Abstract: BACKGROUND: In daily life, individuals often operate in a dual-task mode that requires simultaneous execution of motor and cognitive functions. This situation necessitates the coordination of both motor and cognitive functions, placing higher demands on brain workload. Theoretically, the difficulty in cognitive tasks can differentially impact dual-task performance. However, the mechanisms underlying changes in prefrontal cortex hemodynamic responses during motor-cognitive dual tasks under varying cognitive loads remain unclear. Elucidating the hemodynamic responses of the prefrontal cortex under different cognitive loads is highly important for optimizing motor-cognitive training intervention strategies and enhancing training effectiveness and safety.
OBJECTIVE: To observe the effects of dual tasks combining narrow-base walking with logical subtraction under different cognitive loads on prefrontal cortex hemodynamics using a portable functional near-infrared spectroscopy device.
METHODS: Thirty college students were recruited to complete three task conditions in random order: narrow-base walking (single task), narrow-base walking with serial-3 subtraction (dual task), and narrow-base walking with serial-7 subtraction (dual task). Changes in oxygenated hemoglobin in the prefrontal cortex, subjective cognitive load levels, and dual-task cost were observed. Spatiotemporal gait parameters were simultaneously recorded for behavioral analysis. After testing data normality with the Shapiro-Wilk test, Friedman test and Wilcoxon test were used to analyze differences in prefrontal cortex activation. Repeated measures analysis of variance was employed to compare cognitive load and gait performance. Pearson correlation analysis was conducted to evaluate the relationship between prefrontal cortex activation and cognitive loads.
RESULTS AND CONCLUSION: (1) Compared with narrow-base walking alone, both dual-task conditions (serial-3 and serial-7) significantly increased multi-channel activation in the prefrontal cortex (P < 0.05). However, activation in the dorsolateral prefrontal cortex was higher under the serial-3 condition than the serial-7 condition (P < 0.05). (2) As task difficulty increased, accuracy rates significantly decreased (P < 0.01), and gait parameters such as step length, stance phase, and swing phase further declined (P < 0.05-0.01), while dual-task cost increased (P < 0.01). (3) Significantly activated channels in the prefrontal cortex were positively correlated with mental demand, temporal demand, effort, frustration, and overall task load, and negatively correlated with task performance. Significant correlations were observed between activated channels in the prefrontal cortex and mental demand, temporal demand, effort, frustration, and overall task load, while negative correlations were found with task performance. To conclude, these findings suggest that selecting a moderate cognitive load during dual-task interventions facilitates adequate activation of prefrontal cortical resources without overloading, thereby achieving a better balance between cognitive and motor tasks. The results reveal the interaction mechanism between motor and cognitive functions in dual tasks, providing scientific support for optimizing the effectiveness and safety of motor-cognitive dual-task training.

Key words: motor-cognitive dual task, functional near-infrared spectroscopy, cognitive load, prefrontal cortex, cerebral hemodynamics