Morphological Relationship Established Through the Habenulo-Interpeduncular System Between the Right and Left Portions of the Frog Brain

Abstract

It is known that the left and right cerebral hemispheres of man are not functionally equivalent. The classification of verbal versus perceptual functions has produced the distinction of the left 'dominant' hemisphere and the right 'minor' hemisphere in man. On these grounds, we might consider the commissures, or at least some of them, as fibre bundles which connect non-homologous structures that topologically occupy the same zone in the two halves of the brain. This concept is strengthened by the observation that the different functional specialisation of the two hemispheres is probably related to their morphological asymmetry. In man the area behind the auditory cortex in the temporal lobe is larger in the left hemisphere than in the right (Geschwind and Levitzky, 1968). On the other hand, the mass of periventricular brain tissue in the posterior part of the hemisphere is greater on the right than on the left, the occipital horn of the lateral ventricle being longer on the left than on the right (McRea et al., 1968).