Key Takeaways & Executive Findings
- •• Cognitive task difficulty does not linearly increase prefrontal cortex activation; a moderate cognitive load optimally activates prefrontal resources. • Excessive cognitive load reduces dorsolateral prefrontal cortex activation, demonstrating a 'cognitive overload' effect. • Moderate cognitive load in dual-task training balances cognitive and motor performance, enhancing training effectiveness and safety. • Prefrontal cortex activation correlates positively with subjective workload and negatively with task performance.
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: narrow-base walking, narrow-base walking with subtracting 3, and narrow-base walking with subtracting 7. Changes in prefrontal cortex oxyhemoglobin, subjective cognitive load, dual-task cost, and spatiotemporal gait parameters were recorded. After Shapiro-Wilk test, Friedman and Wilcoxon tests were used to analyze prefrontal cortex activation differences, repeated-measures ANOVA compared cognitive load and gait performance, and Pearson correlation assessed the relationship between prefrontal cortex activation and cognitive load. RESULTS AND CONCLUSION: Compared with narrow-base walking, both subtracting 3 and subtracting 7 dual tasks significantly increased multi-channel activation in the prefrontal cortex (P < 0.05), but dorsolateral prefrontal cortex activation was higher under subtracting 3 than subtracting 7 (P < 0.05). As task difficulty increased, accuracy significantly decreased (P < 0.01), and gait parameters such as step length, stance phase, and swing phase further declined (P < 0.05-0.01), with dual-task cost increasing (P < 0.01). Significant prefrontal cortex activation channels were positively correlated with mental demand, temporal demand, effort, frustration, and overall task load, and negatively correlated with task performance. These findings suggest that selecting a moderate cognitive load during dual-task interventions is beneficial to fully activate prefrontal cortex 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.
1. Introduction
In daily life, individuals often perform cognitive tasks while executing basic motor tasks, such as walking while conversing, memorizing, or using electronic devices. This simultaneous execution of motor and cognitive activities is termed dual-task. In dual-task situations, individuals must coordinate motor and cognitive functions, placing higher demands on brain workload. Recently, combined motor-cognitive training interventions have been widely applied in rehabilitation practices, including fall prevention in older adults, cognitive impairment, and sports injuries, as they can simultaneously improve motor and cognitive abilities in a single session. In motor-cognitive dual-task interventions, motor intervention methods are relatively mature, while cognitive tasks are typically determined based on the brain regions to be reshaped and their expected activation levels. It is important to note that when the cognitive task exceeds the brain's available resource capacity, task performance and brain activation may not improve linearly; excessively high cognitive load may even induce a decline in both motor and cognitive performance, directly affecting the intervention outcome. The prefrontal cortex is a key region responsible for executive function, attention control, and other higher-order cognitive functions. Therefore, understanding the effects of dual tasks under different brain workloads on the prefrontal cortex is crucial for designing effective motor-cognitive dual-task interventions.
Functional near-infrared spectroscopy (fNIRS) is a non-invasive brain imaging method that can monitor changes in cortical blood oxygenation in real time. Compared with electroencephalography and functional magnetic resonance imaging, fNIRS offers better robustness against motion artifacts and environmental noise, and provides a more comfortable testing experience for participants, making it highly suitable for studying brain activity during movement. It has been widely used in motor and cognitive research across various populations, including infants, students, older adults, occupational groups, and individuals with cognitive impairments. However, the mechanisms underlying prefrontal cortex hemodynamic responses during motor-cognitive dual tasks under varying cognitive loads remain unclear. This study aims to investigate these mechanisms using portable fNIRS, providing evidence for optimizing motor-cognitive training strategies.
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GUO Zhen, LI Shurui, ZHENG Weiwei, LI Ruofei, LI Qingwen (2026). Functional near-infrared spectroscopy analysis of prefrontal cortex hemodynamics during dual tasks under cognitive loads. Chinese Journal of Tissue Engineering Research. https://doi.org/10.12307/2026.21536
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Frequently Asked Questions
What is the main finding of this study?
The study found that cognitive task difficulty does not linearly increase prefrontal cortex activation; a moderate cognitive load optimally activates prefrontal resources, while excessive load reduces dorsolateral prefrontal cortex activation, indicating a cognitive overload effect.
How was the study conducted?
Thirty college students performed narrow-base walking alone, with subtracting 3, and with subtracting 7. Prefrontal cortex hemodynamics were measured using portable fNIRS, along with cognitive performance, gait parameters, and subjective workload.
What are the implications for dual-task training?
Selecting a moderate cognitive load in dual-task training can effectively activate the prefrontal cortex without overloading, thereby improving training effectiveness and safety.
What are the limitations of this study?
The sample was limited to healthy college students, which may restrict generalizability. Future studies should include diverse populations and additional cognitive tasks to explore interaction effects.
What future research directions are suggested?
Future research could incorporate functional connectivity and brain network analysis to understand resource reallocation mechanisms, and expand participant diversity and cognitive task types.
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