Investigating mental workload-induced changes in cortical oxygenation and frontal theta activity during simulated flights

Abstract

Monitoring pilots’ cognitive states becomes increasingly important in aviation. Physiological measurement can detect increased mental workload (MWL) even before performance declines. Yet, changes in MWL are rarely varied systematically and few studies control for confounding effects of other cognitive states. The present study targets these shortcomings by analysing the effects of stepwise increased MWL on cortical activation, while controlling for mental fatigue (MF). 35 participants conducted a simulated flight with an incorporated adapted n-back and monitoring task. We recorded cortical activation with concurrent EEG and fNIRS measurement, performance, self-reported MWL and MF. Our results show the successful manipulation of MWL without confounding effects of MF. Higher task difficulty elicited higher subjective MWL ratings, performance decline, higher frontal theta activity and reduced frontal deoxyhaemoglobin (Hbr) concentration. Using both EEG and fNIRS, we could discriminate all induced MWL levels. fNIRS was more sensitive to tasks with low difficulty, and EEG to tasks with high difficulty. Our findings further suggest a plateau effect for high MWL that could present an upper boundary to individual cognitive capacity. Our results highlight the benefits of physiological measurement in aviation, both for assessment of cognitive states and as a data source for adaptive assistance systems.

Assessing the development of mental fatigue during simulated flights with concurrent EEG-fNIRS measurement

“…In HbR, we observed substantial decreases during the first block where MF could not have accumulated yet. Apart from MF, decreases in HbR are also elicited by higher task difficulty 37,42 . The reduced HbR in the beginning of the experiment therefore likely mirrors the learning effect found in subjective ratings.…”

“…Adapted 1-back task. In order to induce constant low working memory load, we used the 1-back condition of the adapted n-back task described in our previous study 37 . The task was programmed in PsychoPy3 v2020.1 49 .…”

“…Recording was performed at 10 Hz with a NIRSport2 with eight sources, seven detectors and eight short-distance channels, in the software Aurora 2021.9 (NIRx Medical Technologies LLC, Glen Head, NY, USA). Further details on the montage design can be found in our previous study 37 . ) is reported.…”

“…We want to contribute to the systematic investigation of MF and MWL. In our previous research, we successfully detected different levels of MWL with concurrent EEG-fNIRS measurement in the flight simulator while explicitly controlling for confounding effects of MF 37 . The current paper is the second step in this systematic investigation and presents an essential expansion of our previous research.…”

“…This time, our aim was to induce MF while controlling for confounding effects of MWL, and to find valid physiological measures to assess it. We induced MF via ToT using a 90-min simulated flight task derived from our previous study 37 . It had a low, constant task difficulty to control for influences of MWL.…”