On the relations between the direction of two-dimensional arm movements and cell discharge in primate motor cortex

The activity of single cells in the motor cortex was recorded while monkeys made arm movements in eight directions (at 45 degrees intervals) in a two-dimensional apparatus. These movements started from the same point and were of the same amplitude. The activity of 606 cells related to proximal arm movements was examined in the task; 323 of the 606 cells were active in that task and were studied in detail. The frequency of discharge of 241 of the 323 cells (74.6%) varied in an orderly fashion with the direction of movement.