Small-diameter nonmyelinated axons in the primate corpus callosum.
The splenium of the corpus callosum of a primate (Macaca mulatta), examined with the electron microscope, was found to contain both myelinated and nonmyelinated axons. The majority of nonmyelinated axons had diameters of less tha 0.25 micron. On the basis of this diameter distribution, it is expected that many callosal axons conduct impulses at velocities of less than 1 m/s and that interhemispheric conduction times for some callosal axons are at least 30 ms and possibly much longer.
D000818:Animals; D001369:Axons / Q000648:ultrastructure*; D003337:Corpus Callosum / Q000033:anatomy & histology*; D000882:Haplorhini; D008252:Macaca fascicularis; D008253:Macaca mulatta; D009413:Nerve Fibers, Myelinated / Q000648:ultrastructure