High-Density Recording Reveals Sparse Clusters (But Not Columns) for Shape and Texture Encoding in Macaque V4.

Area of Science:

• Neuroscience
• Visual Cortex Organization

Background:

• Macaque area V4 neurons are known for shape and texture selectivity.
• The laminar functional organization of area V4 remains largely unknown.

Purpose of the Study:

• To investigate the functional organization of shape and texture tuning across cortical layers in macaque area V4.
• To determine if neurons with similar tuning properties cluster in specific layers or form columnar structures.

Main Methods:

• Utilized high-density Neuropixels probes in two awake macaque monkeys.
• Simultaneously recorded the shape and texture tuning of numerous neurons across different cortical layers.

Main Results:

• Identified sporadic clusters of neurons with similar shape and texture tuning, comprising approximately 20% of recorded neurons.
• These clusters were confined to specific layers and rarely exhibited a columnar organization.
• Similar organization patterns were observed even for strongly driven neurons with contrast-invariant tuning.

Conclusions:

• Functional organization in macaque area V4 is not columnar for specific shape and texture features.
• Organization appears to operate at a coarser scale, potentially related to stimulus categories (e.g., 3D cues) and spatial scales.
• This organization may result from the integration of diverse inputs, leading to complex tuning manifolds in V4 neurons.