Enhanced neural plasticity in monkey TE compared to TEO during learning of a feature-ambiguous visual categorization task

Primates can categorize images quickly based on the similarity of visual features. We previously showed that two subregions of inferior temporal cortex (IT), TEO and TE, contribute to visual categorization to differing extents. To investigate the neural plasticity underlying visual categorization, we recorded simultaneously from TE and TEO while two male monkeys learned a visual categorization task. Category specificity – i.e., distinguishing between exemplars of different categories, and category generalization – i.e., generalizing across exemplars within the same category, were initially stronger in TEO than in TE but increased across learning only in the TE neuronal population, not in TEO. Neural representations in TE, but not TEO, correlated with behavioral performance. TE and TEO can contribute complementary, partially independent category information. However, TEO does not add learning-relevant variance across days. TE showed greater categorical enhancement in correct trials than TEO, relative to error trials. Single-neuron analyses revealed that category selectivity in TE strengthened with learning, primarily through enhanced encoding of one category. Combined with the findings from lesion studies, our results suggest that although TE and TEO can represent complementary information, neural plasticity in area TE likely plays a more fundamental role in supporting visual category learning.