A Systematic Review on Functional Near-Infrared Spectroscopy Concurrent With Quantitative Balance Assessment.

Functional near-infrared spectroscopy (fNIRS) can be used to study activity patterns in different brain cortical areas involved in balance control. This systematic review aims to report on studies in which balance performance has been quantitatively assessed concurrent with fNIRS neuroimaging. Following the PRISMA guidelines, relevant keywords were used for the search through the Scopus and Web of Science databases. Sixty-eight studies met the inclusion criteria and were imported for data extraction. Information on balance assessment protocols, alterations to the balance control loop, brain regions of interest, fNIRS parameters, the relationships found between brain activity and balance performance, and participant cohort types was extracted. The common balance tasks in fNIRS studies were standing and walking. Standing balance control was mainly measured through sway parameters using force platforms. Walking performance was evaluated through gait parameters mostly assessed by floor sensors or inertial sensors. Some of the balance tasks were challenged through sensory manipulation or dual task interference. Brain activity monitoring via fNIRS was mainly utilized to measure oxygenated haemoglobin concentration in frontal cortex. Out of the 68 included articles, 22 studies investigated and found the relationships between activity patterns in different cortical areas and balance measures. In 32 studies, the effects of different factors such as long-term, biological, and psychological conditions on brain activity and balance performance were studied. This study provides a systematic review on fNIRS studies in which quantitative balance assessment is employed to provide a better understanding of neuromotor control of balance.