Motor Cortical Encoding of Hand Orientation in a 3-D Reach-to-grasp Task

The activity of 979 motor cortical cells was recorded in a monkey trained to reach and grasp one of two targets oriented at various angles. 568 cells were found to be task-related and further classified. Among them, 24% correlated only with target orientations which determined hand orientation, 18% correlated only with target location (movement direction), 24% correlated with both target orientations and locations. Thus, hand orientation is an important control parameter during reach-to-grasp task. The data showed that in the motor cortex a portion of neurons could code hand orientation independent of movement direction. At the same time, cells encoding hand orientations and cells encoding movement directions coexist in the same region of the motor cortex, which indicates there probably exists a common pathway in M1 that controls both parameters