Sex differences in corpus callosum size: relationship to age and intracranial size

This quantitative MRI study reports measurement of corpus callosum area tak en from midsagittal brain images in 51 healthy men and 41 healthy women, sp anning the adult age range (22 to 71 years). Men had larger brains acid cor pora callosa than women, but callosal size did not correlate with age in ei ther sex. Intracranial (i.e.) volume (ICV) and midsagittal i.c. area (ICA) of brain were used in covariate, regression, and ratio analyses to determin e whether sex differences in the corpus callosum endured with statistical a djustment fur sex differences in maximally attained brain size. With the ex ception of one ratio measure, the different statistical adjustments for the contribution of sex differences in brain size to corpus callosum size all indicated that men had larger corpora callosa than women for their brain si ze. A subsample of men and women selected to be matched on i.c. volume and age confirmed this statistical observation. Sexual dimorphism in the corpus callosum is not a simple artifact of sex differences in brain size and may reflect differences in connectivity necessitated by differences in brain s ize. (C) 2001 Elsevier Science Inc. All rights reserved.