Poster A60, Tuesday, August 20, 2019, 10:15 am – 12:00 pm, Restaurant Hall
Enhancing Speech Motor Learning Recovery With Noninvasive Brain Stimulation: Behavioral and neurobiological evidence
Adam Buchwald1, Nicolette Khosa1, Stacey Rimikis1, E. Susan Duncan2;1New York University, 2Louisiana State University
Introduction. The potential to enhance stroke recovery using transcranial direct current stimulation (tDCS) has been the topic of active research and controversy. While tDCS has been studied as a tool to facilitate word production in aphasia (Fridriksson et al., 2018), it has not been previously tested as a tool to facilitate recovery involving acquired speech impairment. We report a single-subject intervention design successfully using tDCS applied to perilesional pre-central gyrus as an adjunct to a speech motor learning treatment, with enhanced behavioral outcomes supported by changes in resting state functional connectivity. Methods. P1 (64, M, RH) suffered extensive LH MCA CVA >10 years ago, affecting fronto-parietal regions. He presented with moderate-severe AOS, with slowed, dysfluent speech containing frequent distortions. Treatment design. We employed a multiple-baseline/multiple-probe crossover design with two 9-session treatment phases treating different targets. Motor learning-based treatment sessions (~40mins) included pre-practice (~5mins) followed by practice (feedback on 25% of items). Probes were obtained weekly during treatment, and baseline and maintenance sessions tested all items from both phases (N=192). Three sessions at each point evaluated short-term (2wks post each phase) and long-term (6 months post-treatment) maintenance. tDCS protocol. Electrode placement was determined using individualized current modeling based on structural MRI (anode: T3, cathode: F4 which maximized current flow to residual premotor and motor cortices). P1 received active tDCS in Phase 1, and sham tDCS during Phase 2. Current (1mA) was administered at the beginning of each treatment session (active: 20 minutes; sham: 30 seconds). Neuroimaging. MRI data were acquired on three occasions (3T Siemens Prisma). Session 1 (pre-tx) included the structural T1 used for targeting (1mm3 voxels). Sessions 2 and 3 were performed two days after the end of each treatment phase. Each session included twelve minutes of resting-state fMRI acquisition (TR=1650, TE=35ms, FA=72º, FoV=216x216mm, 50 axial slices [2mm], in-plane voxel size=2.4x2.4mm). To evaluate connectivity changes, we selected six homologous regions associated with speech production using the Fan et al. (2016) parcellation. Regions corresponded to pars opercularis (x2), ventral pre-central gyrus (x2), ventral post-central gyrus and anterior insula. Functional connectivity was calculated using interregional time series correlations: (i) within the left hemisphere, (ii) within the right hemisphere, and (iii) inter-hemispherically. Results Behavioral data were scored for accuracy by two blinded independent coders. For both phases, all maintenance sessions (short-term and long-term) were more accurate than baseline (no overlapping data). Effect sizes (Cohen’s d) were computed at maintenance and follow-up. Both treatment phases exhibited small effect sizes at maintenance (active: 2.06; sham: 2.90), with a larger long-term retention effect size for active (4.67) vs. sham (2.20), suggesting enhanced retention of speech motor learning during active stimulation. Between Session 1 (baseline) and Session 2 (following active tDCS), resting-state connectivity increased within both the left hemisphere (p<0.0001, t=5.34, 95% CI:[0.101,0.237]) and inter-hemispherically (p<0.0001, t=6.86, 95% CI:[0.105,0.194]). No other comparisons between time points yielded significant changes. Discussion While further exploration/replication is needed, we interpret these behavioral and neurological findings as preliminary support for adjuvant effects of tDCS paired with traditional speech motor learning intervention.
Themes: Disorders: Acquired, Speech Motor Control
Method: Neurostimulation