title: A comparative MRI study of the relationship between neuroanatomical asymmetry and interhemispheric connectivity in primates: implication for the evolution of functional asymmetries.
abstract: The authors tested the theory that hemispheric specialization evolved as a consequence of reduced interhemispheric connectivity by examining whether neuroanatomical asymmetries were associated with variation in the ratio of corpus callosum size to brain volume (CC:VOL) and to neocortical surface area (CC:NEO) in human and nonhuman primates. Magnetic resonance images were collected in a sample of 45 primates including 8 New World monkeys, 10 Old World monkeys, 4 lesser apes, 17 great apes, and 6 humans. CC:VOL and CC:NEO were determined and correlated with measures of brain asymmetry. The results indicate that brain asymmetry significantly predicted CC:VOL and CC:NEO. Subsequent analyses revealed that species variation in functional asymmetries in the form of handedness are also inversely related to CC:NEO. Taken together, these results support the hypothesis that leftward brain asymmetries may have evolved as a consequence of reduced interhemispheric connectivity.
authors.affiliation: Department of Psychology, Berry College, USA. whopkins@berry.edu
authors.forename: W D
authors.initials: WD
authors.lastname: Hopkins
authors.forename: J K
authors.initials: JK
authors.lastname: Rilling
mesh_terms: D000328:Adult; D000818:Animals; D005075:Biological Evolution; D002508:Cephalometry; D003337:Corpus Callosum / Q000033:anatomy & histology*; D004292:Dominance, Cerebral / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D019579:Neocortex / Q000033:anatomy & histology; D011323:Primates / Q000033:anatomy & histology*; D013045:Species Specificity