Behavioral and neurological effects of tDCS on speech motor recovery: A single-subject intervention study

This paper reports a feasibility study designed to evaluate the behavioral and neurological effects of using transcranial direct current stimulation (tDCS) in conjunction with speech motor learning treatment for individuals with acquired speech impairment subsequent to stroke. Most of the research using tDCS to enhance treatment outcomes in stroke recovery has focused on either limb motor control or aphasia treatment. Using a multiple-baseline multiple-probe crossover design, we compared both behavioral and brain connectivity-based outcomes following speech motor learning treatment with both Active tDCS and Sham tDCS. We observed that both treatment phases led to improvement in short-term maintenance, but that Active tDCS was associated with greater long-term maintenance improvement. Active tDCS was also associated with an increase in functional connectivity in the left hemisphere and interhemispherically in an ROI-based network analysis examining correlations among areas associated with speech production and acquired speech impairment. This report supports the possibility that tDCS may enhance both behavioral and neurological outcomes and indicates the importance of additional work in this area, although replication is required to confirm the extent and consistency of tDCS benefits on speech motor learning treatment outcomes.