Differences in brain activation and connectivity during unaffected hand exercise in subacute and convalescent stroke patients

Patients experiencing severe hemiplegia following a stroke struggle to rehabilitate their affected limbs. Cross-education (CE) training emerges as a promising rehabilitation method due to its safety, simplicity, low risk, and ability to effectively improve muscle strength in the affected limb. However, controversy surrounds the neural mechanisms and clinical applications of CE. To address this, we employed functional near-infrared spectroscopy to monitor the response of regions of interest (ROI) and functional connectivity in patients with stroke experiencing severe hemiplegia during one session of 50% maximal voluntary contraction (MVC) strength training with less-affected hand in both subacute and convalescent phases. Our objective was to compare the two stroke groups to gain insight into the potential utility for unilateral training of the less-affected limb as an effective rehabilitation approach during different phases post of stroke.

The findings revealed varying degrees of activation in the ROIs within the affected hemisphere across both groups during the task. Additionally, we found that the subacute stroke patients with severe hemiplegia (SPS) had higher blood oxygen levels in the ipsilesional primary motor (iM1), ipsilesional pre-motor and supplementary motor area (iP-SMA) and contralesional P-SMA (cP-SMA). Functional connectivity strength between the iM1 and contralesional brain regions, as well as between the iP-SMA and ipsilesional ROIs, showed statistically significant differences in SPS compared to convalescent stroke patients with severe hemiplegia (CPS) during a 50% MVC strength training session using the less-affected hand.

Significance statement

Exploring the neural mechanisms underlying one session of 50% MVC strength training with less-affected hand sheds light on a safe therapy. The study enhances our understanding of less-affected hand training and investigates the feasibility as a future rehabilitation approach. Analyzing how one session of 50% MVC strength training with less-affected hand affects brain activation and connectivity could lead to more tailored and effective rehabilitation strategies.