title: Identification of contrast-defined letters benefits from perceptual learning in adults with amblyopia.
abstract: Amblyopes show specific deficits in processing second-order spatial information (e.g. Wong, Levi, & McGraw (2001). Is second-order spatial loss in amblyopia explained by the loss of first-order spatial input? Vision Research, 41, 2951-2960). Recent work suggests there is a significant degree of plasticity in the visual pathway that processes first-order spatial information in adults with amblyopia. In this study, we asked whether or not there is similar plasticity in the ability to process second-order spatial information in adults with amblyopia. Ten adult observers with amblyopia (five strabismic, four anisometropic and one mixed) were trained to identify contrast-defined (second-order) letters using their amblyopic eyes. Before and after training, we determined observers' contrast thresholds for identifying luminance-defined (first-order) and contrast-defined letters, separately for the non-amblyopic and amblyopic eyes. Following training, eight of the 10 observers showed a significant reduction in contrast thresholds for identifying contrast-defined letters with the amblyopic eye. Five of these observers also showed a partial transfer of improvement to their fellow untrained non-amblyopic eye for identifying contrast-defined letters. There was a small but statistically significant transfer to the untrained task of identifying luminance-defined letters in the same trained eye. Similar to first-order spatial tasks, adults with amblyopia benefit from perceptual learning for identifying contrast-defined letters in their amblyopic eyes, suggesting a sizeable degree of plasticity in the visual pathway for processing second-order spatial information.
authors.affiliation: College of Optometry and Center for Neuro-Engineering and Cognitive Science, University of Houston, Houston, TX, USA. schung@optometry.uh.edu
authors.forename: Susana T L
authors.initials: ST
authors.lastname: Chung
authors.forename: Roger W
authors.initials: RW
authors.lastname: Li
authors.forename: Dennis M
authors.initials: DM
authors.lastname: Levi
mesh_terms: D000221:Adaptation, Ocular / Q000502:physiology; D000328:Adult; D000550:Amblyopia / Q000503:physiopathology*; D015858:Anisometropia / Q000503:physiopathology; D015350:Contrast Sensitivity / Q000502:physiology; D005260:Female; D006801:Humans; D007858:Learning / Q000502:physiology; D008027:Light; D008297:Male; D008875:Middle Aged; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D011578:Psycholinguistics; D011601:Psychophysics; D012684:Sensory Thresholds / Q000502:physiology; D013285:Strabismus / Q000503:physiopathology; D014792:Visual Acuity / Q000502:physiology