Linking brain activation to standing balance performance: A systematic review and meta analysis of functional near-infrared spectroscopy literature

Abstract

Background

Functional Near-Infrared Spectroscopy (fNIRS) holds promise for clinical applications in the field of balance impairment amelioration; however, the relationship between fNIRS metrics and balance performance remains uncertain. We aimed to quantify the correlations between fNIRS-derived brain activation and standing balance performance, and determine variables that influence these associations.

Methods

We systematically reviewed English-language studies, published across PuBMed, PsycINFO, Embase, CINAHL, Ovid Medline, and Web of Science from inception up until July 1, 2024, that assessed standing balance tasks in adults > 18 years old with or without medical diagnosis measured with fNIRS. Pooled correlation coefficients were synthesized using a random effects restricted maximum likelihood model.

Results

Overall, 17 studies were included with 420 participants. Key factors influencing the identified relationships were brain region and participant diagnosis. We identified moderate correlations between balance performance and cortical activation recorded by fNIRS in the supplementary motor area (SMA) (r = 0.52, 95 % CI = 0.39 0.64), and the prefrontal cortex (PFC) (r = 0.47, 95 % CI=0.32 – 0.60). In the PFC, increased oxygenated haemoglobin (HbO) was negatively associated with balance measures. The reverse relationship was reported in the PFC for individuals with physical and cognitive impairment. In the SMA, HbO was positively associated with balance. Few studies found associations between deoxygenated haemoglobin (HbR) and total hemoglobin (HbT) with balance performance.

Significance

Current evidence supports a relationship between fNIRS measures, specifically HbO, with standing balance performance. This relationship depends on the brain region measured, age, and the diagnosis of the participants. To better understand this relationship, there is a need to report standardized balance performance metrics alongside other metrics of interest to better synthesize data across publications. Improved understanding the neural basis of standing balance with fNIRS will lead to more informed interventions for balance rehabilitation.