Within-Session Reliability of fNIRS in Robot-Assisted Upper-Limb Training

Area of Science:

• Neuroscience
• Rehabilitation Engineering
• Biomedical Instrumentation

Background:

• Functional near-infrared spectroscopy (fNIRS) is a promising noninvasive neuroimaging technique for neurofeedback in robot-assisted rehabilitation.
• Previous studies confirmed fNIRS reliability for non-motor and fine-motor tasks across sessions.
• Reliability of fNIRS for gross-motor tasks within a training session and across different parameters remained unexplored.

Purpose of the Study:

• To investigate the within-session reliability of fNIRS responses during robot-assisted gross-motor tasks.
• To evaluate fNIRS reliability across different robot-assisted training parameters (Passive, Active1, Active2).
• To assess both spatial and temporal reliability of fNIRS signals during motor rehabilitation.

Main Methods:

• Ten healthy participants performed right elbow extension-flexion using a robot-assisted system in three modes: Passive, Active1, and Active2.
• fNIRS data were collected across three identical runs to assess within-session reliability.
• Reliability was quantified using map-wise (R²) and cluster-wise (R_overlap) spatial reproducibility and intraclass correlation (ICC) for temporal features (Slope, Max/Min, Mean).

Main Results:

• Good spatial reliability was observed at the subject level (R² up to 0.69, R_overlap up to 0.68).
• Within-session temporal reliabilities for Slope, Max/Min, and Mean ranged from good to excellent (ICC < 0.86).
• Positive correlation between within-session reliability and training intensity was found, with an exception for HbO temporal reliability in Active2 mode.

Conclusions:

• fNIRS demonstrates good within-session reliability for gross-motor tasks in robot-assisted rehabilitation.
• The findings support the use of fNIRS as a reliable neurofeedback tool for closed-loop rehabilitation systems.
• Training parameters influence fNIRS reliability, suggesting potential for personalized neurofeedback protocols.