Decoding unconscious events and their transition to a unified percept in visual spatio-temporal integration

In postdictive effects, where later events influence the perception of earlier ones, conscious perception is preceded by extended periods of unconscious processing. This is evident in the Sequential Metacontrast (SQM) paradigm, in which vernier offsets are unconsciously integrated over several hundred milliseconds. Regardless of whether one or multiple verniers are shown, only a single offset is perceived along a motion stream. The SQM, along with other postdictive phenomena, thus provides a unique opportunity to dissociate unconscious from conscious stages of visual processing, as these stages are well separated in time. Using EEG during the SQM, we identified two distinct stages of neural activity: an early occipital EEG activity pattern (∼200 ms after the initial vernier) associated with unconscious processing, and a later centro-parietal EEG pattern (∼400-600 ms after SQM onset) associated with the integrated percept and behavioral report. We propose that the transition between these neural patterns marks the shift from unconscious encoding of individual visual stimuli to their integrated percept.