Evoked potential and visual half-field evidence for task-dependent cerebral asymmetries in congenitally deaf adults.

Twelve congenitally deaf subjects participated in a visual half-field experiment under two conditions, lexical decision and line orientation discrimination. Reaction time, accuracy, and evoked potentials from left and right temporo-parietal sites were simultaneously obtained. The evoked potential data were analyzed using a principal components analysis followed by analysis of variance and multiple regression. Both the visual half-field and the evoked potential data produced evidence of task-dependent cerebral asymmetries. Individual differences in visual half-field asymmetries in accuracy and individual scores on three cognitive paper and pencil tests were strongly predicted by linear combinations of several independent hemispheric asymmetry variables derived from evoked potential component scores. The results suggest that cerebral specialization in congenitally deaf people is a complex, multidimensional phenomenon, and provide the first evidence for a direct relationship between cerebral asymmetry and cognitive performance in this population.