Movement of facial muscles following intra-cortical microstimulation (ICMS) along the lateral branch of the posterior bank of the ansate sulcus, areas 5a and 5b, in the cat.

The lateral branch of the posterior bank of the ansate sulcus within the parietal cortex, areas 5a and 5b, was mapped using intracortical microstimulation (ICMS). Motor effective sites for contraction of facial muscles were identified using ICMS currents of less than 30 microA. Of the 177 effective sites, 78% were activated with threshold currents of less than 20 microA, and of these, 33% responded to stimulus strengths of less than 10 microA. Since neurons in this portion of the ansate region send projections to the face region of motor cortex, area 4 gamma, the possibility existed that the motor effects might be mediated through area 4 gamma. To examine this possibility we ablated both the anterior sigmoid gyrus (ASG) and the second somatosensory cortex, SII, including area 2pri, a region shown to contain a low threshold motor component, and report that the motor effect recorded from the ansate region is independent of both the ASG and area 2pri.