LATERALIZED CORTICAL ACTIVITY DUE TO PREPARATION OF SACCADES AND FINGER MOVEMENTS - A COMPARATIVE-STUDY

The topography and time course of event-related asymmetries of the EEG associated with horizontal saccadic eye movements and finger movement s was compared in a 4-choice response task, where the subjects had to respond to the imperative stimulus (S2) by moving the right or left in dex finger or by making a saccade to the right or the left. The cue st imulus (S1) contained full, partial, or no information about the direc tion and the effector. In case of finger movements 3 distinct laterali sations were found: (I) increased negativity over the motor cortex con tralateral to the future movement direction, (2) increased contralater al negativity at temporoparietal sites beginning 200 ms after delivery of the directional information, and (3) increased ipsilateral negativ ity at temporo-parietal sites beginning 350-500 ms after delivered dir ection and effector information. The early temporo-parietal lateralisa tion was also visible in case of saccadic eye movements and in case of effector-unspecific directional information. Before saccadic eye move ments no other distinct lateralisation could be observed at any record ing site. In sum, lateralised cortical activities due to preparation p rocesses for finger movements and due to effector-unspecific processin g of directional Information for motor preparation by the posterior pa rietal cortex could be demonstrated. whereas no distinct lateralisatio n due to preparation for saccadic eye movements was visible. (C) 1997 Elsevier Science Ireland Ltd.