Michael Pitts¹, Gennadiy Belonosov², Oscar Ferrante³, Ling Liu⁴, Rony Hirschhorn², Ole Jensen⁵, Huan Luo⁴, Lucia Melloni⁶, Liad Mudrik²; ¹Reed College, ²Tel Aviv University, ³University of Surrey, ⁴Peking University, ⁵University of Oxford, ⁶Ruhr-Universität Bochum

What is the difference in neural processing when we are aware versus unaware of a stimulus? Previous attempts to identify neural signals uniquely associated with visual awareness have faced several challenges. A critical one has been to isolate neural events linked with perception from those associated with reporting one’s perception. To address this, we developed a dual-task inattention paradigm in which participants played an engaging video-game as the primary task, while face and object stimuli were occasionally presented in the background. In 1/3 of the trials, a secondary task was presented immediately after stimulus offset (500ms post-stimulus-onset): the game was paused and participants were prompted to report whether they just saw a stimulus. We first analyzed MEG-EEG data from the report trials. We then trained a pattern classifier to differentiate reported-seen versus reported-unseen trials, and used it to label the remaining 2/3 of the EEG data (no-report trials). In the report trials, we found a visual awareness negativity (VAN; ~220-270ms) followed by a fronto-central negativity (fcN2) and concurrent late bilateral occipital positivity (LBOP) from ~320-550ms. The P3b was also evident but only at ~800-1000ms post-stimulus (~300-500ms after the report-prompts). In the classifier-labeled no-report trials, we found the VAN and fcN2/LBOP with no evidence for P3b. These results demonstrate the potency of this paradigm and classification approach for isolating neural events linked with conscious perception from perceptual-reports. They also suggest that after the VAN, there may be a second stage of processing necessary for visual awareness, indexed here by the fcN2/LBOP.

Acknowledgements: Templeton World Charity Foundation