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Titolo:
Deficit of visual contour integration in dyslexia
Autore:
Simmers, AJ; Bex, PJ;
Indirizzi:
Univ Coll London, Inst Ophthalmol, Dept Visual Rehabil, London EC1V 9EL, England Univ Coll London London England EC1V 9EL habil, London EC1V 9EL, England
Titolo Testata:
INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE
fascicolo: 11, volume: 42, anno: 2001,
pagine: 2737 - 2742
SICI:
0146-0404(200110)42:11<2737:DOVCII>2.0.ZU;2-C
Fonte:
ISI
Lingua:
ENG
Soggetto:
SPATIAL-FREQUENCY; MOTION DETECTION; ORGANIZATION; AMBLYOPIA; CONTRAST; FIELD; UNCERTAINTY; CHILDREN; STIMULI; CORTEX;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
49
Recensione:
Indirizzi per estratti:
Indirizzo: Simmers, AJ Univ Coll London, Inst Ophthalmol, Dept Visual Rehabil, 11-43 Bath St, London EC1V 9EL, England Univ Coll London 11-43 Bath St London England EC1V 9EL ngland
Citazione:
A.J. Simmers e P.J. Bex, "Deficit of visual contour integration in dyslexia", INV OPHTH V, 42(11), 2001, pp. 2737-2742

Abstract

PURPOSE. The visual processing of text occurs spontaneously in most readers, Dyslexic persons, however, often report both somatic symptoms and perceptual distortions when trying to read. It is possible that the perceptual distortions experienced by those with dyslexia reflect a disturbance in the basic mechanisms supporting perceptual organization at the early stages of visual processing. Integration of information over extended areas of visual space can be measured psychophysically in a task that requires the detection of a path defined by aligned, spatially narrow-band elements on a dense field of otherwise similar elements that are randomly oriented and positioned. In the present study a contour integration task was used to investigate such perceptual organization in dyslexia. METHODS. The detection of contours or paths composed of Gabor micropatterns was performed within a field of randomly oriented distracter elements in a 2-alternate forced choice (AFC) task. The stimuli were manipulated by randomly varying both the density of the background noise elements and the number of elements that defined a path of constant length. RESULTS. In all observers, sensitivity to the paths increased with the number of target elements comprising the path, and subjects in both groups exhibited similar trends in relative density of the stimuli. However, in all conditions, dyslexic observers were two to three times less sensitive to path stimuli than the control group. CONCLUSIONS. In the present study the authors have described a visual deficit in a global integration task in dyslexia. The pattern of deficits reported suggest that abnormal cooperative associations may be present in dyslexia that are indicative of poor perceptual integration.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 03/04/20 alle ore 14:22:01