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David J. Freedman; Learning-dependent plasticity of visual encoding in inferior temporal cortex. Journal of Vision 2015;15(12):1420. doi: 10.1167/15.12.1420.
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© ARVO (1962-2015); The Authors (2016-present)
Our ability to recognize complex visual stimuli depends critically on our past visual experience. For example, we easily and seemingly automatically recognize familiar visual stimuli such as a friend’s face, our bicycle, or the characters on a written page. Visual form recognition depends on neuronal processing along a hierarchy of visual cortical areas which culminates in the inferior temporal cortex (ITC), which contains neurons which show exquisite selectivity for complex visual stimuli. Although both passive experience and explicit training can modify or enhance visual selectivity in ITC, the mechanisms underlying this plasticity are not understood.
This talk will describe studies aimed at understanding the impact of experience on visual selectivity in ITC. Monkeys were trained to perform a categorization task in which they classified images as novel or familiar. Neurophysiological recordings from ITC and the prefrontal cortex revealed neuronal encoding of familiarity in both areas. We also examined within-session changes in ITC activity while monkeys viewed a group of initially novel stimuli ~50 times each. Across the ITC population, we observed an increase in stimulus selectivity with increasing repetitions. In particular, we observed a subset neurons that while initially weakly or non-selective, developed strong stimulus selectivity over the course of 10-40 image repetitions. While neurons showing this emergent selectivity were relatively rare (about 10% of all recorded cells), they may provide a mechanism for previously described changes in ITC activity due to stimulus familiarity, and could explain how stimulus selectivity in ITC develops through learning.
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