Cerebral lateralization in random letter task in the visual modality: a transcranial Doppler study.

Seven right handed volunteers were studied to determine cerebral lateralization patterns for a visually presented random letter task. The subjects participated in three conditions, which included resting baseline, passive fixation (nonlinguistic), and random letter (linguistic) tasks. Mean blood flow velocity (MBFV) was recorded using bilateral simultaneous transcranial Doppler measurements in the posterior cerebral arteries in these conditions. The experimental conditions produced an increase in MBFV during both tasks but the linguistic task showed a greater change. There was a tendency toward right lateralization with the linguistic compared to the nonlinguistic tasks. There is a physiological correlate of right hemisphere participation in the processing of the random letter task.