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Language rehabilitation in bilingual aphasia: A tDCS study

Poster D5 in Poster Session D with Social Hour, Friday, October 7, 5:30 - 7:15 pm EDT, Millennium Hall

Katy Borodkin¹, Yarden Ashkenazi¹, Maria Gurkov¹, Goni Broid¹, Liora Chernovilski¹; ¹Tel Aviv University

Background: Numerous behavioral therapies have been suggested to reduce naming difficulties in persons with chronic aphasia; however, their effectiveness is somewhat limited. To improve the outcomes, researchers have been applying neuromodulation techniques (e.g., transcranial direct current stimulation, tDCS) as an adjunct to the conventional language therapy. While previous research has been conducted exclusively in monolinguals, the current study focused on bilingual speakers with aphasia. The effects of naming therapy combined with tDCS were assessed on naming the trained items as well as on generalization to untrained items and to connected speech in the treated language. We also tested for cross-language transfer of therapy benefits to naming and connected speech in the untreated language. Method: Eight participants (four women) were enrolled in the study thus far. They were aged 68 years on average (range: 46 to 80 years) and have had chronic aphasia for 9 to 36 months resulting from a single vascular stroke in the left hemisphere. Participants were Russian native speakers who learned Hebrew as a second language later in life (age range: 23 to 45 years) and used it in everyday life prior to the stroke. Ten 1-hour therapy sessions were divided equally between two blocks, each lasted two weeks. Therapy targeted word retrieval in Hebrew. In one of the blocks, active stimulation was delivered (20 min, 2 mA), and the other served as a control condition (sham stimulation). The anode electrode was placed over the left dorsolateral prefrontal cortex and the cathode electrode – over the right supraorbital area. Before and after each block, naming of trained and untrained items as well as connected speech (elicited by a picture sequence) in Hebrew, the treated language, and Russian, the untreated language, were assessed. Results: Change scores were calculated as the difference between the scores after and before therapy. Difference between the change scores of the two blocks was tested using one-tailed paired-samples t-test. Naming the trained and untrained items in Hebrew improved comparably following the active and the sham block (trained: 44% vs 38%, respectively; untrained: 8% vs 2%, respectively). In contrast, naming translation equivalents in Russian of the trained and untrained words in Hebrew improved significantly more following active stimulation compared to sham stimulation (trained: 12% vs 0.5%, respectively; untrained: 7% vs -3%). Finally, there was a greater increase in productivity of connected speech (i.e., words per minute, different words per minute) in the active than sham block in both Hebrew and Russian (the differences were marginally significant, p < .10). The blocks did not differ in other indices of connected speech (i.e., word retrieval difficulties, dysfluency, and informativeness) in either language. Conclusions: Anodal tDCS combined with naming therapy may have numerous benefits in bilingual speakers with aphasia: It promotes generalization to connected speech in the treated language and to naming and connected speech in the untreated language. These preliminary results highlight the clinical applicability of tDCS in bilingual speakers with aphasia and pave the way to developing diagnostic and therapy protocols specifically designed for this population.

Topic Areas: Disorders: Acquired, Language Therapy