Effects of brain polarization on reaction times and pinch force in chronic stroke

Anodal tDCS shortened reaction times and improved pinch force in the paretic hand relative to Sham stimulation, an effect present in patients with higher impairment.tDCS of M1affected hemisphere can modulate performance of motor tasks simpler than those previously studied, a finding that could potentially benefit patients with relatively higher impairment levels.Rehabilitative treatments result in incomplete motor recovery after stroke. Six months after stroke, 65 percent of survivors cannot use their paretic hand into daily living activities to the extent done before [1-5]. Absence or minimal hand movements by four weeks is predictive of poor motor outcome [6] and only a small percentage of patients recover function to the extent of community-matched healthy subjects [7] resulting in marked difficulties in carrying out activities of daily living (ADL).Recent studies demonstrated that enhancing activity in motor areas of the affected hemisphere (M1affected hemisphere) by means of anodal transcranial DC stimulation (tDCS) [8-10] or repetitive transcranial magnetic stimulation (rTMS) [11] results in improvements in performance of complex ADL-like tasks with the paretic hand [12]. The tasks utilized in these studies, including the Jebsen-Taylor test (JTT), are cognitively demanding, only in part preprogrammed, and require complex online updating of sensory information as well as adequate sensorimotor integration for accurate performance [13]. Successful performance of the JTT requires a complex pattern of activation of muscles and joints as well as the use of targets and tools [13] and such skilled movements engage an extensive network of brain regions [14-16]. As a consequence, ADL-like tasks included in the JTT can be fully carried out by a minority of stroke patients [6].At present, it is not known if the beneficial effects of tDCS apply only to complex motor tasks in patients with reduced impairment, capable of performing ADL-like tasks or if it can also benefit pe