SEXUAL DIMORPHISM OF THE HUMAN CORPUS-CALLOSUM FROM 3 INDEPENDENT SAMPLES - RELATIVE SIZE OF THE CORPUS-CALLOSUM

Three independent autopsy samples of brains without apparent neuropath ology were studied to ascertain whether there was sexual dimorphism in the human corpus callosum (CC). Using planimetric measurements on mid sagittal brain sections, several morphometric features of the CC were studied: total callosal area, maximum dorsoventral splenial width, the posterior one fifth of the total area of the CC (mostly splenium), an d brain weight. Ratio data correcting for brain size were also studied . In all samples, absolute brain size was larger in males, and signifi cantly so. Measurements of splenial dorsoventral width were higher in females than males, but not significantly, except in the Australian sa mple. Total callosal area was absolutely higher in the Australian fema le sample than in males, and almost equal in the two American samples, without statistically significant differences. The posterior one-fift h area (splenium) was larger for females in each of the samples. The v ariables which were corrected for brain size were usually significantl y larger in females, although this pattern varied in each sample. The statistical pattern of sexual dimorphism for the human CC differs from that found in most other neural structures, such as the amygdaloid nu cleus, cerebellum, hippocampus, and thalamus. The absolute sizes of th ese structures are always significantly larger in males. When correcte d for brain size, the relative sizes are not significantly larger. The CC is the only structure to show a larger set of relative measures in females. (C) 1993 Wiley-Liss, Inc.