Shedding light on the prefrontal correlates of mental workload in simulated driving: a functional near-infrared spectroscopy study

Geissler, Christoph F.; Schneider, Jörn; Frings, Christian · 2021 · Crossref

DOI: 10.1038/s41598-020-80477-w

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Summary

This study investigates the neural correlates of mental workload during simulated driving to identify specific brain regions suitable for future brain-computer interfaces (BCIs) in driver-assisting systems. While excessive or insufficient mental workload impairs driving performance, current objective measures often lack the spatial precision or practicality for real-time adaptation. The authors aimed to pinpoint prefrontal structures sensitive to environmental demands, independent of specific driving maneuvers, using functional near-infrared spectroscopy (fNIRS), which offers greater tolerance to movement artifacts than fMRI or EEG. The researchers employed a within-subject design with 22 participants driving in a high-fidelity simulator. Participants completed two types of experimental tracks: "country" routes with low traffic and simple maneuvers, and "city" routes featuring complex traffic, pedestrians, and dynamic events requiring constant attention and action plan updates. Mental workload was assessed subjectively using the Instantaneous Self-Assessment (ISA) and NASA-TLX questionnaires. Neural activity was recorded via an 18-channel fNIRS system focused on the middle frontal gyrus (MFG). Data were analyzed at two levels: aggregated regions of interest (ROIs) covering anterior and posterior dorsolateral prefrontal cortex (DLPFC) areas, and individual channels for higher spatial resolution. Results indicated that city environments induced significantly higher subjective workload ratings than country environments on both ISA and NASA-TLX scales. Neurologically, all four ROIs showed significantly higher activity during city driving, evidenced by a greater decline in deoxygenated hemoglobin ([deoxyHB]) concentrations. No significant differences were found in oxygenated hemoglobin ([oxyHB]), likely due to systemic artifacts common in motion-heavy settings. Channel-wise analysis revealed six specific channels with significant [deoxyHB] differences, localized to the left MFG, right MFG, and right superior frontal gyrus. Notably, three adjacent channels in the right anterior dorsolateral prefrontal cortex (raDLPFC) showed the strongest activation. The authors conclude that the right middle frontal gyrus, particularly its rostral part, is a critical center for workload-related activity during complex driving. This region’s involvement aligns with its known role in spatial working memory, suggesting that a major component of driving workload stems from the continuous processing and updating of spatial information about the road and other users. The study proposes that the right MFG is a promising target for small-area, economical BCIs that could automatically adapt driver-assisting systems to the driver’s cognitive state, thereby enhancing traffic safety without compromising comfort.

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Topics

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• neuro workload indices
• workload measurement
• mental demand
• cognitive capacity variation
• stress driving

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• Empirical Findings: physiological data
• Methodological Resource: tool software
• Theoretical Contribution: theory or model