Sequential neural dynamics underlie unconscious integration and conscious perception of visual stimuli

Summary

Later events can change how earlier ones are perceived, a phenomenon called postdiction. The Sequential Metacontrast paradigm integrates unconscious vernier offsets over hundreds of milliseconds before conscious perception. Using EEG in humans, researchers identified two neural activity stages: an early occipital pattern around 200 milliseconds after the first vernier, linked to unconscious processing, and a later centro-parietal pattern from 400 to 600 milliseconds after the stream begins, associated with the integrated percept and behavioral report. This transition may mark the shift from unconscious encoding to conscious integration.

Study at a glance

Abstract

In some forms of postdictive phenomena, later events influence the perception of earlier ones, suggesting that conscious perception may be preceded by extended periods of unconscious processing. An example is the Sequential Metacontrast (SQM) paradigm, in which vernier offsets are unconsciously integrated over several hundred milliseconds before conscious perception. Obviously, the integrated percept can only emerge after each individual element in the stream has been processed. Thus, the SQM provides a unique opportunity to dissociate unconscious from conscious stages of visual processing, as these stages are well separated in time. Using electroencephalography (EEG) recordings in human participants 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 to 600 ms after SQM onset) associated with the integrated percept and the 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.

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