[Cerebral laterality and interhemispheric connections: neurobiologic aspects]

Abstract

This review summarizes evidence favouring two kinds of anatomical correlates of cerebral lateralization. The first, cortical asymmetries, is widely accepted today. It is now known that there are significant asymmetries in brain regions corresponding to the so-called "language areas". These asymmetries are present at the level of gross anatomy (i.e., length of the Sylvian fissure), and at a more detailed cytoarchitectonic level. Furthermore, it is known that, in different subjects, the extent of the asymmetries correlates well with the degree of functional lateralization. The second anatomical variable is commisural connectivity. The corpus callosum has been postulated as pivotal in the workings of a lateralized brain. There have been controversial reports suggesting a correlation between callosal structure and parameters related to brain lateralization, such as sex and handedness. Together with analysing these results, this review considers some aspects of the fine structure and development of the corpus callosum. These considerations lead to the proposal of specific hypotheses about the relation between brain lateralization and commisural connectivity.