Multimodal EEG analysis in man suggests impairment-specific changes in movement-related electric brain activity after stroke

Movement-related slow cortical potentials and eventrelated desynchronizatio n of alpha (alpha-ERD) and beta (beta-ERD) activity after self-paced volunt ary triangular finger movements were studied in 13 ischaemic supratentorial stroke patients and 10 age-matched control subjects during movement prepar ation and actual performance. The stroke patients suffered from central arm paresis (n = 8), somatosensory deficits (n = 3) or ideomotor apraxia(n = 2 ). The multimodal EEG analysis suggested impairment-specific changes in the movement-related electrical activity of the brain. The readiness potential of paretic subjects was centred more anteriorly and laterally; during move ment, they showed increased beta-ERD at left lateral frontal recording site s. Patients with somatosensory deficits showed reduced alpha-ERD and beta-E RD during both movement preparation and actual performance. Patients with i deomotor apraxia showed more lateralized frontal movement-related slow cort ical potentials during both movement preparation and performance, and reduc ed left parietal beta-ERD during movement preparation. We conclude that (i) disturbed motor efference is associated with an increased need for excitat ory drive of pyramidal cells in motor and premotor areas or an attempt to d rive movements through projections from these areas to brainstem motor syst ems during movement preparation; (ii) an undisturbed somatosensory afferenc e might contribute to the release of relevant cortical areas from their 'id ling' state when movements are prepared and performed; and (iii) apraxic pa tients have a relative lack of activity of the mesial frontal motor system and the left parietal cortex, which is believed to be part of a network sub serving ideomotor praxis.