Dual-hemisphere transcranial direct current stimulation over primary motor cortex enhances consolidation of a ballistic thumb movement

Abstract

Transcranial direct current stimulation (tDCS) is a noninvasive technique that modulates motor performance and learning. Previous studies have shown that tDCS over the primary motor cortex (M1) can facilitate consolidation of various motor skills. However, the effect of tDCS on consolidation of newly learned ballistic movements remains unknown. The present study tested the hypothesis that tDCS over M1 enhances consolidation of ballistic thumb movements in healthy adults. Twenty-eight healthy subjects participated in an experiment with a single-blind, sham-controlled, between-group design. Fourteen subjects practiced a ballistic movement with their left thumb during dual-hemisphere tDCS. Subjects received 1mA anodal tDCS over the contralateral M1 and 1mA cathodal tDCS over the ipsilateral M1 for 25min during the training session. The remaining 14 subjects underwent identical training sessions, except that dual-hemisphere tDCS was applied for only the first 15s (sham group). All subjects performed the task again at 1h and 24h later. Primary measurements examined improvement in peak acceleration of the ballistic thumb movement at 1h and 24h after stimulation. Improved peak acceleration was significantly greater in the tDCS group (144.2±15.1%) than in the sham group (98.7±9.1%) (P<0.05) at 24h, but not 1h, after stimulation. Thus, dual-hemisphere tDCS over M1 enhanced consolidation of ballistic thumb movement in healthy adults. Dual-hemisphere tDCS over M1 may be useful to improve elemental motor behaviors, such as ballistic movements, in patients with subcortical strokes.

Optimizing Transcranial Direct Current Stimulation Protocols to Promote Long-Term Learning

“…For example, there have been rapid consolidation effects where group differences only begin to emerge in the minutes or hours after stimulation, or become stronger/more robust with time (e.g., Clark et al 2012;Ehsani et al 2016;Hoy et al 2014;Javadi and Cheng 2013;Penolazzi et al 2013;Reis et al 2015). Similarly, overnight consolidation has been enhanced when performance is measured the next day, despite a lack of group differences on day 1 (Koyama et al 2015;Martin et al 2014), and even cognitive training studies that failed to show immediate tDCS-related enhancements have still demonstrated greater tDCS-related retention a couple months later (Jones et al 2015;Martin et al 2013;Stephens and Berryhill 2016).…”

Modulating Motor Learning through Transcranial Direct-Current Stimulation: An Integrative View

“…Galea and Celnik (2009) showed a significant effect on training by applying tDCS during the training, an effect that is similarly found with sequence-learning (Stagg et al, 2011). Furthermore, recent results showed enhanced retention of ballistic thumb movements when M1-atDCS was applied during training when evaluating both peak velocities and accelerations of thumb movements (Koyama et al, 2015; Rroji et al, 2015). …”

Polarity-independent effects of transcranial direct current stimulation over the bilateral opercular somatosensory region

“…We applied a bihemispheric tDCS protocol, which is a powerful strategy for controlling brain excitability and various neurological functions. Because of its greater impact on interhemispheric projections, bihemispheric tDCS applied simultaneously is more effective than unihemispheric tDCS for modulating motor performance and sensory perception 15 , 16 . Thus, bihemispheric tDCS potentiates the effects of anodal stimulation to one hemisphere through additional modulation of interhemispheric interactions by cathodal stimulation to the contralateral hemisphere.…”