Detection and categorization abilities following peripheral or cerebral visual impairment

Abstract

Literature data suggest that cortical reorganization can occur following peripheral as well as cerebral visual system damage. Nevertheless, visual processing adaptation to either type of damage remains unclear especially in respect to the central visual field (often partly preserved). To better apprehend visual processing in such damages, 8 optic neuritis patients remitted for one month (4 right and 4 left optic neuritis) and 8 patients with homonymous hemianopia (4 right hemianopes and 4 left hemianopes, following a contralateral occipital damage) completed a detection and a categorization task of natural scenes images. They were compared respectively to 16 young and 16 aged healthy controls. Filtered (in high or low spatial frequencies) and unfiltered images were briefly presented centrally on a computer screen. Participants were required to respond when a natural scene was presented (detection task) or to indicate if the stimulus was a city or a highway (categorization task). Accuracy (error rate) and response times (RT) were recorded. In remitted optic neuritis patients, altered performance was observed with the (previously) pathologic eye (either right or left) compared to their healthy eye or to the young control group. The deficit seemed specific to low spatial frequencies (accuracy) and stronger in the categorization than in the detection task (RT). In hemianopes, although accuracy was not altered in either task or patients groups, left hemianopes showed longer RT in both tasks (regardless the spatial frequency condition) whereas right hemianopes only tended to show longer RT for high spatial frequency in the categorization task (compared to aged controls). Overall our results suggest that central vision is not preserved following either a peripheral or a cerebral visual impairment and that the nature of this deficit depends on the lesion side only for cortical damage, consistent with the anatomical and functional organization of the visual system.

The Edmond and Benjamin de Rothschild Foundations (Geneva and New York).