Hemispheric asymmetry and corpus callosum morphometry: a magnetic resonance imaging study.

Previous post-mortem studies (Aboitiz, F., Scheibel, A.B., Fisher, R.S., Zaidel, E., 1992. Brain Res. 598, 154-161 and Aboitiz, F., Scheibel, A.B., Zaidel, E., 1992. Brain 115, 1521-1541) have shown an inverse association between asymmetry in perisylvian areas and the size of a specific segment, the isthmus, of the corpus callosum (CC) in males. The purpose of this work was to study in vivo the association between hemispheric asymmetry and the total size of the CC in 35 right-handed subjects (16 males, 19 females; mean age 24.9 +/- 3.9). An MRI scan was performed for each subject. The area of the right (RH) and left (LH) hemispheres were measured from images in the sagittal plane and the area of the CC from images in the mid-sagittal plane. The index of hemispheric asymmetry was absolute value((LH - RH)/[(LH + RH)/2]). There was a negative correlation between the absolute value of hemispheric asymmetry and the size of the CC in males (r = -0.55, P = 0.03) but not in females (r = -0.20, P = 0.42). These findings, like those of Aboitiz et al. (Aboitiz, F., Scheibel, A.B., Zaidel, E., 1992. Brain 115, 1521-1541), suggest a sex-dependent decrease in interhemispheric connectivity with increasing hemispheric asymmetry.