Projection of Fast Afferents to the Cerebral Cortex of Monkey

¹ From the Department of Anatomy, Wayne University College of Medicine, Detroit, Michigan

The projection of fast afferents to the cerebral cortex of the monkey was studied in acute experiments, in which various lesions were made in the cervical cord, and chronic experiments, in which similar lesions were made under aseptic conditions. By stimulating various peripheral nerves and recording evoked potentials from sensory and motor cortex, it was found that section of dorsal funiculi generally causes no significant change in latency or threshold of evoked potentials. The paths still available include the spinothalamic tract contralaterally and an ipsilateral path the nature of which is still uncertain. These additional paths are available for several modalities. As in the cat, muscle afferents do not reach the medulla directly by way of dorsal funiculi. Chronic lesions of these funiculi cause little deficit in animals observed for several weeks or months. Latency of potentials recorded from motor cortex is longer than that of postcentral potentials. The former apparently use different thalamocortical projections. The predominant projection to both motor and sensory cortex is cutaneous.