Prefrontal Delay-Period Activity Reflects the Decision Process of a Saccade Direction during a Free-Choice ODR Task
Department of Cognitive and Behavioral Sciences, Graduate School of Human and Environmental Studies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
Address correspondence to email: sfunahashi{at}mbox.kudpc.kyoto-u.ac.jp.
To examine how delay-period activity participates in the decision of a saccade direction, we analyzed prefrontal activity while monkeys performed 2 tasks: oculomotor delayed-response (ODR) and self-selection ODR (S-ODR) tasks. In the ODR task, monkeys were required to make a memory-guided saccade to the cue location after a 3-s delay. In the S-ODR task, 4 identical visual cues were presented simultaneously during the cue period and monkeys were required to make a saccade in any one direction after the delay. Delay-period activity was observed in both tasks in the same neuron with similar directional preferences. Neurons with delay-period activity were classified into several groups based on the temporal pattern of the activity itself and of the strength of the directional selectivity. Among these, neurons with an increasing type of delay-period activity with persistent directional selectivity throughout the delay period in the ODR task also showed directional delay-period activity in the S-ODR task. These results indicate that an increasing type of delay-period activity, which is thought to represent motor information, plays an important role in generating and enhancing directional bias in the S-ODR task and therefore contributes significantly to the decision process of the saccade direction in the S-ODR task.
Key Words: decision making • directional delay-period activity • free-choice saccade task • prefrontal cortex • single-neuron activity