Abundant evidence is emerging indicating that stuttering is associated with dysfunction of the basal ganglia. One contemporary theory is that stuttering is a manifestation of basal ganglia dysfunction causing mistiming for speech motor sequencing (Alm, 2004; Alm 2005). Alm suggests that the induced fluency from external visual and auditory cues in conditions like signing, talking to the beat of a metronome, and choral reading reduce stuttering events because the external cueing causes the speech motor plan to bypass the dysfunctional internal cueing system of the basal ganglia. Alm proposes that the lateral premotor system has a key role in compensating for basal ganglia mistiming during externally-cued speech conditions. Conversely, the medial premotor system is active during internally controlled movements during which people who stutter experience dysfluencies (Alm, 2004). Testing the idea of lateral premotor system compensation during fluency inducing conditions was completed through manipulation of the premotor cortex and supplementary motor area through Transcranial Direct Current Stimulation (tDCS) during choral reading. tDCS is a non-invasive brain stimulation technique used to inhibit or excite various areas of the cortex via electrodes placed on the scalp (Wagner, Valero Cabre, & Pascal-Leone, 2007). In this single-subject design investigation, one adult who stutters and a fluent control engaged in choral reading before, during, and after real cathodal tDCS (dampening function) to the left premotor cortex and anodal stimulation (exciting function) to the right supplementary motor area during four choral reading tasks; one adult who stutters and a fluent control received sham tDCS (placebo) with the same montage and choral reading tasks to control for the placebo effect. Another participant who stutters and a fluent control engaged in choral reading during real premotor tDCS and in post-treatment. A participant who stutters and a fluent control also underwent sham stimulation. Participants who stutter exhibited stuttering in the baseline, real and sham tDCS conditions, and the return to baseline condition; thus, the working hypothesis was not supported. Participants who served as fluent controls exhibited no stuttering across any condition. This experiment revealed that stuttering occurs more frequently in choral reading than is stated in previously published work.
|Commitee:||Gentry, Betholyn, Guyette, Thomas, Lance, Dee, Moser, Dana|
|School:||University of Arkansas for Medical Sciences|
|Department:||Communication Sciences and Disorders|
|School Location:||United States -- Arkansas|
|Source:||DAI-B 78/12(E), Dissertation Abstracts International|
|Keywords:||Basal ganglia, Choral reading, Fluency, Stuttering, Transcranial, tDCS|
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