Abstract EN:

A huge amount of studies have shown that dyslexic individuals exhibit poor performance in visual perceptual, oculomotor and visual attentional tasks which, according to many researchers, reflect an impairment of the magnocellular pathway. Our work evaluates the link between the visual attention span (VA span), eye movements and the magnocellular pathway in both dyslexic and typically developing children. In accordance with the multitrace memory model's predictions, results show that the VA span is associated with fixation number in reading, independently of the participants' phonological skills. In contrast, no relation was found between the VA span and eye movements in visual search. Saccadic latencies of those dyslexic children with a VA span deficit differ from those of normal-readers and of dyslexic children without VA span disorder on a prosaccade task including Gap and Overlap conditions. Finally, the VA span deficit was not found to be associated with a lower sensibility to phantom contours. The present findings allow proposing an alternative account of the different eye movement patterns observed in dyslexic children during reading and visual search. They suggest a VA span disorder as contributing to the atypical eye movements found in reading. They further show that the VA span reduction is associated with neither visual perceptual or basic oculomotor deficits, nor single letter identification difficulties. The VA span reduction seems related to subtle but abnormal repartition of visual attention. We found no evidence for an associated disorder of the visual magnocellular pathway. Our findings further speak for the necessity to take into account the heterogeneity of the cognitive profiles in developmental dyslexia.