Modulation of cerebral activation strategies by training mode in stratified stroke cohorts: an fNIRS study

Robot-assisted training (RAT) exhibits inconsistent efficacy in post-stroke upper limb rehabilitation, with its underlying neural mechanisms remaining unclear. This study aimed to investigate how different therapy modes modulate cerebral activation strategies in distinct subgroups of stroke patients.

We utilized functional near-infrared spectroscopy (fNIRS) to investigate differences in cortical activation strategies, specifically the response sensitivity to various robotic training modes, by stratifying forty-one patients based on functional level, disease chronicity, and hemiplegic side. In a single session, each participant underwent four RAT modes (Passive, Assistive-active, Active, and Mirror) while a 48-channel fNIRS system monitored cortical activation.

Our results revealed no statistically significant differences in global mean activation intensity between any of the subgroups (p > 0.05). Instead, the core finding was a clear dichotomy in neural strategy: low-function, subacute, and left-hemiplegia groups were highly "mode-sensitive," exhibiting significant changes in brain activation across different training modes (e.g., Active vs. Mirror, p < 0.05). Conversely, high-function, chronic, and right-hemiplegia groups were "mode-consolidated," demonstrating a stable activation pattern with almost no significant differences among the active modes.

We conclude that the core neural mechanism of post-stroke recovery is characterized not by simple changes in activation intensity, but by a strategic evolution from a flexible, cue-dependent "mode-sensitive" state to a more automated "mode-consolidated" state. This distinction provides a robust neurophysiological rationale for personalizing rehabilitation, enabling clinicians to strategically match therapeutic stimuli to a patient's specific neural profile-applying diversified training to "mode-sensitive" patients and high-load challenges to "mode-consolidated" patients-to break through rehabilitation plateaus.