Orientation-based texture segmentation in strabismic amblyopia

Texture segmentation of 'target' Gabors from an array of 'background' Gabor s was measured in terms of the difference in orientation between the two re gions, as well as the difference in orientation within each region. Segment ation was shown to occur on the basis of local orientation differences at t he boundary between the target and background regions (Nothdurft, H.C. (199 2). Feature analysis and the role of similarity in preattentive vision. Per ception and Psychophysics, 52, 355-375.). We obtained similar results for b oth the amblyopic and non-amblyopic eye of three strabismic amblyopes, and showed also that the effects of texture undersampling and positional jitter were similar for the two eyes. This pattern of results is consistent with intact mechanisms of texture perception in amblyopic cortex, and suggests a lso that any amblyopic deficits in first-order cortical units (undersamplin g and/or positional uncertainty) do not limit higher-order texture segmenta tion processes. Therefore, first- and second-order processes involved in pe rceptual grouping of oriented elements (that appear to be abnormal in ambly opic cortex; Kovacs, I., Polat, U., Norcia, A.M. (1996). Breakdown of bindi ng mechanisms in amblyopia. Association for. Research in Vision and Ophthal mology Abstracts; Mussap, A.J., Levi, D.M. (1995). Amblyopic deficits in pe rception of second-order orientation. Investigative Ophthalmology and Visua l Science (Supplement), 36, S634; Mussap, A.J., Levi, D.M. (1998). Amblyopi c deficits in perceptual grouping. Vision Reseal ch, submitted) do not cont ribute to texture perception based on orientation contrast. (C) 1998 Elsevi er Science Ltd. All rights reserved.