Cerebral Asymmetries and Corpus Callosum Morphology

Abstract

The evolution of cerebral asymmetries and their relationship to functional lateralization in the brain are important topics in anthropology, anatomy, biology, and neuropsychology. A brief review of the phylogeny of cerebral asymmetry is appropriate in this context. Evolutionary theory has assumed that functional lateralization in the higher levels of the phylogenetic scale leads to asymmetry in structure. It was believed that the more complex an organism, the more asymmetry in brain structure. In particular, cerebral asymmetries have been assumed to be related to language development in man, since Broca (1865) proposed his notion of cerebral dominance for language. Anthropological considerations led Broca (1861), among others, to believe that the frontal lobes were important for language because of the dramatic increase in their size in humans. When he produced lesion evidence in support of this he also observed that language loss usually occurred with left-sided lesions, establishing the most consistent functional asymmetry in the human brain.