Effect of Motivation on Movement Control: Neural Correlates in Dorsal Premotor Cortex

The dorsal premotor cortex (PMd) is a brain area involved in the control of movement. An open question is how the motivation can modulate this function. We trained a macaque monkey to a modified version of the countermanding task, in which Go trials (~65%) require to make a movement after a go signal, while Stop trials (~35%) require to inhibit the reactive movement after a stop signal. In each trial, an initial cue (1000 msec delay) informed about the potential amount of reward that would have been delivered if a correct response would have been produced. The meaning of the cue for correct responses was different. In the Go+Stop- condition the cue indicated more reward for the Go trials and less reward for the Stop trials. The opposite was in the Go-Stop+ condition. The cue was not informative (neutral) for the GoStop condition. We found that the monkey adapted his behavior to the cue value: faster reaction times in Go trials and higher error rate in Stop trials diminished from Go+Stop-, to GoStop and then to Go-Stop+ conditions. In PMd we found that 43/74 neurons recorded distinguished between conditions: some of them started to differentiate between conditions after 500msec from the cue, others close to the go signal. Seventeen/43 neurons were directly involved in movement control and showed different responses to the stop signal presentation depending on the cue presented. These data suggest that in PMd motivational information is integrated into neural mechanism of movement control by a heterogeneous dynamic.