Insights on an Emerging Scientific Field: The Role of fNIRS in Balance and Gait Research

Since my first ISPGR World Conference in Fort Lauderdale in 2017, I have seen many studies on functional near-infrared spectroscopy (fNIRS). Whilst its use is still controversial, research has demonstrated that fNIRS assessments are feasible, and their results not only reinforce previous theories related to motor control but also bring new hypotheses regarding the involvement of cortical areas in balance and gait tasks, shedding light on a better understanding of fall risk. It was a great pleasure to have received the ISPGR Emerging Scientist Award 2023 because of my work in this emerging scientific field. Below, I summarise my research findings using fNIRS to examine complex balance and gait.

In a series of studies, I examined older adults at low and high fall risk and people with Parkinson’s disease (PD). These participants performed a range of stepping tests (simple choice stepping reaction time test (CSRT), CSRT with inhibitory response (iCSRT) and a Stroop version of CSRT (SST)), along with an adaptive walking test. The cortical areas examined were the prefrontal cortex (PFC), supplementary motor area (SMA) and premotor cortex (PMC). Older adults at high fall risk exhibited increased PFC activity and stepping response variability when completing the SST test compared to older adults at low fall risk and compared to the CSRT test [1]. In PD, the pattern of cortical activity differed. Whilst older adults increased their cortical activity (PFC, SMA and PMC) to handle more complex stepping tests (iCSRT and SST), people with PD exhibited a “slowdown” phenomenon, demonstrating reduced cortical activity in the same areas [2]. Finally, during adaptive gait, people with PD had little or no additional PFC, SMA, and PMC capacity beyond what they needed for simple walking and, therefore, presented with a more conservative gait pattern than their healthy peers [3].

Altogether, these results elucidate that older adults may not cope with task demands, relying heavily on their cortical resources, which reflects their increased risk of falling. Moreover, this increased cortical activity seems to reflect a compensatory process for deficits in postural control or a degree of neural inefficiency in those at high fall risk. In PD, the reduced cortical activity during complex stepping tests might reflect multiple pathways and/or subcortical damage, resulting in deficient use of cognitive and motor resources and poor overall motor behavior.  Finally, the cortical activity and behavior exhibited by people with PD during adaptive gait appear consistent with concepts of compensatory over-activation and capacity limitation.

Publications

[1]  Paulo H S Pelicioni, Stephen R Lord, Daina L Sturnieks, Bethany Halmy, Jasmine C Menant. Cognitive and Motor Cortical Activity During Cognitively Demanding Stepping Tasks in Older People at Low and High Risk of Falling. Front Med (Lausanne). 2021; 8: 554231. doi: 10.3389/fmed.2021.554231

[2]  Paulo H S Pelicioni, Stephen R Lord, Yoshiro Okubo, Daina L Sturnieks, Jasmine C Menant. People With Parkinson’s Disease Exhibit Reduced Cognitive and Motor Cortical Activity When Undertaking Complex Stepping Tasks Requiring Inhibitory Control. Neurorehabil Neural Repair. 2020 Dec;34(12):1088-1098. doi: 10.1177/1545968320969943.

[3]  Paulo H S Pelicioni, Stephen R Lord, Yoshiro Okubo, Jasmine C Menant. Cortical activation during gait adaptability in people with Parkinson’s disease. Gait Posture. 2022 Jan:91:247-253. doi: 10.1016/j.gaitpost.2021.10.038.

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