Developing Concepts of Lateralization of Cerebral Functions

Abstract

The discovery that certain cerebral functions such as speech had a unilateral representation in the brain followed and was intimately tied to the earlier discovery that motor functions were represented in the contralateral hemisphere. This condition led to the fallacious conclusion that dominance was hemispheric, i.e., that in the right preferent subjects the activity of all areas in the left hemisphere was dominant over the activity of the right hemisphere areas. This article traces the historical sequence of ideas which eventually permitted the discovery of the medullary crossing of the pyramids, the difficulties surrounding the acceptance of unilateral speech representation, the subsequent hemispheric dominance notions, the current neuropathological evidence questioning such ideas and EEG findings including EEG phase analysis data.