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Enhancing Prefrontal Theta Activity Associated with Action Verbal Fluency in Parkinson’s Disease
Poster Session C, Saturday, September 13, 11:00 am - 12:30 pm, Field House
Karim Johari1, Fatemeh Tabari1; 1Louisiana State University
Word retrieval deficits often present in patients with Parkinson’s disease (PD). While invasive brain stimulation of subcortical structures improves motor symptoms in Parkinson’s disease (PD), its effects on speech and language impairments in PD remain inconsistent. Therefore, it is crucial to develop novel brain protocols that could improve word findings deficits in PD. Accumulating evidence supports the application of transcranial alternating current stimulation (tACS) to improve motor and non-motor deficits in PD. We employed a sham-controlled non-invasive neurostimulation protocol that aimed to examine the effect of multisite 4 Hz HD-tACS over the left frontal aslant tract (FAT) on verb fluency performance in individuals with PD. FAT Connects inferior frontal gyrus (IFG) to supplementary motor area (SMA) and play crucial role in speech and language. Abnormal activity has been shown in both IFG and SMA in individual with PD. Seventeen non-demented PD participated in this study. They were native speaker of English and had normal or corrected vision. They received actual and sham stimulations with a week apart. The order of sessions was counterbalanced across participants. Following actual and sham stimulations, EEG data were recorded while participants performed action fluency (AF), phonemic fluency (PF), and semantic fluency (SF) tasks. Patients generated significantly fewer items in AF compared to PF and SF, regardless of stimulation, suggesting a relative decline in action word retrieval in PD. Relative to sham, the power of prefrontal theta activity significantly increased following actual stimulation for AF; this effect was not observed for PF and SF. Moreover, AF elicited a significant increase in prefrontal theta activity relative to PF and SF following actual stimulation but not sham stimulation. Based on these findings, we propose that stimulation of the left FAT in PD modulates oscillatory markers of word retrieval for motion-related words (i.e., action fluency). This selective modulation of prefrontal theta activity does not indicate a general improvement in cognitive control but rather suggests that stimulation specifically enhances the executive control required for action word retrieval in PD. These results suggest that 4 Hz stimulation of the FAT may serve as a non-invasive protocol to improve action semantics, which is typically compromised in PD.
Topic Areas: Language Production, Speech Motor Control