Neural signatures of visual awareness independent of postperceptual processing.
Michael A Cohen, Cole Dembski, Kevin Ortego, Clay Steinhibler, Michael Pitts
Cerebral cortex (New York, N.Y. : 1991) November 5, 2024 DOI: 10.1093/cercor/bhae415 via PubMed
Summary
AI-generated from the abstractUsing electroencephalography and a no-report visual masking paradigm, stimulus visibility was manipulated by varying the time between stimuli and masks in linear steps (17, 33, 50, 67, and 83 ms). Awareness increased nonlinearly, with stimuli never seen at the two shortest intervals, always seen at the two longest, and 50% seen at the intermediate interval. A neural signal closely linked to perceptual awareness, independent of task, was identified: a fronto-central event-related potential called the N2 (~250 to 300 ms). Earlier signals reflected the linear manipulation of stimulus strength, while later signals like P3b and temporal generalization of decoding were tied to task performance, appearing only in the report condition. These findings inform debates regarding theories of consciousness.
Study at a glance
| Characteristics | Experimental study Peer reviewed |
|---|---|
| Interventions | 33 50 67 83 ms) |
| Keywords | EEG Attention Awareness Consciousness Perception |
| Citations | 20 |
| Key finding | A fronto-central N2 event-related potential (~250 to 300 ms) is closely linked to perceptual awareness, independent of task performance. |
Abstract
What are the neural processes associated with perceptual awareness that are distinct from preconscious sensory encoding and postperceptual processes such as reporting an experience? Using electroencephalography and a no-report visual masking paradigm, we manipulated stimulus visibility by varying the time between stimuli and masks in linear steps (17, 33, 50, 67, and 83 ms). Awareness increased nonlinearly, with stimuli never seen at the two shortest intervals, always seen at the two longest, and 50% seen at the intermediate interval. Separate report and no-report conditions were used to isolate awareness from task performance. Our results revealed a neural signal closely linked to perceptual awareness, independent of the task: a fronto-central event-related potential that we refer to as the N2 (~250 to 300 ms). Earlier event-related potential signals reflected the linear manipulation of stimulus strength, while later signals like P3b and temporal generalization of decoding were tied to task performance, appearing only in the report condition. Taken together, these findings inform current debates regarding theories of consciousness and offer new avenues for exploring the neural mechanisms supporting conscious processing.