Neural correlates of visual ambiguity and meta-perceptual confidence rating

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The information available to our senses is incomplete and ambiguous. Our perceptual system normally integrates this the bottom-up sensory information with top-down perceptual memories in order to resolve this ambiguity and to construct stable and reliable percepts. During observation of an ambiguous figure our perception becomes unstable and alternates between two equally probable but mutual exclusive interpretations. We recently found two ERP components (P200 and P400) with small vs. large amplitudes evoked by ambiguous figures vs. disambiguated figure variants (ERP Ambiguity Effects). These unusually strong effects generalize across very different visual categories and complexity levels (motion, semantics, emotional face expressions and letters/numbers). A recent study with Necker cube stimuli revealed perfect confirmation of a predictive coding model about perceptual processing. The model indicates that the P200 correlates with top-down contributions to the perceptual process. The P400 seems to reflect the integration of bottom-up and top-down elements and thus the reliability of the perceptual outcome. These findings and the introduced model are the starting point of this grant proposal consisting of three projects:Project A: Testing for generalizability across visual categories and complexity levelsSo far, the relation between the ERP Ambiguity Effects and the predictive coding model has only been shown for Necker cube stimuli. We plan to test whether these model-conform findings generalize across other stimulus categories and complexity levels mentioned above.Project B: Test for ERP Ambiguity Effects alterations in SSD PatientsPatients with schizophrenia spectrum disorder (SSD) show deficits in integrating bottom-up sensory with top-down information. We plan to test whether this integration deficit is reflected in a deviated pattern of ERP Ambiguity Effects. Project C: Testing for generalizability of the ERP Ambiguity Effects concerning neural sourcesThe spatial locations of the ERP Ambiguity Effects are so far based on EEG voltage maps. The aims of this subproject are, using concurrent EEG/fMRI recordings: (1) To specify whether similar ERP scalp distributions across different stimulus categories and complexity levels are based on the same underlying neural sources, as predicted by the model. (2) To identify brain areas underlying perceptual disambiguation processes and respective differences between SSD patients and controls. The results of this project at the interface between neurobiology, psychology of perception and psychiatry may advance the understanding of the neural and functional features of the ERP Ambiguity Effects and predictive coding approaches to perception. Given the large sizes of the ERP Ambiguity Effects, the results from the current project may have a good prospect for future clinical applications.