LAUSR

In the current investigation, we examined the role of different cortical fields in the fronto-parietal reaching and grasping network in awake, behaving macaque monkeys. This network is greatly expanded in primates compared to other mammals and co-evolved with glabrous hands with opposable thumbs, and the extraordinary dexterous behaviors employed by a number of primates, including humans. To do this we reversibly deactivated the primary motor area (M1), anterior parietal area 2, and posterior parietal areas 5L and 7b individually while monkeys were performing two types of reaching and grasping tasks. Reversible deactivation was accomplished using small microfluidic thermal regulators abutting specifically targeted cortical areas. Placement of these devises in the different cortical fields was confirmed post hoc in histologically processed tissue. Our results indicate that the different areas examined form a complex network of motor control that is overlapping, but several consistent themes emerged which suggest the independent roles that motor cortex, area 2, area 7b and area 5L play in the motor planning and execution of reaching and grasping movements. Area 5L is involved in the early stages and area 7b the later stages of a reaching and grasping movement, motor cortex is involved in all aspects of the execution of the movement, and area 2 provides proprioceptive feedback throughout the movement. We discuss our results in the context of previous studies that explored the frontoparietal network, the overlapping (but also independent) function of different nodes of this network, and the rapid compensatory plasticity of this network.