Thesis defense Erik Meijs (Donders series 337)

25 March 2019

Promotor: prof. dr. F. de Lange.
Co-promotor: dr. S. van Gaal (Universiteit van Amsterdam)

Conscious perception in the predictive brain

Perception is an active process: the brain tries to make sense of its environment through interpretation of incoming sensory signals. Predictive brain theories suggest that for this purpose, the brain uses its knowledge about the environment to build expectations about upcoming inputs. These expectations are thought to originate in higher-level brain regions and guide information processing in lower-level sensory regions via top-down projections. Thus far, much was unclear about how the processing of these top-down expectations was related to conscious awareness and/or attentional processes. In a series of experiments, we found that top-down expectations have a significant impact on conscious access. They have the potential to “boost” otherwise not perceived stimuli into consciousness. Preliminary evidence suggests that this boost in conscious access may relate to decisional processes in the brain. Further neuroimaging evidence suggested that while prediction errors can be generated in the absence of conscious awareness, conscious awareness may be essential for the implementation and use of at least some types of expectations. Finally, although expectations clearly affected conscious access, no evidence for a relationship between expectations and bottom-up attention was found, suggesting these are independent processes and furthermore underscoring the reflexive nature of bottom-up attention.