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Arash Afraz, Edward S. Boyden, James J DiCarlo; Optogenetic and pharmacological suppression of face-selective neurons reveal their causal role in face discrimination behavior.. Journal of Vision 2014;14(10):600. doi: 10.1167/14.10.600.
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© ARVO (1962-2015); The Authors (2016-present)
Using optogenetic and pharmacological interventions we suppressed the activity of face-selective neurons in the inferior temporal (IT) cortex of macaque monkeys performing a facial gender discrimination task. Prior to behavioral testing, we determined the neural selectivity profile using a passive fixation paradigm and a large (~3x2mm) cluster of face-selective neurons was targeted for suppression. Adeno Associated Virus 8 was used to express ArchT at targeted location. Temporally-delimited (200 ms) optogenetic suppression of visually evoked activity at those locations was verified with custom made optrodes. The effect of optical suppression was compared with the effect of pharmacological silencing via muscimol microinjection at the same location. Both pharmacological and optogenetic suppression of these IT face-selective neurons produced a deficit in face discrimination. The deficit was specific to the contralateral visual hemifield, and it was not found for other locations in IT where the neuronal responses were not face selective. Specifically, optogenetic suppression of face neurons in randomly interleaved trials led to a significant drop in discrimination performance (median= 1.8%, mean=1.98%, t(17)=6.2, p<0.0001). Muscimol silencing of the same neurons caused a drop in discrimination performance (median= 4.9%, mean=5.53%, t(6)=3.98, p<0.01) 30 minutes after the injection, which persisted for the following 2 hours. The larger behavioral effect of muscimol-induced suppression is consistent with its larger spatial spread in cortex. Our results establish a causal link between the activity of some IT face-selective neurons and at least one type of face discrimination behavior. The demonstrated utility of optogenetic tools for inducing specific behavioral effects in a face discrimination task opens the door for applying the technical advantages of optogenetics to studies of high-level vision.
Meeting abstract presented at VSS 2014
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