Experience-dependent sharpening of visual shape selectivity in inferior temporal cortex.

Whereas much is known about the visual shape selectivity of neurons in the inferior temporal cortex (ITC), less is known about the role of visual learning in the development and refinement of ITC shape selectivity. To address this, we trained monkeys to perform a visual categorization task with a parametric set of highly familiar stimuli. During training, the stimuli were always presented at the same orientation. In this experiment, we recorded from ITC neurons while monkeys viewed the trained stimuli in addition to image-plane rotated versions of those stimuli. We found that, concomitant with the monkeys' behavioral performance, neuronal stimulus selectivity was stronger for stimuli presented at the trained orientation than for rotated versions of the same stimuli. We also recorded from ITC neurons while monkeys viewed sets of novel and familiar (but not explicitly trained) randomly chosen complex stimuli. We again found that ITC stimulus selectivity was sharper for familiar than novel stimuli, suggesting that enhanced shape tuning in ITC can arise for both passively experienced and explicitly trained stimuli.