Contributions of prefrontal cue-, delay-, and response-period activity to the decision process of saccade direction in a free-choice ODR task

To examine how the dorsolateral prefrontal cortex (DLPFC) contributes to the decision process of the saccade direction, we recorded single-neuron activity while two monkeys performed two oculomotor delayed-response (ODR) tasks. In an ordinary ODR task, monkeys were required to make a memory-guided saccade to the cue location after a 3-s delay. In a self-selection version of the ODR task (S-ODR), four identical visual cues were presented simultaneously at the cue period, and monkeys were required to make a saccade toward any one of four directions after a 3-s delay. By comparing the same neuron's activity between two tasks, we found (1) neurons having directional cue-period activity in the ODR task did not show directionally selective activity in the S-ODR task, (2) neurons having directional pre-saccadic activity showed highly similar directional preferences in two tasks and exhibited temporal coupling between the onset of pre-saccadic activity and the initiation of saccadic eye movements, (3) neurons with directional delay-period activity in the ODR task exhibited similar directional preferences and showed gradual increase in the strength of the directional selectivity toward the end of the delay period in the S-ODR task. These results suggest that directional delay-period activity contributes to the decision process of the saccade direction in the S-ODR task, while directional cue-period and pre-saccadic activities do not. The gradual increase of the directional selectivity in delay-period activity might correspond to neural correlates of the decision process of the saccade direction in the S-ODR task.