Single-Case Design for Network-based BCI Rehabilitation: Individual Learning Trajectories and Effects of Motor Imagery Timing in Stroke Patients
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Background
Motor imagery (MI) brain-computer interfaces (BCIs) are increasingly investigated for promoting motor recovery after stroke. However, it remains unclear how BCI control improves through repeated training in stroke patients and whether the timing of MI decoding systematically influences this trajectory.
Methods
To address this question, we implemented a single-case experimental design involving five chronic stroke patients enrolling in a longitudinal electroencephalography MI-BCI training involving their affected hand. Across 18 sessions conducted over six weeks, the onset of a fixed-duration MI decoding window was randomized to occur 1, 2, or 3 s after cue onset according to an alternating-treatments single-case design. Notably, the BCI combined spectral power and functional connectivity features to classify MI states.
Results
The MI classification timing had no significant effect on BCI accuracy, fatigue, or spasticity. BCI accuracy increased across training in four of five patients and was accompanied by patient-specific longitudinal changes in local spectral activity and functional connectivity. These convergent trajectories were consistent with acquisition of BCI control, but were not accompanied by clinically meaningful improvement in motor function.
Conclusions
Varying the onset of the MI decoding window provided no systematic benefit for BCI control. Instead, differences in neurophysiological trajectories across patients indicate that MI decoding parameters need to be personalized and reassessed throughout the training. Overall, these findings inform more individualized and effective BCI settings for neuromotor stroke rehabilitation.
Trial registration
ClinicalTrials.gov, NCT06951035 , registered 30 April 2025
