Abstract
The voluntary control of movement is often tested by using the countermanding, or stop-signal task that sporadically requires the suppression of a movement in response to an incoming stop-signal. Neurophysiological recordings in monkeys engaged in the countermanding task have shown that dorsal premotor cortex (PMd) is implicated in movement control. An open question is whether and how the perceptual demands inherent the stop-signal affects inhibitory performance and their underlying neuronal correlates. To this aim we recorded multi-unit activity (MUA) from the PMd of two male monkeys performing a countermanding task in which the salience of the stop-signals was modulated. Consistently to what has been observed in humans, we found that less salient stimuli worsened the inhibitory performance. At the neuronal level, these behavioral results were subtended by the following modulations: when the stop-signal was not noticeable compared to the salient condition the preparatory neuronal activity in PMd started to be affected later and with a less sharp dynamic. This neuronal pattern is probably the consequence of a less efficient inhibitory command useful to interrupt the neural dynamic that supports movement generation in PMd.
Highlights
Many daily decisions that we make are conditioned by the efficiency with which our brain processes sensory stimuli
Using a perceptual countermanding task that we recently validated in humans[19], we found that less salient Stop stimuli deteriorate inhibitory performance and correspond to longer Stop-signal Reaction Time (SSRT) in non-human primate subjects
Two indices of inhibitory control could be derived from the behavior: the first is the average probability of responding on signal trials [p(respond), i.e., the percentage of signal-respond trials in the session], and the second is the SSRT, computed using the integration method[15]
Summary
Many daily decisions that we make are conditioned by the efficiency with which our brain processes sensory stimuli. The frontal and parietal cortical areas of the primate brain, when studied in decision tasks, contain neurons, the activity of which shows evidence of accumulation dynamics[3,5,6,7,8,9,10], combined eventually with an urgency-to-respond process[11]. In some of these areas (e.g., the lateral intraparietal area [LIP] and the dorsal premotor cortex [PMd]), evidence of sensorimotor transformations emerges—for instance, sensorial information is integrated into a movement preparation activity that is later transformed into an action.
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