While evidence suggests that
transcranial direct current stimulation (
tDCS) may facilitate language recovery in chronic post-
stroke aphasia, individual variability in patient response to different patterns of stimulation remains largely unexplored. We sought to characterize this variability among chronic aphasic individuals, and to explore whether repeated stimulation with an individualized optimal montage could lead to persistent reduction of
aphasia severity. In a two-phase study, we first stimulated patients with four active montages (left hemispheric
anode or cathode; right hemispheric
anode or cathode) and one
sham montage (Phase 1). We examined changes in picture naming ability to address (1) variability in response to different montages among our patients, and (2) whether individual patients responded optimally to at least one montage. During Phase 2, subjects who responded in Phase 1 were randomized to receive either real-
tDCS or to receive
sham stimulation (10 days); patients who were randomized to receive
sham stimulation first were then crossed over to receive real-
tDCS (10 days). In both phases, 2 mA
tDCS was administered for 20 min per real-
tDCS sessions and patients performed a picture naming task during stimulation. Patients' language ability was re-tested after 2-weeks and 2-months following real and
sham tDCS in Phase 2. In Phase 1, despite considerable individual variability, the greatest average improvement was observed after left-cathodal stimulation. Seven out of 12 subjects responded optimally to at least one montage as demonstrated by transient improvement in picture-naming. In Phase 2,
aphasia severity improved at 2-weeks and 2-months following real-
tDCS but not
sham. Despite individual variability with respect to optimal
tDCS approach, certain montages result in consistent transient improvement in persons with chronic post-
stroke aphasia. This preliminary study supports the notion that individualized
tDCS treatment may enhance
aphasia recovery in a persistent manner.