Deliberation and Commitment in the Premotor and Primary Motor Cortex during Dynamic Decision Making

Neurophysiological studies of decision making have primarily focused on decisions about information that is stable over time. However, during natural behavior, animals make decisions in a constantly changing environment. To investigate the neural mechanisms of such dynamic choices, we recorded activity in dorsal premotor (PMd) and primary motor cortex (M1) while monkeys performed a two-choice reaching task in which sensory information about the correct choice was changing within each trial and the decision could be made at any time. During deliberation, activity in both areas did not integrate sensory information but instead tracked it and combined it with a growing urgency signal. Approximately 280 ms before movement onset, PMd activity tuned to the selected target reached a consistent peak while M1 activity tuned to the unselected target was suppressed. We propose that this reflects the resolution of a competition between the potential responses and constitutes the volitional commitment to an action choice.