memory; and the prefrontal cortex, which is the seat of executive function and self-esteem. All of these regions can be disturbed in depressive illnesses.
In a recent study of people with depression, Professor Mayberg gave each person one of two types of treatment: cognitive behavioral therapy, a form of psychotherapy that trains people to view their feelings in more positive terms, or an antidepressant medication. She found that people who started with below-average baseline activity in the right anterior insula responded well to cognitive behavioral therapy, but not to the antidepressant. People with above-average activity responded to the antidepressant, but not to cognitive behavioral therapy. Thus, Professor Mayberg found that she could predict a depressed person’s response to specific treatments from the baseline activity in the right anterior insula.
These results show us four very important things about the biology of mental disorders. First, the neural circuits disturbed by psychiatric disorders are likely to be very complex.
Second, we can identify specific, measurable markers of a mental disorder, and those biomarkers can predict the outcome of two different treatments: psychotherapy and medication.
Third, psychotherapy is a biological treatment, a brain therapy. It produces lasting, detectable physical changes in our brain, much as learning does.
And fourth, the effects of psychotherapy can be studied empirically. Aaron Beck, who pioneered the use of cognitive behavioral therapy, long insisted that psychotherapy has an empirical basis, that it is a science. Other forms of psychotherapy have been slower to move in this direction, in part because a number of psychotherapists believed that human behavior is too difficult to study in scientific terms.
ANY discussion of the biological basis of psychiatric disorders must include genetics. And, indeed, we are beginning to fit new pieces into the puzzle of how genetic mutations influence brain development.
Most mutations produce small differences in our genes, but scientists have recently discovered that some mutations give rise to structural differences in our chromosomes. Such differences are known as copy number variations.
People with copy number variations may be missing a small piece of DNA from a chromosome, or they may have an extra piece of that DNA.
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