Abstract
A macaque monkey was trained to behaviorally detect 200ms impulses of optogenetic stimulation delivered to its inferior temporal (IT) cortex while viewing images of objects. In each trial, the image displayed was independent of stimulation condition, and the animal was only rewarded for correctly identifying whether the trial did or did not contain stimulation.
To stimulate IT cortex, we used the depolarizing opsin C1V1 targeting cells that express CAMKIIa in combination with a novel, chronically implanted optical array composed of 24 individually controlled LEDs each capable of producing up to 60mW green (527nm) light.
The animal was able to robustly detect optical impulses delivered to its transduced cortex (mean 89% correct, chance level 50%, Chi-squared p<0.0001). To the best of our knowledge, this is the largest behavioral “effect size” of optogenetic brain perturbation in a nonhuman primate reported to date. Moreover, we observed that the animal’s performance on this task was heavily influenced by visual input to the retinae. The performance in detection of the optical impulse ranged from 74% to 100% correct depending on what image was viewed during the trial (bootstrapping, p<.001).
These findings reveal that for a given imageset, there exists a unique “detection profile” that is composed of the animal’s cortical stimulation detection rates while viewing each image in the set.
Changing the cortical position of stimulation changes the detection profile; across days of testing, detection profile is more correlated within a stimulation site, than between two different sites (bootstrapping, p<.001).
These results show that optogenetics can be used to induce large behavioral effects in nonhuman primates. Strong interaction of the task with visual input suggests that the animal detects the cortical stimulation based on an induced visual event.