The Structure of the Human Brain

Precise studies of the size and shape of the brain have yielded fresh insights into neural development, differences between the sexes and human evolution

John Allen, Joel Bruss, Hanna Damasio

Nineteenth-century phrenologists believed that characteristics such as wit or valor could be determined by feeling a person's skull—an approximation of the size and shape of their brain. As absurd as that notion seems today, it contained a nugget of truth: Brain structure does reflect many influences, including evolution, development and pathology. Using magnetic resonance imaging and computed tomography, neuroanatomists in the emerging field of brain volumetrics are discovering new answers to some old questions: What distinguishes the brains of men and women? Do genes or environment have greater influence on the size of a person's brain? What happened to the hominid brain during the evolution of Homo sapiens? Allen, Bruss and Damasio conclude with the most recent studies from their own lab, which answer the question: What happens to the parts of our brain that we don't use?

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