Long-lasting neural activity indexed by cognitive function underlying unconscious color perception

Consciousness generation and processing are vital topics in neuroscience. Researchers compare neural activation between conscious and unconscious conditions in order to identify the neural correlates of consciousness. Visual perception studies have explored the relationship between electroencephalography (EEG) signals and consciousness, leading to breakthroughs. Yet, inconsistencies in event-related potential (ERP) components, subliminal activity duration, and the role of higher cognitive function persist due to methodological challenges and confusion regarding conscious and post-perceptual processes. In our study, we designed a subliminal color perception experiment using the oddball paradigm. We examined neural activity evoked by supraliminal/subliminal stimuli of varying color saturation. A rigorous perception threshold detection schema ensured reliability. Different task paradigms (active or passive) and immediate perception reports were included to study the interaction between post-perceptual and subliminal processes. EEG data under varying perception and task conditions were compared. Under subliminal conditions, the traditional positive P300 wave vanished, replaced by significant negative activity in the P3b time window (300-600 ms) and late slow wave (LSW, 600-1000 ms). These subliminal activities weakened or vanished under the passive task condition. Source reconstruction and dynamic causality modeling revealed reduced connectivity in subliminal conditions among the dorsolateral prefrontal cortex (DLPFC), posterior parietal cortex (PPC), secondary visual cortex (V2), and amygdala. The backward connection from DLPFC to PPC and V2 diminished during the passive task. Overall, our study uncovered significant negative activation of the P3b and LSW during subliminal color perception, indicating nuanced long-lasting unconscious neural activity and the modulation effect of higher cognitive function on consciousness.