Overlapping functional micro-organization of orientation and spatial frequency maps in the visual cortex.

Objective: The visual cortex plays a crucial role in integrating multiple stimulus features, such as orientation tuning and spatial frequency tuning , to form coherent perceptual representations of the visual environment. Although previous research has hinted at the presence of overlapping maps for orientation and spatial frequency tuning in the visual cortex, clear evidence demonstrating how these features are jointly organized functionally is scarce.

Methods: To address this, we performed multiunit electrophysiological recordings in the primary visual cortex (V1) of anesthetized cats. We presented visual stimuli consisting of drifting sine-wave gratings under two experimental conditions: varying the orientation while keeping spatial frequency constant and varying spatial frequency while maintaining fixed orientations at 0° or 90°. Neuronal responses were analyzed by fitting tuning curves to quantify preferred orientations and spatial frequencies. Functional connectivity between neurons was then assessed using cross-correlogram analysis.

Results: Our results showed that neurons with similar orientation and spatial frequency tuning, exhibited significantly stronger connectivity at 0° orientation, whereas this effect was not observed at 90°. These results indicate that the organization of neuronal networks in V1 is stimulus-dependent and that overlapping ensembles encode these features in a coordinated manner. These results are important for understanding how complex features are integrated within the visual system, and more broadly, how the brain processes and combines information.

Conclusion: Such feature-based connectivity likely enhances the visual cortex's ability to efficiently process complex stimuli, supporting the idea that perceptual integration relies on the dynamic interplay of neurons sharing similar tuning properties.