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Ruxandra Hera, Benoit Musel, Sylvie Chokron, Cristophe Chiquet, Jean Paul Romanet, Jean Francois Le Bas, Peyrin Carole; Visual Impairments In Age-related Macular Degeneration To Process Spatial Frequencies During Natural Scene Categorization. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6518.
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Age-related macular degeneration (AMD) is characterized by a central vision loss. We explored the relationship between the retinal lesions in AMD patients and the processing of spatial frequencies in natural scene categorization. Since the lesion on the retina is central, we expected preservation of low spatial frequency (LSF) processing and the impairment of high spatial frequency (HFS) processing.
We conducted two experiments that differed in the set of scene stimuli used and their exposure duration. AMD patients and healthy age-matched participants performed categorization tasks of natural scenes (Indoors vs. Outdoors) filtered in LSF and HSF in two experiments.
Experiment 1 revealed that AMD patients made more no-responses to categorize HSF than LSF scenes, irrespective of the scene category. In addition, AMD patients had longer reaction times to categorize HSF than LSF scenes only for indoors. Healthy participants’ performance was not differentially affected by spatial frequency content of the scenes. In Experiment 2 AMD patients demonstrated the same pattern of errors than in Experiment 1. Furthermore, AMD patients had longer reaction times to categorize HSF than LSF scenes, irrespective of the scene category. Again, spatial frequency processing was equivalent for healthy participants.Retinal lesions caused by AMD induce a lack of stimulation in the visual cortex that is devoted to the processing of the central visual field. The presence of deafferented cortical tissue may suggest a reorganization of the human cortex. Using the same task in fMRI, preliminary results on one AMD patient showed a deficit in the processing of HSF linked with a hypoactivity of occipital cortex, compared with age-matched healthy participants. However, the processing of LSF was similar in AMD patient and healthy participants, at the behavioral and neurobiological levels.
The present findings point to a specific deficit in the processing of HSF information contained in photographs of natural scenes in AMD linked with a hypoactivity of occipital cortex. The processing of LSF information is relatively preserved. Moreover, the fact that the deficit is more important when categorizing HSF indoors, may lead to new perspectives for rehabilitation procedures in AMD.
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