Functional characteristics in supraspinal networks and sensorimotor function following individualized dose-controlled HD-tDCS during foot core exercise in chronic ankle instability

BACKGROUND: This study aimed to investigate the effects of individualized dose-controlled high-definition transcranial direct current stimulation (HD-tDCS) in combination with foot core exercise (FCE) on functional supraspinal network characteristics and sensorimotor function in individuals with chronic ankle instability (CAI). METHODS: In this double-blind, randomized controlled trial, 34 participants were allocated into 2 groups: individualized dose-controlled HD-tDCS combined with FCE and sham stimulation combined with FCE (control group). Participants received 20 min of stimulation concurrent with FCE, 3 times per week over a 4-week period. Assessments included task-related functional magnetic resonance imaging and ankle force sense, conducted at baseline and post-intervention. RESULTS: Compared with baseline and the control group, the individualized dose-controlled HD-tDCS combined with FCE reduced task-related cortical activation in the bilateral inferior parietal lobule and the right supplementary motor area (rSMA) and increased functional connectivity (FC) between the left inferior parietal lobule and the right putamen. Additionally, improved dorsiflexion, inversion, and eversion force senses were observed. Besides, changes in force sense were negatively correlated with changes in signal intensities in the right inferior parietal lobule and rSMA, and marginally significantly associated with changes in FC between the left inferior parietal lobule and right putamen. CONCLUSION: A 4-week intervention of individualized dose-controlled HD-tDCS combined with FCE effectively reduced cortical activation during ankle motor tasks, strengthened FC within relevant supraspinal networks, and enhanced sensorimotor function in individuals with CAI.