Cognitive skills and their underlying brain organization are not fixed but can be shaped by the experience of the individual. The extent of such experience-dependent plasticity provides valuable information about the ability of the nervous system to reorganize and adapt. To this aim, we have been studying individuals who are born deaf. The goal of our research is to document the effect of deafness and that of American Sign Language (ASL-the visuo-manual language used by the deaf) on vision and its neural organization. Our working hypothesis is that deafness alters visuo-spatial attention. Building on our previous behavioral and brain imaging work, we will test the hypothesis that deafness leads to enhanced peripheral visual attention, and we will characterize the consequences of this peripheral enhancement for the processing of centrally presented visual information. Attention is a multi-faceted concept and we will be interested in asking which other aspects of visual attention, beyond its spatial distribution, may be modified by early deafness. It may be that cross-modal plasticity proceeds primarily by reshaping the brain systems that typically support multimodal integration. Under this view, we expect little to no changes in other aspects of attention beyond spatial attention for which cross-modal links are well established. In contrast, the alternate view predicts that compensatory plasticity enhances many aspects of the remaining modalities, with deaf individuals possibly displaying enhancement on a wide range of visual and attentional skills. Deaf and hearing adults will be compared first;then, children (7-17 years old) will be included so as to characterize the effects of altered experience on the developmental trajectory of the skill under study. These studies will first contrast deaf signers and hearing non-signers to establish a population difference. Deaf non-signers and hearing signers will then be tested to separately assess the contributions of deafness and ASL use in the changes observed. This is important as deafness and ASL use have been documented to have different effects on visual skills. This work will allow us to document the range of plastic behaviors exhibited by the visual system as well as boundary conditions on this plasticity. In addition, it will provide insights for the development of environments better suited to deaf individuals'needs.
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