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Bypassing input to V1 in visual awareness: A TMS-EROS investigation
Ramisha S Knight1, Tao Chen2, Evan G Center3
1Beckman Institute, University of Illinois.405 N Mathews Avenue, Urbana, IL, USA; Aptima, Inc. 2555 University Blvd, Fairborn, OH, USA.
Neuropsychologia
|March 23, 2024
Summary
Visual awareness requires feedback loops between brain regions, not just initial visual input. Recurrent activity in the parietal cortex and visual areas like V2 is crucial for conscious perception.
Area of Science:
- Neuroscience
- Cognitive Science
- Visual Perception
Background:
- Early visual cortex (V1-V3) is essential for visual awareness via feedforward input.
- The role of re-entrant feedback to early visual areas in awareness remains unclear.
- Dissociating feedback from feedforward activity is methodologically challenging.
Purpose of the Study:
- To investigate the necessity of feedback activity in early visual cortex for visual awareness.
- To explore the neural correlates of awareness using phosphene generation via TMS.
- To identify the functional network involved in visual awareness.
Main Methods:
- Single-pulse transcranial magnetic stimulation (TMS) over the posterior parietal cortex to induce phosphenes without direct visual stimulation.
- Event-related optical signal (EROS) imaging to measure neural activity under the TMS coil.
- Analysis of temporal dynamics of neural activity related to phosphene awareness.
Main Results:
- Posterior parietal cortex activity at 50 ms post-TMS correlated with phosphene awareness.
- Awareness-related activity was found in V1 at 140 ms post-TMS.
- V2 activity showed a more robust correlation with awareness compared to V1.
Conclusions:
- Sustained, recurrent activity loops between cortical areas are necessary for visual awareness.
- A functional network including parietal cortex, V1, V2, anteromedial cuneus, and lateral occipital cortex supports visual awareness.
