Projection of the digit and wrist area of precentral gyrus to the putamen: relation between topography and physiological properties of neurons in the putamen.

The autoradiographic technique was used to examine the projection from the digit and wrist area of the precentral gyrus to the putamen in two macaque monkeys. Motor responses elicited by intracortical microstimulation were mapped to guide selection of the site of injection of isotope. Additionally, an electrophysiological study of the activity of putamen neurons during voluntary movements of the distal arm in an awake monkey was performed prior to the anatomical study in one of the animals. Two major findings resulted from this study. Firstly, the area of representation of the digits and wrist in area 4 gives rise to a substantial projection to the putamen. The distribution of terminals consisted of a simple pattern of clusters at anterior levels of the putamen. At caudal levels in the putamen, the clusters merged into a single diagonal band of label. This basic pattern was found to be virtually identical in the two monkeys. Secondly, the location of neurons in the putamen which were activated during voluntary movements of the distal arm was closely associated with the terminal distribution of fibers from the digit and wrist zone of area 4. These data provide strong evidence to support the idea that the putamen is concerned with motor function of distal muscles of the arm, and that the topographic characteristics of the corticoputamen projection are closely related to the physiological properties of individual neurons in the putamen.