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Poster E44, Saturday, August 18, 3:00 – 4:45 pm, Room 2000AB

Continuous theta burst stimulation over right pars triangularis facilitates naming abilities in chronic post-stroke aphasia by enhancing phonological access

Denise Y. Harvey1,2, Joely A Mass1, Priyanka P Shah-Basak1, Rachel Wurzman1, Olufunsho Faseyitan1, Daniela L Sacchetti1, Laura DeLoretta1, Roy H Hamilton1;1Department of Neurology, University of Pennsylvania, 2Research Department, Moss Rehabilitation Research Institute

Repetitive transcranial magnetic stimulation (rTMS) has been used experimentally to facilitate naming abilities in individuals with chronic post-stroke aphasia. However, due to the relative infancy of rTMS as a treatment for aphasia, the field has yet to establish criteria for determining who is a good candidate for this treatment approach. To better understand who is most likely to benefit from rTMS therapy, we explored whether variability in rTMS response is related to the severity and/or type (i.e., locus) of naming impairment. Eleven participants with chronic post-stroke aphasia received continuous theta burst stimulation (cTBS) – an inhibitory form of rTMS – to the right hemisphere homologue of Broca’s area (i.e., right pars triangularis [rPTr]) and a control site (i.e., vertex) administered in separate sessions. Prior to stimulation, we obtained two baseline measurements of picture naming ability to determine the extent and type of naming impairment. Items presented for naming during stimulation were those that were named incorrectly in one or both of the baseline sessions (i.e., inconsistent versus wrong items, respectively). Baseline naming impairment severity was operationalized as the percentage of erroneous responses averaged across the two baselines. To identify the primary locus of naming impairment, we conducted in-depth analyses of participants’ error profiles (i.e., semantic versus phonological errors). The findings revealed that, relative to vertex stimulation, cTBS of the rPTr improved naming of inconsistent, but not wrong, items for individuals with more severe baseline naming impairment, as assessed via a median split of baseline naming performance (p = .04). Interestingly, however, naming impairment severity was not significantly correlated with cTBS-induced naming improvements across all participants (p = .80). Instead, we found that the extent of phonological access impairment was marginally correlated with overall naming improvements following rPTr stimulation (p = .057), but not vertex (p = .85). Critically, naming improvements among these individuals specifically manifested in fewer errors arising at this stage of the production system, i.e. significant decrease in phonological (p = .04), but not semantic (p = .56), errors following cTBS of the rPTr. Neither the degree of phonological nor semantic access impairment predicted changes in naming performance following cTBS of the vertex (p’s > .12). To our knowledge, this is the first study to examine the characteristics of naming impairment in aphasia as it relates to variable TMS treatment outcomes. The findings from this research not only lay the groundwork for incorporating cognitive models of word retrieval failure in future studies of TMS in aphasia, but they also have the potential to inform the stratification of patients into effective TMS protocols. In the current study, we provide evidence that individuals with word retrieval deficits localized to phonological access may be optimal candidates for TMS treatment protocols involving inhibitory stimulation of the rPTr.

Topic Area: Language Disorders