EFFERENT FIBERS OF THE PARIETAL LOBE OF THE CAT (FELIS DOMESTICUS)

Abstract

The left parietal lobes of 14 adult cats were exposed and ablations of the cortex were done using Garol''s map of the sensory cortex as a guide for the limits of the excisions. Complete anatomic studies were done upon 6 of these animals using Busch''s modification of the Marchi method for the myelinated fibers and gallocyanin for studies of cytoarchitecture. The cortical pattern was composed of 6 layers which were similar throughout the parietal lobe save for an increase of depth of the molecular layer posteriorly. No Betz cells characteristic of the motor cortex were seen. The parietal lobe sent association fibers to adjacent homolateral cerebral lobes and commissural fibers by way of the corpus callosum to the contralateral parietal lobe. Parie-tothalmic fibers terminated in the nuclei ventralis postero-lateralis, ventralis posteromedialis, posterior and pulvinar. Parieto-tectal fibers ended in the superior colliculus. Parieto-spinal fibers accompanied the pyramids to the spinal cord in which they were associated with the lateral cortico-spinal tracts of the opposite side where they rapidly ran out in the cervical region. The functional significance of this parietal projection system is reviewed and from this investigation it is believed that the most plausible function is one of a sensitization mechanism for sensory neurones.