Optogenetic Inactivation Modifies Monkey Visuomotor Behavior

A critical technique for understanding how neuronal activity contributes to behavior is determining whether perturbing it changes behavior. The advent of optogenetic techniques allows the immediately reversible alteration of neuronal activity in contrast to chemical approaches lasting minutes to hours. Modification of behavior using optogenetics has had substantial success in rodents but has not been as successful in monkeys. Here, we show how optogenetic inactivation of superior colliculus neurons in awake monkeys leads to clear and repeatable behavioral deficits in the metrics of saccadic eye movements. We used our observations to evaluate principles governing the use of optogenetic techniques in the study of the neuronal bases of behavior in monkeys, particularly how experimental design must address relevant parameters, such as the application of light to subcortical structures, the spread of viral injections, and the extent of neuronal inactivation with light. ► Optogenetic techniques modulate behavior in nonhuman primates as they do in rodents ► Precise saccadic deficits followed optogenetic inactivation of superior colliculus ► Deficit size resulted from interaction of viral and light spread in groups of neurons ► Immediate and reversible effects provide critical tools for primate circuit analysis Optogenetic techniques provide a temporally and spatially precise method for modulating neuronal activity. Cavanaugh et al. apply these methods to specific motor circuits to successfully alter eye movements in the nonhuman primate, revealing certain principles and constraints of such techniques.