Objective: To assess single-session effects of three different types of stimuli known to increase cortical excitability when combined with functional task practice. Design: Randomized cross-over trial. Participants: A total of 24 participants with chronic cervical spinal cord injury. Interventions: One 30-minute session of each, applied concurrently with functional task practice: transcranial direct current stimulation, vibration, and transcutaneous electrical nerve stimulation. Measurements: Nine-hole Peg Test, pinch force, visuomotor tracking, and cortical excitability were collected at pretest, posttest and late posttest (30 minutes after). Early effects (posttest minus pretest) and short-term persistence (late posttest minus pretest) were assessed using a general linear mixed model. Magnitude of effect size was assessed using the Cohen’s d. Results: Transcutaneous electrical nerve stimulation was associated with moderate, significant early effects and short-term persistence on Nine-hole Peg Test performance (1.8 ±1.8, p = 0.003, d = 0.59; 2.0 ±2.5, p < 0.001, Cohen’s d = 0.65, respectively). Transcranial direct current stimulation (1.8 ±2.5, p = 0.003, Cohen’s d = 0.52) was also associated with significant short-term persistence of moderate size on Nine-hole Peg Test performance (1.8 ±2.5, p = 0.003, Cohen’s d = 0.52) and visuomotor tracking performance ( p = 0.05, d = 0.51). Early effects on corticomotor excitability were significant for transcutaneous electrical nerve stimulation ( p = 0.003), approached significance for transcranial direct current stimulation ( p = 0.07), and only vibration was associated with significant short-term persistence ( p = 0.006). Conclusions: Meaningful improvements in aspects of hand-related function that persisted at least 30 minutes after intervention were observed with transcutaneous electrical nerve stimulation and transcranial direct current stimulation, when combined with functional task practice.
Noninvasive techniques for probing neurocircuitry and treating illness: vagus nerve stimulation (VNS), transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS)