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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