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Poster A53, Wednesday, November 8, 10:30 – 11:45 am, Harborview and Loch Raven Ballrooms

Comparison between the effect of online and offline transcranial direct current stimulation on naming latency in healthy adults

Mohammed F. ALHarbi1,2, Esther S. Kim1;1Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, AB T6G 2G4, Canada, 2College of Medical Rehabilitation Sciences, Taibah University, Madinah, Saudi Arabia

Purpose: Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulation technique that can be used to boost language recovery in post-stroke aphasia and enhance language performance in healthy subjects. Although tDCS intervention studies for anomia have shown promising results, the optimal stimulation parameters are yet to be determined. One of the challenges with administering tDCS as an adjunct treatment for anomia is determining the best time to deliver the stimulation. In motor and cognitive domains, several studies have shown that the effect of tDCS differs when administered concurrently with a behavioral task that is related to the stimulated area (i.e., online stimulation) versus when the stimulation and the behavioral task are administered separately (i.e., offline stimulation). Specifically, some investigators have reported that online stimulation can interfere with motor or cognitive task performance, but this issue of interference has not been fully investigated with respect to naming performance. The purpose of this study is to examine the effect of tDCS on naming performance when tDCS is delivered concurrently(online) compared to sequential (offline) stimulation in healthy adult subjects. Methods: 21 healthy participants were included in the study. A double blinded within-subject crossover experimental design with two conditions (active anodal-tDCS, sham anodal-tDCS) and a 24 hour washout period between the conditions was used. Each participant was asked to name 20 pictures (2 x 10 items) of common objects five times (before, during, immediately post, 10 minutes post, and 20 minutes post-stimulation) in each condition. 1.5 mA A-tDCS was used over Broca’s area with a return electrode over the contralateral supraorbital region for 10 minutes in each session. The participants were randomly allocated to conditions and the presentation of the stimuli was also random. Change in naming latency (in milliseconds) was the dependent variable. Results: Two-way repeated ANOVA with factors condition and time showed no significant differences between the two conditions (sham and active A-tDCS) ( F=1.26, P=0.27) and no significant differences between the offline and online stimulations (F=1.82, P=0.13). Discussion: 10 minutes single tDCS session with 1.5 mA intensity and an active anodal electrode placed over Broca’s area with a return electrode placed over contralateral supraorbital region might not sufficient to induce significant changes in naming latency in healthy subjects. The findings confirm the results of the recent studies where no effects of tDCS stimulation on naming ability have been found following a single session (Horvath et al., 2015; Westwood et al., 2017). Longer stimulation durations might be needed to detect the effect of tDCS and allow for accurate comparison between offline and online tDCS stimulation on naming latency.

Topic Area: Language Disorders

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