fNIRS response during walking - Artefact or cortical activity? A systematic review

Area of Science:

• Neuroscience
• Biomedical Engineering
• Rehabilitation Science

Background:

• Functional near-infrared spectroscopy (fNIRS) is increasingly used to study brain activity during walking.
• Existing fNIRS walking studies exhibit significant variability in design and data analysis.
• This variability complicates the interpretation and comparison of findings across different research groups.

Purpose of the Study:

• To systematically review fNIRS walking study designs in young adults, older adults, and individuals with Parkinson's disease (PD).
• To examine signal processing techniques for reducing artifacts and physiological noise in fNIRS data.
• To provide evidence-based recommendations for optimizing fNIRS walking study methodologies and analysis.

Main Methods:

• A systematic electronic literature search was conducted using keywords related to the measurement technique, cohort, and walking task.
• Thirty-one studies meeting specific inclusion criteria were analyzed.
• Protocols for study design, artifact removal, and noise reduction were evaluated.

Main Results:

• Significant heterogeneity was observed in fNIRS walking study protocols and signal processing methods.
• Inconsistencies in fNIRS signals were noted across different conditions, including rest vs. walking, walking speed, and task complexity.
• Variations in methodologies contribute to inconsistencies in study findings.

Conclusions:

• Conducting fNIRS studies during walking presents substantial technical and methodological challenges.
• Recommendations are provided for developing robust methodologies and appropriate signal processing techniques.
• A theoretical framework considering the physiology of hemodynamic responses is suggested for future fNIRS walking research.