The commissural neurons of the inferior colliculus of the rat

During systematic observation of the cellular subnuclei of the inferior colliculus of adult rats, it was noted that in the zone of the intercollicular commissure, numerous neuronal perikaria appear intermingled between the commissural fibers. The neurons were studied using Golgi and TEM methods and classified according to their dendritic pattern in the isodendritic (15%), allodendritic (19%) and intermediate forms (66%) of neurons. A fourth neuronal group, situated between the commissure and the upper periventricular zone, is also in relation with the commissural fibers. The constancy of these neurons and their frequently axodendritic and axosomatic synapses suggest that they play an important role in the whole function of the commissure which, at present, is not well understood in spite of the number and distinct origin of their afferents.