Effects of Transcranial Direct Current Stimulation (tDCS) on Language

Aphasia is a disturbance of language, primarily caused by brain injury to the left cerebral hemisphere. Aphasia treatments include speech and language therapy and pharmacologic therapy, but several studies have found that these treatments are not completely effective for patients with aphasia, leaving them with residual deficits that significantly add to the cost of stroke-related care. Additionally, the amount and frequency of speech and language therapy delivered may have a critical effect on recovery. Therefore, there is a need for new treatments or adjuncts to existing treatments, such as brain stimulation interventions, that have the potential to show greater improvements in patients with aphasia. One such new approach for non-invasive brain stimulation is transcranial direct current stimulation (tDCS).

This study will examine the effects of tDCS during speech therapy to further examine which method or methods is best for patient recovery. Patients enrolled in the study will undergo language testing that covers a broad range of language functions. Functional Magnetic Resonance Imaging (fMRI) will be completed before and after speech therapy intervention arms to investigate the neural processes affected by tDCS and speech therapy.

Study design:

Patients will be randomly assigned to one of 2 speech therapy groups in a double-blind, partial crossover design. Patients will receive one of two different speech therapy treatment interventions to focus on specific processing deficits. Participants will undergo neuropsychological evaluation and fMRI assessment before receiving targeted or active-control anodal-tDCS for 10 therapy sessions. Participants will then be re-tested using the behavioral assessment measure and fMRI before crossing over to either receive the tDCS intervention they did not already receive, within the same speech therapy arm. They will complete a behavioral assessment and fMRI at 3 months post Treatment 2 and a final behavioral assessment at 6 months post Treatment 2.

Inclusion criteria

• Patients with a language deficit from focal neurologic damage (e.g. stroke, tumor).
• Patients must be adults and have English-language fluency.
• Patients must be eligible to undergo MRI.

Exclusion criteria

• Advanced neurodegenerative disease (i.e. Stage 3 Alzheimer's disease) or neurologic disorder (e.g. idiopathic epilepsy, Parkinson's disease, ALS)
• Severe psychopathology (e.g. schizophrenia, bipolar disorder, acute major depressive episode)
• No suspected or diagnosed uncorrectable hearing or vision difficulties, or developmental disabilities (i.e. intellectual disability or learning disability).
• Contraindications to MRI such as claustrophobia, implanted electronic devices, MRI-incompatible metal in the body, extreme obesity, pregnancy, inability to lie flat, and inability to see or hear stimulus materials