Prior Expectation Modulates Repetition Suppression without Perceptual Awareness

Area of Science:

• Neuroscience
• Cognitive Psychology
• Perception

Background:

• Repetition suppression (RS) is a decrease in brain response to repeated stimuli.
• Traditionally attributed to bottom-up neuronal adaptation.
• Emerging evidence suggests top-down predictive mechanisms drive RS, but their reliance on conscious strategies is debated.

Purpose of the Study:

• To investigate whether top-down predictive mechanisms of RS operate independently of conscious awareness.
• To determine if repetition probability influences RS even when stimuli are not consciously perceived.
• To differentiate automatic versus strategy-dependent top-down influences on RS.

Main Methods:

• Utilized an unconscious priming paradigm combined with electroencephalography (EEG) recordings.
• Manipulated the probability of stimulus repetition.
• Measured behavioral priming and EEG responses, including theta-band power as an index of conflict detection.

Main Results:

• Behavioral priming and RS in occipital areas were modulated by repetition probability, irrespective of prime awareness.
• This finding challenges the notion that RS modulation is solely a byproduct of conscious strategies.
• Theta-band power increases (conflict detection) were modulated only by expectations during conscious priming, indicating a role for conscious strategies.

Conclusions:

• Top-down influences on repetition suppression can be automatic, occurring in sensory brain regions without conscious awareness.
• Conscious strategies are implicated in conflict detection associated with repetition suppression, particularly when expectations are consciously processed.
• The predictive mechanisms underlying RS exhibit both automatic and strategy-dependent components.