The representational geometry of naturalistic textures in macaque V1 and V2.

Our understanding of visual cortical processing has relied primarily on studying the selectivity of individual neurons in different areas. A complementary approach is to study how the representational geometry of neuronal populations differs across areas, which can reveal encoding strategies difficult to infer from single neuron responses. We measured neuronal population responses in primary visual cortex (V1) and area V2 of macaque monkeys to naturalistic textures. Responses were lower dimensional in V2 than V1, and there was a better alignment among V2 population responses to different textures. The representational geometry in V2 afforded better discriminability between out-of-sample textures. We performed complementary analyses of standard convolutional network models, which did not replicate the representational geometry of cortex. We conclude that from V1 to V2 the visual representation changes to emphasize a low-dimensional, systematic encoding of different textures and of different instantiations of each texture.