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

Evoked potentials to laterally presented stimuli were collected from left and right tempero-parietal sites during performance of two visual half-field tasks, lexical decision, and line orientation discrimination. Reaction time and accuracy data were simultaneously collected. The behavioral data indicated the development of a right field advantage for the lexical decision task as a function of practice. A principal components analysis revealed three independent evoked potential components which displayed task-dependent hemispheric asymmetries. Multiple regression analyses revealed that visual half-field asymmetries in response accuracy were closely related to hemispheric asymmetries on several independent evoked response components. Subject's scores on independent tests of verbal reasoning and spatial relations were also found to be closely related to hemispheric asymmetry on several independent evoked response components. These data support a multidimensional concept of cerebral specialization. They also suggest that visual field asymmetries reflect the confluence of several underlying processes which have independent lateralization distributions across the population. In general, the results underscore the need for further research on the nature of the relationship between cerebral and perceptual asymmetries.