Unmasking the perception of temporal successions

Bridge building between metacontrast masking and temporal integration and segregation processes

by Alexander Kraut
Cumulative thesis
Date of Examination:2022-12-12
Date of issue:2023-03-02
Advisor:Dr. Thorsten Albrecht
Referee:Dr. Thorsten Albrecht
Referee:Prof. Dr. Annekathrin Schacht
Persistent Address: http://dx.doi.org/10.53846/goediss-9755

 

 

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Abstract

English

Temporal and masking research share theoretical, methodological and empirical similarities indicating that they might investigate a similar aspect of our neural functioning. Nevertheless, temporal and masking mechanisms have never before been concurrently investigated which is even more surprising since each mechanism has been proposed to be relevant in the respective other field of research. The three studies of this dissertation constitute a first step towards building a bridge between the temporal and masking research. In each of our studies, we conducted a metacontrast masking experiment and asked our participants to report on each trial whether they perceived the target-mask sequence temporally integrated, temporally segregated or masked while their neural activity was continuously recorded. By contrasting the neural activity between perceptual reports, our findings demonstrate pre-stimulus theta, alpha and beta phase differences between temporally integrated and segregated percepts. While we associated theta and alpha phase differences with a bottom-up temporal mechanism in the ventral stream, we associated beta phase differences with a top-down bias that frontal brain areas exert on brain areas further down in the neural hierarchy. In addition, post-stimulus differences in the event-related potentials indicated a spatio-temporal integration mechanism to be relevant for both temporally integrated and masked percepts. Overall, our findings extend established neural correlates of temporal mechanisms to the metacontrast masking paradigm. In addition, we demonstrate the potential information gain from concurrently investigating temporal and masking mechanisms by indicating a shared mechanism for both temporal and masking phenomena.
Keywords: metacontrast masking; temporal integration and segregation; electroencephalography; magnetoencephalography; event-related potentials; pre-stimulus activity; time-frequency analysis; two-flash task; missing element task
 
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