Author:

Keywords:

Science & Technology, Life Sciences & Biomedicine, Biochemistry & Molecular Biology, Biology, Cell Biology, Life Sciences & Biomedicine - Other Topics, FMRI-ADAPTATION, VISUAL-CORTEX, NEURONS, SELECTIVITY, BRAIN, DYNAMICS, MEMORY, inferotemporal cortex, nonhuman primate, optogenetics, repetition suppression, visual adaptation, Animals, Macaca mulatta, Male, Neurons, Optogenetics, Photic Stimulation, Temporal Lobe, Visual Perception, C32/15/031#53326791, 06 Biological Sciences, 11 Medical and Health Sciences, 17 Psychology and Cognitive Sciences, Developmental Biology, 31 Biological sciences, 32 Biomedical and clinical sciences, 52 Psychology

Abstract:

Neurons in macaque inferior temporal (IT) cortex show a decrease in the response with stimulus repetition, known as repetition suppression (RS). Several mechanisms may contribute to RS in IT, such as firing rate-dependent fatigue and transsynaptic mechanisms, like synaptic depression or reduced input from neurons within the same area or from up- or downstream areas. We examined the role of firing rate fatigue and transsynaptic mechanisms by stimulating directly IT neurons using optogenetics and measured the effect of photo-stimulation on their responses using timing parameters that resulted in RS for visual stimuli. Photo-stimulation of IT neurons resulted in a marginally decreased probability of spiking activity to a subsequent photo-stimulation or to a subsequent low-contrast visual stimulus. This response reduction was small relative to that for repeated visual stimuli and was related to post-stimulation inhibition of the activity during the interval between adapter and test stimuli. Presentation of a visual adapter did not change the response to subsequent photo-stimulation. In neurons whose response to the visual adapter was inhibited by simultaneous photo-stimulation, RS to visual stimuli was unaffected. Overall, these data imply that RS in IT has a transsynaptic origin, with little or no contribution of intrinsic firing rate fatigue. In addition, they suggest a limited contribution of both local synaptic depression and reduced input from nearby IT neurons, whose responses were postulated to be decreased by firing rate fatigue, to RS in IT.