Early and Late ERP Correlates of Conscivousness- A Direct Comparison Between Visual and Auditory Modalities.

The majority of previous research on neural correlates of consciousness (NCC) have used the visual system as a model. However, to what extent reported findings generalize to other sensory modalities has not been comprehensively investigated. To fill this gap we directly compared visual and auditory NCCs by testing the same group of participants with two analogous procedures. Participants were presented with near-threshold visual and auditory stimuli followed by a detection task and Perceptual Awareness Scale (PAS). On the behavioral level, as expected from visual awareness studies, PAS ratings were highly correlated with accuracy in the detection task. Analysis of EEG data revealed that analogous ERP components-early visual or auditory awareness negativity (VAN and AAN) were related to perceptual awareness, but regarding late positivity (LP), it was related to perceptual awareness only in the visual modality. Further, we found that VAN and visual LP exhibited shorter latencies than respective auditory components suggesting earlier access of visual stimuli to consciousness, compared to auditory ones. Finally, neither estimated perceptual thresholds nor amplitudes and latencies of the awareness-related ERPs components were correlated between modalities, suggesting a lack of a close link between visual and auditory perceptual mechanisms. Therefore, the observed differences between visual and auditory modalities indicate the investigated NCC are rather modality-specific, and thus that neither of the proposed measures track consciousness independently to the content-related processing.