Despite the broad philosophical thrust of "Neuronal Man," Changeux's own contributions to neurobiology have been at the cellular and molecular level. His laboratory of molecular neurobiology at the Institut Pasteur in Paris has extended the scope of that intellectual center beyond the traditional "Pasteurien" subjects--those closely related to microbiology. But true to his training and his earlier accomplishments, Changeux frames his understanding of the brain in terms of the action of genes. In doing so, he must confront a major paradox: the relative simplicity of the genetic plans compared to the complexity of the brain. How can a mere 100,000 or so genes specify the connections among the tens of billions of neurons in the human brain? The last third of "Neuronal Man" explores how this may happen.
The key to the brain's complexity, Changeux claims, derives from the same selective principle as the diversity of species. Genetic plans allow the initial development of many neural connections, of which only a subset persists. Taking a page from Darwin, Changeux argues that neural connections are subject to selection based on experience. Useless networks thus disappear, while networks that encode mental objects corresponding to reality are stabilized.
"Neuronal Man," based on Changeux's lectures at the College de France, is an ambitious book, providing provocative instruction for scientists and nonscientists alike. The French edition, enthusiastically received by the French press and public, won the Broquette-Gonin Literary Award from the Academie Francaise. Some of the book's arguments occasionally seem contrived, but most of the time it appears that Changeux is looking where others have looked and is seeing what others have not seen.