The Effect of Anterior Cingulate Cortex Direct Current Stimulation on Speech Monitoring Ability in Individuals with Aphasia: A Randomized, Double-Blinded Study

[Background]Aphasia is characterized by language comprehension and production deficits and it also reduces the ability to spontaneously monitor speech errors. Recent concepts stress the role of medial frontal areas, especially the anterior cingulate cortex (ACC) in self-monitoring of speech. The current study mainly aimed at examining the effect of transcranial direct current stimulation (tDCS) over the ACC on speech monitoring abilities in individuals with aphasia.[Methods]A randomized, sham-controlled, double-blind, within-subject study was designed to explore the involvement of ACC in individuals with non-fluent aphasia. Participants will be 20 patients with a left unilateral stroke for at least six months post onset of lesion classified as aphasic based on brain imaging reports, neurological exams, and the results of a Persian aphasia screening test. They are expected to be fluent in Farsi speaking before the stroke and be able to produce single words now. During four separate sessions, participants will perform four 108-item picture naming tasks in either the normal or noised-masked auditory conditions during anodal (20 minutes, 2 mA) or sham tDCS over the ACC. The interval between sessions will be at least seven days. Performance accuracy and the amount of self-monitoring behaviors will serve as primary outcome measures.[Discussion]This will be the first study which explores the effects of tDCS over the ACC on the ability of individuals with aphasia to detect and repair error responses in both overt and inner speech situations. Results will be discussed in relation to recent self-monitoring concepts in speech production and available data about monitoring skills in aphasia.