Kandel was awarded a 2000 Nobel Prize in Medicine or Physiology for his discovery of molecular processes that underlie learning and memory. In addition to running laboratories at N.Y.U. and then Columbia, he has co-written successive editions of the massive and widely used textbook “Principles of Neural Science,” a testament to the same encyclopedic knowledge that is on display in this book. Kandel’s well-constructed narrative smoothly blends historical perspective and first-person accounts with explanations of recent experiments. In a chapter on dementia, for instance, Kandel introduces us to the classic brain pathology studies of Alois Alzheimer (a close colleague of Emil Kraepelin); he tells the celebrated story of patient H.M., whose 1953 brain surgery destroyed his capacity to form new declarative memories; and he guides us through some of his own research on learning in invertebrates and animal models of Alzheimer’s disease. In another chapter, on gender identity, Kandel nicely juxtaposes autobiographical accounts from the late Ben Barres, a prominent neuroscientist who began his life as Barbara, against genetic studies of sexual dimorphisms in mice and humans.

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Kandel is particularly focused on the importance of genetics. Here the author again parallels Kraepelin, who stressed the contribution of heritable “degeneracy” to mental disorders. Kandel credits advances in human genetics and genetic models of disease in animals in large part for our modern appreciation of the brain’s role in mental illness. Although he discusses a variety of basic science approaches, he gives pride of place to analyses involving genes and their associated molecules. Kandel’s enthusiasm for genetics reflects the current priorities of many psychiatric researchers, but it also drives him to occasional exaggerations. His exuberant verdict, that “decoding the human genome has shown us how genes dictate the organization of the brain and how changes in genes influence disorders,” is extraordinarily premature.

The sober truth, some of which emerges elsewhere in the book, is that the relationships between genes and most psychiatric diseases are still far from clear. The majority of implicated genes are only weakly correlated with disease. The world’s economically costliest mental illness, major depressive disorder, has yet to be tied convincingly to any genes. Even where a gene seems to influence brain cell biology in defined ways — as with the remarkable schizophrenia-related C4 gene Kandel features — the connection between cellular hallmarks and high-level psychiatric symptoms remains mysterious. It is notoriously difficult to find relevant animal models to help make this connection (psychotic mice are hard to spot), which means the more arduous research of humans continues. And while genetic techniques may be an excellent bet for psychiatric science, whether there will be payoffs in the clinic is far from certain.

Apart from potential medical benefits, however, Kandel believes that biological studies of the mind “offer the possibility of a new humanism, one that merges the sciences, which are concerned with the natural world, and the humanities, which are concerned with the meaning of human experience.” Neurobiology may indeed be well poised to promote this kind of synthesis. Kandel himself bridges science and humanities in a chapter on the link between mental illness and artistic creativity. He also tries to reconcile Kraepelin-style biologism with more humanistically oriented psychotherapy, correctly assailing the false dichotomy between these two approaches, which in practice both act on the brain.