Offline effects of transcranial direct current stimulation on reaction times of lower extremity movements in people after stroke: a pilot cross-over study

Abstract

BackgroundTranscranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that has shown promise for rehabilitation after stroke. Ipsilesional anodal tDCS (a-tDCS) over the motor cortex increases corticospinal excitability, while contralesional cathodal tDCS (c-tDCS) restores interhemispheric balance, both resulting in offline improved reaction times of delayed voluntary upper-extremity movements. We aimed to investigate whether tDCS would also have a beneficial effect on delayed leg motor responses after stroke. In addition, we identified whether variability in tDCS effects was associated with the level of leg motor function.MethodsIn a cross-over design, 13 people with chronic stroke completed three 15-min sessions of anodal, cathodal and sham stimulation over the primary motor cortex on separate days in an order balanced across participants. Directly after stimulation, participants performed a comprehensive set of lower-extremity tasks involving the paretic tibialis anterior (TA): voluntary ankle-dorsiflexion, gait initiation, and backward balance perturbation. For all tasks, TA onset latencies were determined. In addition, leg motor function was determined by the Fugl-Meyer Assessment – leg score (FMA-L). Repeated measures ANOVA was used to reveal tDCS effects on reaction times. Pearson correlation coefficients were used to establish the relation between tDCS effects and leg motor function.ResultsFor all tasks, TA reaction times did not differ across tDCS sessions. For gait initiation and backward balance perturbation, differences between sham and active stimulation (a-tDCS or c-tDCS) did not correlate with leg motor function. Yet, for ankle dorsiflexion, individual reaction time differences between c-tDCS and sham were strongly associated with FMA-L, with more severely impaired patients exhibiting slower paretic reaction times following c-tDCS.ConclusionWe found no evidence for offline tDCS-induced benefits. Interestingly, we found that c-tDCS may have unfavorable effects on voluntary control of the paretic leg in severely impaired patients with chronic stroke. This finding points at potential vicarious control from the unaffected hemisphere to the paretic leg. The absence of tDCS-induced effects on gait and balance, two functionally relevant tasks, shows that such motor behavior is inadequately stimulated by currently used tDCS applications.Trial registrationThe study is registered in the Netherlands Trial Register (NL5684; April 13th, 2016).

Computer-delivered Cognitive Training and Transcranial Direct Current Stimulation in Patients with HIV-associated Neurocognitive Disorder: A Randomized Trial

“…Others have reported that tDCS may have a facilitating effect on reaction time with anodal stimulation over primary motor cortex, but Molero-Chamizo et al found that the effect was time dependent (Molero-Chamizo et al, 2018). Others have also failed to find an effect of tDCS (Coppens, Staring, Nonnekes, Geurts, & Weerdesteyn, 2019;Seidel & Ragert, 2019) We found more substantial improvements in measures of psychomotor speed, including a significant interaction of group by time for the WAIS-IV Coding subtest.…”

“…Others have reported that tDCS may have a facilitating effect on reaction time with anodal stimulation over primary motor cortex, but Molero-Chamizo et al found that the effect was time dependent (Molero-Chamizo et al, 2018). Others have also failed to find an effect of tDCS (Coppens, Staring, Nonnekes, Geurts, & Weerdesteyn, 2019;Seidel & Ragert, 2019) on reaction time. Our hypothesis of an effect on reaction time was based primarily on the nature of the training task (a fast-paced computer game), but neither statistical tests nor inspection of mean plots by groups (not presented) suggested an effect for either of the active treatment groups.…”

Effect of non-invasive brain stimulation on lower limb function in patients after stroke: A PRISMA-compliant systematic review and meta-analysis

“…Supplementary Tables 1 and 2 showed study characteristics of included studies. Finally, the present study included 16 and 12 articles for tDCS 5,7,[10][11][12][13][14][15][16][17][18][19][20][21][22][23] and rTMS 6,8,[24][25][26][27][28][29][30][31][32][33] , respectively. Studies for tDCS included 10 RCTs (including 110 patients after stroke given tDCS and 110 patients given sham tDCS over motor cortex) and 6 crossover trails (including 102 patients after stroke).…”

Computer-Delivered Cognitive Training and Transcranial Direct Current Stimulation in Patients With HIV-Associated Neurocognitive Disorder: A Randomized Trial

“…Others have reported that tDCS may have a facilitating effect on reaction time with anodal stimulation over primary motor cortex, but Molero-Chamizo et al (2018) found that the effect was time dependent. Others have also failed to find an effect of tDCS ( Coppens et al, 2019 ; Seidel and Ragert, 2019 ) on reaction time. Our hypothesis of an effect on reaction time was based primarily on the nature of the training task (a fast-paced computer game), but neither statistical tests nor inspection of mean plots by groups (not presented) suggested an effect for either of the active treatment groups.…”