Neural responses to reflection symmetry for shapes defined by binocular disparity, and for shapes perceived as regions of background

Karakashevska, Elena, Rampone, Giulia, Tyson-Carr, John ORCID: 0000-0003-3364-2184, Makin, Alexis DJ ORCID: 0000-0002-4490-7400 and Bertamini, Marco ORCID: 0000-0001-8617-6864 (2021) Neural responses to reflection symmetry for shapes defined by binocular disparity, and for shapes perceived as regions of background NEUROPSYCHOLOGIA, 163. 108064-. ISSN 0028-3932, 1873-3514

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Abstract

Human perception of symmetry is associated with activation in an extended network of extrastriate visual areas. This activation generates an ERP called the Sustained Posterior Negativity (SPN). In most studies so far, the stimuli have been defined by luminance. We tested whether the SPN is present when stimuli are defined by stereoscopic disparity using random dot stereograms (RDS). In Experiment 1, we compared the SPN signal for contours specified by binocular disparity and contours specified by monocular cues. The SPN was equivalent, suggesting that the type of contour does not alter the SPN signal. In Experiment 2 we exploited the unique property of RDS to provide unambiguous figure-ground arrangements. Psychophysical work has shown that symmetry is more easily detected when it is a property of a single object (i.e., within a figure), compared to a property of a gap between two objects (i.e., the ground). Therefore, the target regions in this experiment could either be foreground or background. The SPN onset was delayed when the symmetry was in a ground region. This may be because object formation interferes with the processing of shape information in the ground region.

Item Type:	Article
Uncontrolled Keywords:	Symmetry, EEG, Perception, Stereopsis, SPN, Depth perception
Divisions:	Faculty of Health & Life Sciences Faculty of Health & Life Sciences > Inst. Population Health
Depositing User:	Symplectic Admin
Date Deposited:	02 Nov 2021 16:45
Last Modified:	16 Jun 2026 11:35
DOI:	10.1016/j.neuropsychologia.2021.108064
Open Access URL:	https://doi.org/10.1016/j.neuropsychologia.2021.10...
Related Websites:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3142545
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