title: Axons from restricted regions of the cortex pass through restricted portions of the corpus callosum in adult and neonatal rats.
abstract: It is known that development of the interhemispheric pathway is accompanied by a dramatic reduction in the number of callosal fibers. By injecting neuroanatomical tracers into the cortex of newborn and adult rats, we examined the distribution of fibers within the corpus callosum both before and after this loss takes place. We found that in both newborn and mature rats, axons from restricted regions of the cortex are grouped into relatively tight bundles within the corpus callosum and that the location of these bundles depends upon the region of cortex from which they originate. These results indicate that callosal fibers that are destined to disappear are not distributed diffusely throughout the corpus callosum of the neonate, but rather that they traverse this commissure through the sector that is appropriate for the area of the cortex from which they originate. This finding suggests that loss of axons does not play a significant role in establishing the overall topographic pattern of the fibers within the callosal commissure.
mesh_terms: D000375:Aging; D000818:Animals; D000831:Animals, Newborn / Q000033:anatomy & histology; D001369:Axons / Q000166:cytology*; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000033:anatomy & histology / Q000254:growth & development*; D003337:Corpus Callosum / Q000033:anatomy & histology / Q000254:growth & development*; D006735:Horseradish Peroxidase; D051381:Rats; D013238:Stereotaxic Techniques
chemical_list: D006735:Horseradish Peroxidase