Organization of motor and somatosensory neocortex in the albino rat

Abstract

The extent and organization of motor (MsI) and somatosensory (SmI) cortex in the rat were investigated using intracortical stimulation with semi-microelectrodes and single- or multiple-unit recording techniques. Two maps of MsI were presented, one based on stimulation with 25-msec bursts of a 1-kHz sinusoidal current, the other based on 250-msec bursts of a 300-Hz stimulus. The first occupied a relatively small region of anterior cortex that was confined to the dorsal surface of the hemisphere and did not reach the frontal pole. The motor area delineated with the 300-Hz stimulus was larger, occupying a significant portion of the anterolateral surface and most of the frontal pole. Movements of the eye and eyelid were elicited from a long thin strip of cortex lying near the midline. The vibrissae were represented in another long strip adjacent to the eye-eyelid region. The delineation of SmI was in good agreement with earlier descriptions, but the hindlimb and forelimb areas overlapped their respective motor areas. The overlap was essentially complete for the hindlimb, but only partial for the forelimb.