Neuronal activity reflecting progression of trials in the pre-supplementary motor area of Macaque monkey: an expression of neuronal flexibility.

AbstractWe studied the activity of single neurons in the pre-supplementary motor area(pre-SMA) of macaque monkeys as they performed two visuomotor tasks, called thevisual fixation task and the visual fixation-blink task. Both tasks involved asequence of three visual stimuli, red followed by yellow and green. The tasksdiffered in that the latter one had a gap within the period of the red stimulus,called a "blink". The tasks were performed in two modes, one of which includedmovements of both the arm and eye and the other of which involved only eyemovements. In the arm-eye mode, the monkeys had to press a bar and fixate the redstimulus that appeared after bar press. To receive a reward, both the bar press andvisual fixation had to be maintained until the green stimulus triggered bar release.In the eye mode, bar press and bar release were eliminated from the task. Of the 42neurons active during the visual fixation task, 15 showed task-related activity inboth arm-eye and eye modes, and our analysis focused on these cells. We found thatthe introduction of the blink in visual fixation-blink task abolished thetask-related activity of these cells over the course of 2-4 trials. This findingsuggests a role for the pre-SMA in reflecting progression of trials as an updatingof motor instruction.