Cortical Projections of Fast Visceral Afferents in the Cat and Monkey

Abstract

Spinal pathways for cortical projections of splanchnic afferents were studied in cat and monkey, using oscillographic methods. Projections to contra-lateral somatic areas I and II, and ipsilateral II, in the cat were confirmed. The evoked potentials depended upon the activation of fast conducting fibers. Section of dorsal funiculi did not always abolish such potentials. Additional pathways must therefore exist, and it seems likely they are in the ipsilateral lateral funiculus. The fiber spectrum and dorsal column component of the splanchnic in the monkey is strikingly different from the cat. The number of large myelinated fibers is extremely reduced in the monkey. Evoked cortical potentials in the monkey following splanchnic stimulation were not found. This negative result may be due to the small number of large afferents and to the anesthesia. The possible physiological significance of these species differences is briefly discussed, and the fact that splanchnic nerves in man contain numbers of such large afferents is mentioned.