Interhemispheric connections differ between symmetrical and asymmetrical brain regions.
Coronal sections from the brains of male Wistar rats that underwent corpus-callosectomy in adulthood were stained with Cresyl Violet for Nissl substance or by the Fink-Heimer method for terminal axonal degeneration. Measurements of volumetric asymmetry of neocortical region SM-I were made, and the per cent of terminal degeneration computed. As in previous studies, there was a negative correlation between asymmetry coefficient and total (right plus left) architectonic volume, indicating that symmetrical brain regions are larger than the average of the corresponding regions in asymmetrical brains. It was also found that as volumetric asymmetry increased, the per cent of axonal termination decreased, partly as a result of a decrease in the number of patches of callosal axonal termination. These results are interpreted in the light of what is known about the ontogenesis of callosal connectivity, and mechanisms for the development of architectonic asymmetry in the cerebral cortex are postulated.
Rosen
G D
GD
Dyslexia Research Laboratory, Beth Israel Hospital, Boston, MA 02215.
Sherman
G F
GF
Galaburda
A M
AM
D000818:Animals; D001921:Brain / Q000166:cytology*; D003337:Corpus Callosum / Q000166:cytology*; D007839:Functional Laterality; D008297:Male; D009410:Nerve Degeneration; D051381:Rats; D011919:Rats, Inbred Strains