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Knight RS, Chen T, Center EG, Gratton G, Fabiani M, Savazzi S, Mazzi C, Beck DM. Bypassing input to V1 in visual awareness: A TMS-EROS investigation. Neuropsychologia 2024; 198:108864. [PMID: 38521150 PMCID: PMC11194103 DOI: 10.1016/j.neuropsychologia.2024.108864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 02/07/2024] [Accepted: 03/18/2024] [Indexed: 03/25/2024]
Abstract
Early visual cortex (V1-V3) is believed to be critical for normal visual awareness by providing the necessary feedforward input. However, it remains unclear whether visual awareness can occur without further involvement of early visual cortex, such as re-entrant feedback. It has been challenging to determine the importance of feedback activity to these areas because of the difficulties in dissociating this activity from the initial feedforward activity. Here, we applied single-pulse transcranial magnetic stimulation (TMS) over the left posterior parietal cortex to elicit phosphenes in the absence of direct visual input to early visual cortex. Immediate neural activity after the TMS pulse was assessed using the event-related optical signal (EROS), which can measure activity under the TMS coil without artifacts. Our results show that: 1) The activity in posterior parietal cortex 50 ms after TMS was related to phosphene awareness, and 2) Activity related to awareness was observed in a small portion of V1 140 ms after TMS, but in contrast (3) Activity in V2 was a more robust correlate of awareness. Together, these results are consistent with interactive models proposing that sustained and recurrent loops of activity between cortical areas are necessary for visual awareness to emerge. In addition, we observed phosphene-related activations of the anteromedial cuneus and lateral occipital cortex, suggesting a functional network subserving awareness comprising these regions, the parietal cortex and early visual cortex.
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Affiliation(s)
- Ramisha S Knight
- Beckman Institute, University of Illinois.405 N Mathews Avenue, Urbana, IL, USA; Aptima, Inc. 2555 University Blvd, Fairborn, OH, USA
| | - Tao Chen
- Beckman Institute, University of Illinois.405 N Mathews Avenue, Urbana, IL, USA; Department of Psychology, University of Illinois. 601 E John Street, Champaign, IL, USA.
| | - Evan G Center
- Beckman Institute, University of Illinois.405 N Mathews Avenue, Urbana, IL, USA; Department of Psychology, University of Illinois. 601 E John Street, Champaign, IL, USA; Center for Ubiquitous Computing, University of Oulu, Oulu, Finland
| | - Gabriele Gratton
- Beckman Institute, University of Illinois.405 N Mathews Avenue, Urbana, IL, USA; Department of Psychology, University of Illinois. 601 E John Street, Champaign, IL, USA
| | - Monica Fabiani
- Beckman Institute, University of Illinois.405 N Mathews Avenue, Urbana, IL, USA; Department of Psychology, University of Illinois. 601 E John Street, Champaign, IL, USA
| | - Silvia Savazzi
- Perception and Awareness (PandA) Lab, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Chiara Mazzi
- Perception and Awareness (PandA) Lab, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Diane M Beck
- Beckman Institute, University of Illinois.405 N Mathews Avenue, Urbana, IL, USA; Department of Psychology, University of Illinois. 601 E John Street, Champaign, IL, USA.
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