It is known that weak
transcranial direct current stimulation (
tDCS) induces persistent excitability changes in the cerebral cortex. There are, however, few studies that compare the after-effects of anodal versus cathodal
tDCS in patients with
stroke. This study assessed the after-effects of
tDCS over the motor cortex in patients with hemiparetic
stroke and healthy volunteers. Seven
stroke patients and nine healthy volunteers were recruited. Ten minutes of anodal and cathodal
tDCS (1 mA) and
sham stimulation were applied to the affected primary motor cortex (M1) on different days. In healthy subjects,
tDCS was applied to the right M1. Before and after
tDCS, motor-evoked potentials (MEPs) in the first dorsal interosseous (FDI) muscle and silent period were measured. Anodal
tDCS increased the MEPs of the affected FDI in patients with
stroke as well as in healthy subjects. Cathodal
tDCS increased the MEPs of the affected FDI in patients with
stroke. In healthy subjects, however, cathodal
tDCS decreased the MEPs. We found no significant change in the duration of the silent period after anodal or cathodal
tDCS. We found that both anodal and cathodal
tDCS increased the affected M1 excitability in patients with
stroke. It is thought that the after-effects of
tDCS are different in patients with
stroke compared with healthy subjects.