Discussion
chronic stroke, stroke
STROKE
We demonstrated that, for the first time, concurrent bihemispheric tDCS during task-oriented training conferred benefits on motor recovery of the paretic UE, compared to sham stimulation in early subacute stroke patients. These individual UE improvements were associated with bilateral intrahemispheric FC changes in the targeted motor network. However, there was high variability of individual FC changes and no significant difference between groups. The results suggest that the neural circuits involved in tDCS-related subacute recovery are likely reorganized in the bilateral cortices. Importantly, our RCT of bihemispheric tDCS stratified patients according to the residual CST integrity, a prognostic biomarker for motor recovery [Our findings of bihemispheric tDCS for UE motor recovery are in line with previous studies in chronic stroke patients [The effect of bihemispheric tDCS on ARAT was not as prominent as FMA-UE, although there was greater improvement of ARAT immediately after real tDCS compared with sham tDCS. One explanation could be that ARAT has stronger floor effect and ceiling effect than FMA-UE in acute and subacute stroke patients [The mechanisms of bihemispheric tDCS for motor recovery in subacute stroke patients remain unclear. In our analysis of functional networks underlying motor recovery, bihemispheric tDCS-induced individual UE improvements were associated with intrahemispheric FCThere are limitations of this study. First, because of the enrollment criteria for relatively homogenous stroke patients, the small sample size weakened external validity and further resting-state FC changes and subgroup analysis of tDCS responsiveness by patient-specific factors [