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Poster E15, Friday, November 10, 10:00 – 11:15 am, Harborview and Loch Raven Ballrooms

Effect of rTMS on Brain Activation and Naming Performance in Chronic Aphasia: Results from a Pilot Participant

Michelle Gravier1, Steven Forman1,2, Michael Dickey1,2, William Hula1,2, Patrick Doyle1,2;1VA Pittsburgh Healthcare System, 2University of Pittsburgh

INTRODUCTION Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive brain stimulation technique that can focally modulate activity in targeted brain regions. Multiple sessions of 1Hz inhibitory rTMS targeting right hemisphere Pars Triangularis (RH PTr) in people with chronic aphasia can result in improved naming abilities (e.g. Naeser et al., 2005). These improvements accrue over time, and may persist even after rTMS has ended (Barwood et al., 2012). It has been proposed that rTMS induces this improvement by reducing compensatory activity in the RH PTr, allowing for recruitment of more efficient left hemisphere (LH) brain areas (Heiss & Thiel, 2006; Hamilton et al., 2011). However, existing neuroimaging evidence has not definitively established this hypothesized link between reduced RH PTr activation and improved naming. The goal of this study was therefore to investigate the neurological mechanisms underlying the effect of rTMS on naming performance in one individual with chronic aphasia. METHOD The participant was a 44 year-old male, 14 years post stroke onset with moderate to severe non-fluent aphasia and marked word-finding difficulties. MRI: The participant underwent functional magnetic resonance (fMRI) scans at three time points: prior to receiving rTMS (“baseline”), immediately following the first rTMS session (“post-rTMS”), and following conclusion of the rTMS series (“post-treatment”). Scans were acquired using a 3.0 Tesla Siemens scanner. The participant was asked to name black-and-white picture stimuli (Snodgrass and Vanderwort, 1980) as quickly and accurately as possible while in the scanner. An individualized map of brain activity was generated for the contrast of naming > baseline (crosshair fixation) for each scan. Activation maps for all contrasts were thresholded voxel-wise at p=0.05 (cluster-corrected using Family-Wise Error). All processing was performed using SPM12. rTMS: The subject received 1200 pulses (20 minutes) of 1Hz rTMS at 90% of motor threshold to RH PTr in 10 daily sessions, over two weeks. Naming: The participant’s naming performance was assessed with the Philadelphia Naming Test (Roach et al., 1996) prior to the TMS sessions and again one week after the final TMS session RESULTS From pre-rTMS to post- rTMS, the participant demonstrated significant naming improvements (p<0.05) on the Philadelphia Naming Test (PNT). This improvement was accompanied by a decrease in naming-related (picture>crosshair) activation in the targeted brain region (RH PTr) from baseline to post-rTMS (immediately following the first rTMS session). This change in RH PTr activation was maintained at the post-treatment time point. However, functional activation did not shift towards perilesional LH, but instead increased in RH temporal regions. DISCUSSION The finding that the rTMS-induced naming improvement was associated with a decrease in RH PTr activation is consistent with the hypothesized mechanism behind TMS effects in chronic aphasia (Heiss & Thiel, 2006). However, the observed inter-hemispheric RH activation shift stands in contrast to previous findings (Martin & Naeser, 2009). The significant size of this participant’s LH lesion (extending to much/all of the LH) may have precluded LH recruitment. These preliminary results thus leave open the question of whether rTMS would have been more beneficial for participants with more intact LH cortex.

Topic Area: Language Disorders

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