Optogenetic disruption of memory-drive, oculomotor behavior in the non-human primate

Abstract

Pharmacological inactivation studies have shown that the frontal eye field (FEF) is critical for executing saccades to remembered locations. FEF neurons increase their firing rate during the three epochs of the memory-guided saccade task: visual stimulus presentation, the delay interval, and motor preparation. It is unclear, though, whether FEF activity during each epoch is necessary for memory-guided saccade execution. To address this question, techniques for millisecond-precise optical inactivation of the primate brain were invented. A red-shifted halorhodopsin (Jaws) and a novel large-volume tissue illuminator were used in two rhesus macaques to inactivate part of the FEF at different times during the memory-guided saccade task. Neuronal recordings showed that the inactivated tissue volume (i.e., the volume where the firing rate of >80% of neurons decreased by >80%) spanned several cubic millimeters, which is consistent with histological findings. When the target was in the inactivated receptive field, error rates (i.e., failures to execute memory-guided saccades to the proper target location) increased in both monkeys with inactivation during either the target, delay, or motor period. This implies that FEF neuronal activity contributes to performance throughout the memory-guided saccade task.