Search target selection in monkey prefrontal cortex.

To explore a visual scene, the brain must detect an object of interest and direct the eyes to it. To investigate the brain's mechanism of saccade target selection, we trained monkeys to perform a visual search task with a response delay and recorded neuronal activity in the prefrontal (PF) cortex. Even though the monkey was not allowed to express its choice until after a delay, the response field of a class of PF neurons was able to differentiate between target and distractors from the very beginning of their response (135 ms). Strong responses were obtained only when the target was presented at the field. Neurons responded much less during a nonsearch task in which saccade target was presented alone in this response field. These results suggest that the PF cortex may be involved in the decision-making process and the focal attention for saccade target selection.