Cognitive Reserve Moderates the Efficiency of Prefrontal Cortex Activation Patterns of Gait in Older Adults

Abstract

Background: Cognitive reserve (CR) protects against cognitive decline, but whether CR influences the efficiency of cortical control of gait has not been reported. The current study addressed this important gap in the literature. Specifically, we determined the role of CR in moderating the efficiency of functional near-infrared spectroscopy (fNIRS)-derived oxygenated hemoglobin (HbO2) in the prefrontal cortex (PFC) assessed during active walking. We hypothesized that higher CR would be associated with more efficient brain activation patterns.

Methods: Participants were 55 (mean age = 74.84; %female = 49.1) older adults who underwent the combined walking/fNIRS protocol and had magnetic resonance imaging data. We used an established dual-task walking paradigm that consisted of 3 task conditions: single-task walk (STW), single-task alpha (STA, cognitive task), and dual-task walk (DTW). Using the residual approach, CR was derived from a word-reading test score by removing variance accounted for by sociodemographic variables, tests of current cognitive functions, and a measure of structural brain integrity.

Results: CR moderated the change in fNIRS-derived HbO2 in the PFC across tasks. Higher CR was associated with smaller increases in fNIRS-derived HbO2 from the single tasks to dual-task walking (CR × DTW compared with STW: estimate = 0.183; p < .001; CR × DTW compared with STA: estimate = 0.257; p < .001). The moderation effect of CR remained significant when adjusting for multiple covariates and concurrent moderation effects of measures of gait performance, current cognitive functions, and structural integrity of the brain.

Conclusion: The current study provided first evidence that higher CR was associated with better neural efficiency of walking in older adults.

Keywords: Cognitive reserve; Gait; Neural efficiency; Prefrontal cortex.

Figure 1.

Moderating effects of CR (dichotomized via median split) on the change in fNIRS-derived HbO₂ across task conditions. Light gray indicates high CR; dark gray indicates low CR. Linear mixed-effect model revealed that higher CR (dichotomized via median split) was associated with smaller increases in fNIRS-derived HbO₂ from STW (.273; p = .004; 95% CI: 0.089–0.458) and STA (.335; p < .001; 95% CI: 0.151–0.519) to the DTW condition. STW = single-task walk; STA = single-task alpha; DTW = dual-task walk; CR = cognitive reserve.