Diffusion of electrical current in the experiments of Fritsch and Hitzig and Ferrier failed to negate their conclusion of the existence of cerebral motor centers.

This paper explores the implications of an early criticism of the stimulation studies of Fritsch and Hitzig and Ferrier for localized brain functions. Fritsch and Hitzig and Ferrier concluded that motor centers reside in the cortices of the hemispheres. Their studies were replicated, but their conclusions were not generally accepted initially. The most salient, laboratory-based criticism was that the electrical current used for stimulation diffused well beyond the cortex making their conclusion of cerebral motor centers unacceptable. The diffusion argument was essentially a French suggestion. Ferrier's and American research and interpretations provided data and arguments against it.