During sleep, the brain retains the ability to preactivate representations of specific sound features, such as tone frequency, but loses the capacity to track higher-order statistical associations between sounds. Using EEG and MEG with multivariate pattern analysis, the study compared brain responses to predictable and random tone sequences during wakefulness and sleep. Feature-specific responses to subtle tone changes were present in N1 and N2 sleep, though weaker than when awake. The brain preactivated feature-specific representations during sleep, but tracking of statistical associations between tones occurred only during wakefulness. This suggests that while some automatic predictive processing of low-level features persists, higher-order anticipation of patterns is disrupted when consciousness fades.
Neural activity in primary sensory regions not directly relevant to a task can predict conscious perception of near-threshold stimulation in a different sensory modality. Using magnetoencephalography and multivariate decoding analysis across tactile, visual, and auditory tasks, supramodal spatiotemporal patterns were identified that predicted conscious perception. These patterns included activity in visual cortex predicting conscious perception of auditory stimuli. The findings were replicated in a control experiment and were independent of the type of report (button press or withholding a button press). The results suggest a common signature of conscious access across sensory modalities, involving temporally late and widespread broadcasting of neural representations.