Visual and anticipatory bias in three cortical eye fields of the monkey during an adaptive decision-making task

To examine the role of three cortical eye fields during internally guided decision-making processes, we recorded neuronal activities in the frontal eye field (FEF), supplementary eye field (SEF), and lateral intraparietal cortex (LIP) using a free-choice delayed saccade task with two synchronized targets. Although the monkeys must perform the task in a time-locked manner, they were free to choose either the receptive field (RF) target or the nonreceptive field (nRF) target to receive reward. In all three areas we found neurons with stronger activation during trials when the monkey was going to make a saccade to the RF target (RF trials) than to the nRF target (nRF trials). Modulation occurred not only during target presentation (visual bias) but also before target presentation (anticipatory bias). The visual bias was evident as an attenuated visual response to the RF stimulus in nRF trials. The anticipatory bias, however, was seen as an enhancement of pretarget activity in the RF trials. We analyzed the activity during the 500 msec before target presentation and found that 22.5% of FEF and 31.3% of LIP neurons and 49.1% of SEF neurons showed higher activity during the RF trials. To more accurately determine when each neuron started to show preferential activity, we used a new inverse interspike interval analysis procedure. Our results suggest that although all three cortical eye fields reflect attentional and intentional aspects of sensorimotor processing, SEF plays an earlier and perhaps more cognitive role in internally guided decision-making processes for saccades.