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Joseph LeDoux
SYNAPTIC SELF
How Our Brains Become Who We Are
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Book review by Anthony Campbell. Copyright © Anthony Campbell (2004).
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Joseph LeDoux is a neuroscientist best known for his research on
emotion, which he described for a general audience in his 1998 book The
Emotional Brain. The present book is partly an update but, as its title
indicates, it focuses more particularly on the role of synapses. These
are the small spaces between neurons which determine how conduction of
nerve impulses occurs within the brain and therefore, ultimately, how
the brain itself functions. The scope of the book is also wider and more
ambitious than that of the earlier work.
LeDoux certainly could not be accused of insulting his reader's
intelligence. His new book goes into quite a lot of detail about
synapses and how they work at a molecular level, and it is necessary to
keep alert and concentrate to take it all in. The reward for doing this
is to be treated to an up-to-date view of an im****tant area of brain
research, and therefore to an insight into current thinking about what
makes us who we are.
Scientific writing about emotion encounters a linguistic problem at the
outset, because the ordinary usage does not easily translate into a
scientific context. In common parlance, "emotions" are more or less
synonymous with "feelings": fear, anger, ***ual desire and so on could
be described as emotions. But these are essentially human experiences,
and we rely largely on people's verbal descriptions of their feelings to
know if they are having them. Much of the experimental work in
neurology, however, is carried out on animals, and we cannot know what,
if anything, they feel. LeDoux discusses this im****tant subject on pp.
204 and following, and reaches this conclusion.
So my approach has been to discuss emotions (feelings) only with
respect to humans, and to restrict myself to the notion of emotional
processing when I talk about creatures other than humans. In this
way, I avoid the construction of a theory that can never be proven,
but at the expense of having one that may be incomplete. I'm
comfortable with this approach, though others prefer the
alternative.
A little further down the same page, he says that "emotion can be
defined as the process by which the brain determines or computes the
value of a stimulus." So I think we can take it that he uses "emotions"
to refer to brain events that can be studied objectively, and "feelings"
to refer to subjective phenomena that are only available to
introspection. It might have been helpful if he had provided a glossary
to define his terminology more succinctly, because, as it is, one has to
thumb back and forth a good deal to ensure one has grasped his meaning.
There is a widespread notion in popular writings on the brain that
emotion, however defined, depends on an area called the limbic system,
and even scientific texts quite often echo this. LeDoux has an excellent
section on the subject, in which he points out the deficiencies in the
limbic system theory, which he regards as "an off-the-shelf explanation
of how the brain works, one grounded in tradition rather than in facts.
Deference to the concept is inhibiting creative thought about how mental
life is mediated by the brain." In fact, even the existence of the
limbic system as an entity is open to question, and there is little
agreement about which parts of the brain are supposed to form part of
it.
In any case, the most im****tant component of the alleged limbic system,
the hippocampus, is responsible for memory rather than emotion, and much
of the book is about memory. I was particularly interested in the
discussion of long-term potentiation, which many believe is an im****tant
part of the memory mechanism. This is a synaptic phenomenon, and LeDoux
finds that the synaptic basis of memory seems to be common to a wide
range of species across the spectrum of evolution. He is also good on
the different types of memory (explicit, implicit, working) and on how
these come together to constitute the self.
Another area where popular thinking about the brain needs to be updated
relates to the notion of "reward centres". Research on rats in the early
1950s led to the claim that there are "pleasure centres" in the brain
and that stimulating these could be the basis of addiction. LeDoux
teases out the neurological basis for such claims, and shows that the
whole subject is, as might be expected, vastly more complicated than the
initial re****ts implied. This is just one of the many places in which he
looks beneath the obvious to reveal some of the complexity beneath.
What happens in the brain when things go wrong? There is a widespread
notion that much mental disorder is due to "chemical imbalance" in the
brain. LeDoux refers to this idea, disparagingly, as the "soup model".
It is synaptic changes that really matter, he insists; we need a circuit
point of view to understand psychiatric disorders. He discusses
schizophrenia, depression, and anxiety disorders in this context. Some
will no doubt find this to be an excessively mechanistic approach, but
perhaps they will be reassured by his view that our thoughts can
actually modify the way our synapses work.
The downward mobility of thought provides a powerful means by which
parallel plasticity in neural systems is coordinated... With
thoughts empowered in this way, we can begin to see how the way we
think about ourselves can have powerful influences on the way we
are, and who we become. One's self-image is self-perpetuating."
This is a rich book which contains a vast amount of information. What I
particularly like about LeDoux's writing is his open-mindedness. He
presents a vivid picture of work in progress; he defends his own views,
naturally, but he does not fudge the uncertainties and he acknowledges
the existence of other ideas. As a result, the reader gets a genuine
impression of scientific thinking at work in this most exciting and
im****tant of research areas.
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%T Synaptic Self
%S How our brains become who we are
%A Joseph LeDoux
%I Penguin Books
%C London
%D 2003
%G ISBN 0-14-20.0178-3
%P x + 406 pp
%K brain and mind
%O paperback edition
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