Functional clusters for shape, texture, and motion encoding in macaque V2
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Macaque primary visual cortex (V1) exhibits exquisite columnar organization, while midlevel area V4 does not. Here we investigated the functional organization and representational bases of intervening area V2 with high-density Neuropixels recordings and a variety of visual stimuli—shape, texture, drifting grating, and translational motion patches. We observed dense clusters of similarly tuned neurons often spanning ∼500 µm for shape and motion stimuli, and larger for texture stimuli, consistent with a columnar structure. In terms of representational bases, V2 responses were largely explained by stimulus features based on local image statistics: shape tuning is well-modeled by a linear combination of orientation filters, and direction selectivity is stronger with surface compared to object motion, in striking contrast to V4. Overall, our results support the progression from columns to sparse clusters as neuronal representations transform from encoding local features and feature conjunctions in V1/V2 to a high-dimensional object-based code in V4.
Significance Statement
By recording hundreds of neurons simultaneously across layers of macaque visual area V2, we show the first evidence of exquisite fine-scale functional clusters that encode higher-order shape, texture, and motion features, extending well beyond the classic orientation-selective columns seen in area V1. Comparative analyses with V4 further reveal distinct representational bases and organization patterns between adjacent cortical areas, offering insights into how columnar organization is preserved in early visual areas (V1 and V2) but markedly attenuated in higher-order cortex such as V4.
