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Abstract

The improvement of acute stroke treatment has increased survival, leaving more people in rehabilitative care. The recovery of function, however, typically stagnates after initial progress. Transcranial direct current stimulation (tDCS) has been suggested to facilitate recovery beyond this plateau. However, inconsistent results of tDCS effects were found in chronic patients, probably due to varying behavioural assessments with low spatial or temporal resolution, a selection bias introduced through group designs and small sample sizes. Here, we used high-resolution kinematic assessments to inspect a wide range of sensorimotor functions using established protocols for unilateral (utDCS) and bilateral tDCS (btDCS) in a cross-over, double-blind and sham-controlled clinical trial. 24 patients underwent all tDCS conditions (sessions separated by one week) concurrent to kinematic assessments. tDCS-induced effects were measured on 4 tasks. Kinematic parameters were extracted across these tasks and corrected for age and Fugl-Meyer score. The estimates were then compared between sham vs. utDCS and sham vs. btDCS, respectively, using paired-samples t-tests and classified as (1) non-significant changes, (2) significant increases or (3) decreases in performance. Class distributions across parameters were then compared between real and permuted data to account for falsely positive significance tests. utDCS induced significant increases in 7 and decreases in 18 parameters, btDCS increases in 11 and decreases in 15 parameters. The class distributions differed significantly between real and permuted data, indicating a profound tDCS effect. Our approach provides a new avenue for investigating tDCS effects across different sensorimotor domains after stroke. The results demonstrate the efficacy of tDCS to modulate sensorimotor function after stroke, but also indicate that the induced effects are complex and bidirectional.