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Poster B35, Wednesday, November 8, 3:00 – 4:15 pm, Harborview and Loch Raven Ballrooms

Transcranial Direct Current Stimulation Changes Functional Connectivity in Primary Progressive Aphasia

Bronte N. Ficek1, Zeyi Wang2, Kimberly Webster1,3, Brian Caffo2, Kyrana Tsapkini1;1Department of Neurology, Johns Hopkins Medicine, Baltimore, MD, 2Department of Biostatistics, Johns Hopkins School of Public Health, Baltimore, MD, 3Department of Otolaryngology, Johns Hopkins Medicine, Baltimore, MD

Introduction: The effects of transcranial direct current stimulation (tDCS) on brain functional connectivity have been explored in healthy aging (Stagg 2014) as well as stroke (Marangolo 2016). However, findings are still unclear. Furthermore, there is relatively little known about the effects of tDCS on functional connectivity in neurodegenerative disease. In the present study, we aimed to assess the effects of anodal tDCS over the left inferior frontal gyrus (IFG) on resting-state functional connectivity in a group of patients with primary progressive aphasia. Methods: We used a within-subjects crossover design, with two phases of 15 consecutive days of either tDCS or sham therapy with a 2-month wash-out period. Anodal, left-IFG tDCS (2x2 inches, 2 mA/minute) was administered for 20 minutes each day, simultaneous with the start of daily, hour-long oral and written naming therapy. For 25 participants, rsfMRI data were acquired for 7 minutes (210 time-point acquisitions) before, after, and 2 months after phase one of intervention. For this analysis we used MRICloud (Oishi 2009), an automated image parcellation approach (atlas-based analysis (ABA)), in which the brain was divided into 283 structures. In an ROI-ROI analysis, Pearson’s correlation coefficients were obtained from averaged time courses of each region and z-transformed with Fisher’s method. Regions selected for analysis were the left IFG opercularis, orbitalis, and triangularis (stimulated area) and other common written and oral language production areas in the left hemisphere (MFG, SPG, SMG, AG, STG, MTG, ITG and FuG), as well as their right homologues. For each pair of ROIs, we measured change in correlation immediately after and 2 months post intervention as compared to before intervention. Results: Behaviorally, gains in written naming scores (both trained and untrained items) in the tDCS condition were significantly greater than those in sham (p<0.05). Imaging analysis revealed three main results. 1) Anodal stimulation over the left IFG significantly increased functional connectivity within the IFG between its subregions. 2) Within the language network, connectivity between the left IFG and other areas of the language network (MTG and fusiform gyrus) decreased in tDCS relative to sham (after correcting for multiple comparisons). 3) Composite scores for neither the language network nor the default mode network showed any significant difference between tDCS and sham. Discussion: Our results align with previous results in healthy aging but not in stroke populations and show that tDCS downregulates the hyperactivity usually observed in frontal areas (Amadi 2013) and upregulates hypoactivity in posterior areas in an adaptive way, as it corresponds to behavioral improvements. These preliminary results show that downregulation of hyperactivity in frontal areas may be one mechanism for effective tDCS. Acknowledgements: Thank you to the Science of Learning Institute at Johns Hopkins University and the National Institute of Health (NIDCD) for award R01 DC014475. References: Stagg CJ, Bachtiar V, Amadi U, et al. Elife. 2014;3:e01465. Marangolo P, Fiori V, Sabatini U, et al. J Cogn Neurosci. 2016;28:724–738. Oishi K, Faria A, Jiang H, et al. NeuroImage. 2009;46(2):486-499. Amadi U, Ilie A, Johansen-Berg H, Stagg CJ. NeuroImage. 2013;88C:155-161.

Topic Area: Language Therapy

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