Anticipatory activity of motor cortex neurons in relation to direction of an intended movement

Abstract

1. Monkeys were trained to 1) hold a handle in a central zone midway between "push" and "pull" while awaiting 2) an instruction telling them how to respond to a subsequent 3) perturbation, which triggered the instructed movement and was followed by 4) a reward if the movement was correct. 2. There were two sorts of instructions: push and pull. When the pull instruction had preceded the perturbation, the monkey responded to the perturbation by pulling, whereas after a push instruction, the monkey responded to the perturbation by pushing. 3. Recordings in pre- and postcentral sensorimotor cortex revealed instruction-induced changes of neuronal activity during the period intervening between the instruction and the perturbation-triggered movement. Effects of the instruction were differential depending on which of the two instructions was given, such differential responses to the instruction being detected in 61% of precentral pyramidal tract neurons (PTNs), 44% of precentral non-PTNs, and 11% of postcentral neurons. 4. Since motor cortex PTN axons end on alpha and gamma motoneurons and on interneurons of the spinal cord, changes of PTN activity with "intention" or "motor set" provide a mechanism for suprasegmental control and presetting of spinal cord reflex excitability specific to the nature of an impending movement.

Robust neuronal dynamics in premotor cortex during motor planning

“…Neurons in frontal and parietal cortex show slow dynamics, including persistent and ramping activity, related to motor planning [1][2][3][4] , action timing 5,6 , working memory [7][8][9][10] and decision making [11][12][13] . Neurons have intrinsic time constants on the order often milliseconds 14 .…”

A vector-integration-to-endpoint model for performance of viapoint movements

“…Vector encoding as a design principle for the control of arm movement is supported by neurophysiological evidence on primate cells from several precentral (e.g., areas 4 and 6) and postcentral (e.g., area 5) regions of the cerebral cortex (Evarts & Tanji, 1974;Georgopoulos, 1986;Georgopoulos et a!., 1982;Lacquaniti eta!. 1995;Schwartz eta!., 1988;Tanji & Evarts, 1976). These studies measured the activity levels and activity level changes of cell populations in arm controlling areas of the cortex in monkeys trained to execute pointing movements in two or three-dimensional space.…”

Comparison of neuronal activity in the supplementary motor area and primary motor cortex

“…In subsequent studies, the development of preparation for the direction of intended movement was found to be reflected in preparatory activity in the SMA [2,31]. However, the preparatory activity or motor set reflecting direction of intended movement is found in many other motor areas in the brain, including the MI [20,46,56,66], and therefore, not a unique observation in the SMA. Are there any behavioral tasks that call for preparatory activity preferentially in the SMA?…”