When I first received this book, I was seized by the impulse to return it to the editor, because I had no special expertise in the neurosciences. After musing for a few minutes, I felt a mild degree of bravado that was manifested in the attitude, Why not review it and, at the same time, learn something about a subject that has an important future? Furthermore, the subtitle implies that the book deals with vexing and puzzling questions about mind-body connections and nature-nurture controversies.

This decision was most fortunate for me and fulfilled my wildest expectations. Instead of laboriously struggling to learn about neurobiology, I found myself fairly effortlessly assimilating information because 1) the author is able to present his material in the context of interpersonal relationships in general and the treatment dyad in particular, and 2) the author is a master of lucidity, avoids pedantry, and succeeds in making his data clinically useful.

Dr. Siegel apparently has well-functioning right and left hemispheres, which accounts for the book’s facile readability in spite of the enormous amount of information he presents and his scholarly and expansive survey of the literature. He stresses an operational definition of the brain that involves processing of information and high levels of energy.

It is impossible in the limited space of this review to discuss the contents of this book thoroughly. The brain has 100 billion neurons, so the complexities involved are enormous. I can only refer to some highlights.

The author focuses on development and points out that at first there are many neurons but relatively few synapses. The latter develop in the context of experiences with caregivers, and that is why this book is a treatise on interpersonal neurobiology. Everything that happens in the brain is related to experience.

For example, if there are inadequate stimulating and nurturing relationships, some neurons undergo what is called pruning. They fail to develop synapses, clusters, and circuits that will be related to adaptation and behavior. The brain continues to develop well into adolescence and young adulthood; therefore, it is a plastic structure that can be influenced anatomically and functionally by traumatic or salubrious experiences.

Dr. Siegel stresses Hebb’s axiom that neurons that fire together link together, meaning that neural circuits and patterns are constructed involving emotion, memory, representations, states of mind, self-regulation, interpersonal connection, and integration. These subjects are briefly discussed in the introductory chapter and then become the subjects of separate chapters. The chapters on self-regulation and interpersonal connection are especially relevant to psychotherapists who treat patients whose psychopathology has disrupted their emotional development.

The brain is asymmetric, and the left and right hemispheres, although they functionally overlap, emphasize different processes. The right brain operates in an analogical fashion and concentrates on internal attention and action, whereas the left brain is linear and externally directed. Different forms of psychopathology involve one hemisphere more than the other; depression, for example, is associated with left brain impairment.

By stressing multiple causality, this book should finally lay to rest theories that create a gap between mind and body. Inasmuch as it details specific connections among anatomy, physiology, and experience, it also has treatment implications that do not create dichotomies like psychopharmacology versus psychotherapy. The brain and the environment are constantly interacting, and, as Dr. Siegel implies, the clinician and the scientist represent different facets of an approach devoted to the acquisition of knowledge and the healing process.