Posterior but not frontal neural signatures of subjective visibility in report-independent EEG decoding

Abstract

A central question in consciousness research is whether perceptual awareness arises predominantly from activity in posterior sensory regions or from later frontal processes associated with access and report. Empirical tests of these alternatives are challenging because most paradigms rely on explicit perceptual reports, introducing motor and decisional confounds. Here, we used an electroencephalography design combining two independent tasks to isolate neural signatures of subjective visibility while minimizing report-related activity. Participants viewed lateralized gratings in a backward-masking task and rated their subjective visibility, while in a separate no-report task they viewed unmasked gratings without reporting. Classifiers were trained on stimulus location in the no-report task and tested on masked trials sorted by subjective visibility in the masking task. This cross-decoding approach isolates stimulus-specific neural representations that generalize across tasks and are therefore independent of reporting and decision processes. Decoding revealed a reliable difference between subjectively visible and invisible stimuli in an early time window from 130 to 170 milliseconds, driven by posterior sensors over occipital, temporal, and parietal regions. No corresponding effects were observed over frontal sensors. These results indicate that subjective awareness is associated with early, posterior neural representations, whereas frontal activity observed in report-based paradigms likely reflects post-perceptual processing rather than awareness per se.