The Involvement of Premotor Cortex in Executing Reach to Grasp Movements

Reaching to grasp is an ethologically relevant primate behavior supported by a large network of cortical areas. One classical hypothesis concerning the organization of this network posited that information about reaching and grasping is processed along separate, independent pathways that are temporally coordinated via a central clocking mechanism. According to this hypothesis, known as the dual channels hypothesis, the dorsal premotor cortex (PMd) should be exclusively involved with reaching, while the ventral premotor cortex (PMv) should be exclusively involved in grasping. As a corollary of this hypothesis, the premotor cortex and primary motor cortex should be hierarchically organized. Here, we used multi-electrode arrays to record from both PMd and PMv simultaneously while animal subjects engaged in a reach-to-grasp task. We then developed encoding models that predicted the activity of neurons in these areas based on various kinematic features. We found that the kinematics of both reaching and grasping were predictive of activity in both PMd and PMv. Additionally, we examined the spatio-temporal dynamics of attenuation in the beta frequency range (15-30 Hz) of the local field potential in both areas. We found that beta attenuation propagated spatially across the cortical surface in PMd in a similar fashion to beta attenuation in MI. Collectively, these results are inconsistent with the expectations of the dual channels hypothesis, and instead, imply a more direct role of premotor cortex in movement execution.