1. BACKGROUND In the early nineteenth century, Franz Gall, a German- born physician and neuroanatomist who studied and worked in Vienna, proposed that specific functions or behaviors are controlled by particular regions of the cerebral cortex. Although Gall extended this proposition to develop the (incorrect) doctrine of phrenology, it was the first account of localization of function in the cerebral cortex. Forty years later Gall's ideas were extended by Paul Pierre Broca, who in 1861 published an account of a patient who could understand language but could not speak. Postmortem examination of the patient's brain showed a lesion in the posterior area of the frontal lobes, an area that has become known as Broca's area. This intriguing finding led to the search for more functionally distinct regions of the cerebral cortex and, in 1870, Fritsch and Hitzig reported that electrically stimulating the pre- central gyrus in the dog resulted in movements of the contralateral limb. Fritsch and Hitzig had found what is now known as the primary motor cortex. Investigation of localized functional regions of the cerebral cortex in- creased at a rapid pace and by the mid-twentieth century it was well established that the cerebral cortex could be divided into discrete regions on the basis of cytoarchitec- tonics (type, density, and layering of cells) and physiolo- gical function. Localization of function in the cerebral cortex is perhaps best demonstrated in the mammalian visual cortex, where in the primate and presumably the human, more than 30 distinct cortical regions associated with the analysis of visual information exist. The localization of function in the cerebral cortex has traditionally relied on techniques such as lesion studies, neuroanatomical tract tracing and single-cell electrophy-