Cortical processes underlying metacontrast masking across different contrast polarities

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2018

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Aydın, Alaz

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In this study a metacontrast masking experiment is conducted together with electroencephalography (EEG) recordings in order to investigate the neural mechanisms underlying visual masking phenomena. We employed a contour detection task under same and opposite target-mask contrast polarity conditions, together with varying stimulus onset asynchronies (SOA). Behavioral experiments resulted in unimodal type-A and type-B backward masking functions for opposite and same contrast polarity conditions, respectively. Relying on this difference as an indication of non-identical neural mechanisms, we collected EEG data under specific SOAs for an analysis of activation patterns under different contrast polarity masks. The behavioral results provided further evidence for sustained-transient dual-channel models of masking, specifically suggesting inhibition of on-sustained activity by off-transient activity, in accordance with previous research (Breitmeyer, 1978). Moreover, EEG analysis revealed significant differences in evoked potentials due to a change in mask contrast polarity at a short SOA of 10 ms, and compared polarity effects at two other critical SOA values of 50 ms and 200 ms.

Subject Keywords

Neurosciences., Visual masking., Visual perception., Electroencephalography.

URI

http://etd.lib.metu.edu.tr/upload/12622680/index.pdf
https://hdl.handle.net/11511/27508

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Graduate School of Informatics, Thesis

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Citation Formats

A. Aydın, “Cortical processes underlying metacontrast masking across different contrast polarities,” M.S. - Master of Science, Middle East Technical University, 2018.