Using transcranial direct-current stimulation to treat stroke patients with aphasia

Abstract

Background and purpose: Recent research suggests that increased left hemisphere cortical activity, primarily of the left frontal cortex, is associated with improved naming performance in stroke patients with aphasia. Our aim was to determine whether anodal transcranial direct-current stimulation (tDCS), a method thought to increase cortical excitability, would improve naming accuracy in stroke patients with aphasia when applied to the scalp overlying the left frontal cortex.

Methods: Ten patients with chronic stroke-induced aphasia received 5 days of anodal tDCS (1 mA for 20 minutes) and 5 days of sham tDCS (for 20 minutes, order randomized) while performing a computerized anomia treatment. tDCS positioning was guided by a priori functional magnetic resonance imaging results for each individual during an overt naming task to ensure that the active electrode was placed over structurally intact cortex.

Results: Results revealed significantly improved naming accuracy of treated items (F[1,9]=5.72, P<0.040) after anodal tDCS compared with sham tDCS. Patients who demonstrated the most improvement were those with perilesional areas closest to the stimulation site. Crucially, this treatment effect persisted at least 1 week after treatment.

Conclusions: Our findings suggest that anodal tDCS over the left frontal cortex can lead to enhanced naming accuracy in stroke patients with aphasia and, if proved to be effective in larger studies, may provide a supplementary treatment approach for anomia.

Figure 1

Example of the treatment set-up. Patients trained on a computerized picture-word matching task (a) while receiving transcranial direct current stimulation (tDCS). During both anodal tDCS and sham tDCS treatment phases, the anode electrode (b) was placed over the pre-designated area on the scalp overlying the left frontal cortex, while the reference cathode electrode (c) was placed over the right shoulder. The constant current stimulator (d) was placed out of the patients’ sight behind a partition.