Cortical activity during a gait adaptability task in older adults

Introduction: The ability to adapt gait when negotiating unexpected hazards is crucial to maintain stability and avoid falling. In older people, walking under more demanding conditions requires greater cortical engagement, especially in brain regions involved in locomotion, such as the prefrontal cortex and pre-motor regions (Pelicioni et al., 2022). However, it is unclear whether cortical activity in these regions of interest: (1) decreases with repeated exposure to a gait adaptability paradigm; (2) differs according to gait adaptability performance. To answer these questions, this study investigated cortical hemodynamic activity using functional near-infrared spectroscopy (fNIRS), during a treadmill-based gait adaptability task in older adults.Methods: Forty healthy older adults (mean (SD) age: 72.2 (4.1) years; n=22 women) performed three paired blocks of two 90 s trials walking at 1.1 m/s on a treadmill: simple walking; and gait adaptability task (GAT). The GAT included 20 stimuli presented as coloured tiles projected on the treadmill in a random order; participants were required to step on target green tiles and avoid obstacle red tiles. Stepping errors were recorded (i.e., <50 % of the foot stepping on a green tile or <50 % of the foot avoiding a red tile). Oxygenated haemoglobin concentrations [HbO2] in the prefrontal cortex (PFC), supplementary motor area (SMA) and premotor cortex were recorded using fNIRS.Results: Significant time by condition interactions (p<0.05) revealed greater [HbO2] during GAT compared with simple walking for the first block in the PFC (p=0.001) and for the last block in the SMA (p=0.028). Twenty-four participants made at least one mistake in the GAT trials. A significant group by condition in the first block indicated that participants who made errors had significantly greater [HbO2] in the PFC during GAT compared with simple walking (p<0.001).Conclusions: Repeated exposures to a gait adaptability paradigm revealed differential patterns of cortical activation according to the region of interest, possibly owing to their underlying function. The PFC, typically responsible for attention and inhibitory control, apparently became less engaged from the second exposure to the GAT paradigm, with neural activity resembling that of simple walking. In contrast, the SMA, a key region for motor planning, remained engaged at a similar level during GAT across blocks. However, it showed significantly reduced activity between the second and third block during simple walking, possibly indicating increased walking automaticity. Interestingly, participants who made errors engaged the PFC to a greater extent during the GAT compared with controlled walking, suggesting potential neural inefficiency or a capacity limitation in that region of interest.