Asymmetry of brain potentials related to sensorimotor tasks.

The present study investigates the hemispheric specificity of event-related (ERP) and slow potentials (SP) of the brain during preparation and performance of sensorimotor (haptic) tasks. Tasks were selected which have been assumed to be processed primarily by only one brain hemisphere. ERPs, SPs and spontaneous EEGs were obtained from both hemispheres (C3-C4, P3-P4) and from Fz and Cz in a constant foreperiod (6 s) paradigm. Warning and task stimuli comprised up to four tactile stimuli, applied to index and middle finger of each hand. To maximize lateralized processing, the right-hand task required counting, the left hand task pattern matching. Components of the ERP (N1, P3, SW) and of SPs show task-dependent lateral asymmetry with the larger amplitudes contralateral to the preparing and responding hand. Results confirm hemisphere-specific processing of the tactile tasks but quantification as indicated by ERP amplitudes show considerable activity in both hemispheres. The SP-distribution rather reflects task-specific preparation than general alertness or orienting.