Subjective visual awareness emerges prior to P3

Area of Science:

• Neuroscience
• Cognitive Science
• Psychology

Background:

• Neural correlates of visual awareness are difficult to distinguish from post-perceptual processing like response reporting.
• Previous studies often conflate awareness with response selection, making it challenging to pinpoint the neural basis of subjective experience.

Purpose of the Study:

• To dissociate electrophysiological correlates of visual awareness from those associated with response selection and post-perceptual processing.
• To investigate the temporal dynamics of neural activity related to conscious visual perception.

Main Methods:

• Participants performed GO-NOGO tasks under conditions where responses were contingent on awareness (aware-GO) or unawareness (unaware-GO).
• Event-related potentials (ERPs) were measured for both aware and unaware trials, irrespective of response requirements.
• Specific ERP components, N200 and P3, were analyzed over occipital and posterior temporal regions.

Main Results:

• An enhanced N200 amplitude (180-280 ms) over the occipital and posterior temporal cortex, termed visual awareness negativity (VAN), was observed in aware trials compared to unaware trials.
• The VAN effect was independent of response requirements, suggesting it reflects a pre-response correlate of awareness.
• P3 amplitude (350-450 ms) was also enhanced in aware trials but was modulated by response mapping, indicating its involvement in post-perceptual processing.

Conclusions:

• The visual awareness negativity (VAN) provides evidence for an early neural correlate of visual awareness.
• The findings support theories positing that visual awareness emerges before later post-perceptual processes reflected by P3.
• This research helps to disentangle the neural mechanisms underlying conscious experience from those involved in action execution.