Visual masking with frontally applied pre-stimulus TMS and its subject-specific neural correlates

Dynamic Interactions between Top-Down Expectations and Conscious Awareness

It is well known that top-down expectations affect perceptual processes. Yet, remarkably little is known about the relationship between expectations and conscious awareness. We address three crucial outstanding questions: (1) how do expectations affect the likelihood of conscious stimulus perception?; (2) does the brain register violations of expectations nonconsciously?; and (3) do expectations need to be conscious to influence perceptual decisions? Using human participants, we performed three experiments in which we manipulated stimulus predictability within the attentional blink paradigm, while combining visual psychophysics with electrophysiological recordings. We found that valid stimulus expectations increase the likelihood of conscious access of stimuli. Furthermore, our findings suggest a clear dissociation in the interaction between expectations and consciousness: conscious awareness seems crucial for the implementation of top-down expectations, but not for the generation of bottom-up stimulus-evoked prediction errors. These results constrain and update influential theories about the role of consciousness in the predictive brain.SIGNIFICANCE STATEMENT While the relationship between expectations and conscious awareness plays a major role in many prediction-based theories of brain functioning, thus far few empirical studies have examined this relationship. Here, we address this gap in knowledge in a set of three experiments. Our results suggest that the effect of expectations on conscious awareness varies between different steps of the hierarchy of predictive processing. While the active use of top-down expectations for perceptual decisions requires conscious awareness, prediction errors can be triggered outside of conscious awareness. These results constrain and update influential theories about the role of consciousness in the predictive brain.