Impairments of Gestalt perception in the intact hemifield of hemianopic patients are reflected in gamma-band EEG activity

Schadow, Jeanette and Dettler, Nicole and Paramei, Galina V. and Frund, ingo and Sabel, Bernhard A. and Herrmann, Christoph S. (2009) Impairments of Gestalt perception in the intact hemifield of hemianopic patients are reflected in gamma-band EEG activity. Neuropsychologia, 47 (5). pp. 556-568. ISSN 0028-3932

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Abstract

Gamma-band responses (GBRs) are associated with Gestalt perception processes. In the present EEG study, we investigated the effects of perceptual grouping on the visual GBR in the perimetrically intact visual field of patients with homonymous hemianopia and compared them to healthy participants. All observers were presented either random arrays of Gabor elements or arrays with an embedded circular arrangement. For the hemianopic patients, the circle was presented in their intact hemifield only. For controls, the hemifield for the circle presentation was counterbalanced across subjects. The participants were instructed to detect the circle by pressing a corresponding button. A wavelet transform based on Morlet wavelets was employed for the calculation of oscillatory GBRs. The early evoked GBR exhibited a larger amplitude and shorter latency for the healthy group compared to hemianopic patients and was associated with behavioral measures. The late total GBR between 200 and 400 ms after stimulus onset was significantly increased for Gestalt-like patterns in healthy participants. This effect was not manifested in patients. The present findings indicate deficits in the early and late visual processing of Gestalt patterns even in the intact hemifield of hemianopic patients compared to healthy participants.

Item Type: Article
Keywords: ERPs; Gamma-band oscillations; Grouping; Impaired contour integration ERPs; Gamma-band oscillations; Grouping; Impaired contour integration
Subjects: B Philosophy. Psychology. Religion > BF Psychology
Faculty / Department: Faculty of Science > Psychology
Depositing User: Users 3 not found.
Date Deposited: 05 Mar 2014 15:37
Last Modified: 18 Apr 2016 08:54
URI: http://hira.hope.ac.uk/id/eprint/212

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