Functional Clusters for Shape, Texture, and Motion Encoding in Macaque V2

Area of Science:

• Neuroscience
• Visual System Organization
• Cortical Processing

Background:

• Macaque primary visual cortex (V1) shows clear columnar organization, while area V4 does not.
• The functional organization of the intervening area V2 is less understood.
• Understanding V2 is crucial for mapping the progression of visual information processing.

Purpose of the Study:

• To investigate the functional organization and representational bases of macaque visual area V2.
• To compare the organization of V2 with V1 and V4.
• To understand how neuronal representations transform across visual areas.

Main Methods:

• High-density Neuropixels recordings in three macaques (one male, two females).
• Presentation of diverse visual stimuli including shape, texture, drifting gratings, and motion patches.
• Analysis of neuronal tuning and clustering across V2 layers.

Main Results:

• Dense clusters of similarly tuned neurons were observed in V2, spanning approximately 500 µm, indicating columnar structure.
• V2 responses were explained by local image statistics, with shape tuning modeled by orientation filters.
• Direction selectivity in V2 was stronger for surface motion than object motion, contrasting with V4.

Conclusions:

• Macaque V2 exhibits fine-scale functional clusters, extending beyond V1's orientation-selective columns.
• Neuronal representations transition from local feature encoding in V1/V2 to object-based codes in V4.
• Columnar organization is present in early visual areas (V1, V2) but attenuated in higher areas (V4).