The purpose of this study is to determine whether the effect of treatment for acquired speech impairment can be enhanced by combining effective behavioral treatment with non-invasive brain stimulation. Transcranial direct current stimulation (tDCS), which delivers low-intensity current to the scalp, and is a safe and well-tolerated approach that poses a non-significant risk to participants. tDCS provides low intensity neural stimulation which has been shown to facilitate motor learning in other domains of stroke rehabilitation such as arm motor learning but the potential to enhance speech motor learning has not been explored. This will be examined with a series of single-case experimental designs.