On using fNIRS in the cockpit: Frontal cortical oxygenation changes as a means of measuring mental workload in simulated flights

Flying an aircraft puts high cognitive demands on the pilot. If the demands exceed the pilot’s cognitive resources, this may lead to errors and severe, if not fatal, consequences. A continuous and objective assessment of mental workload could indicate when to provide assistance to the pilots, even before performance declines. A viable candidate for such an assessment is functional near-infrared spectroscopy (fNIRS). In the present study, we used fNIRS to assess mental workload changes in a flight task. 35 participants completed a 40-minute simulated flight with an incorporated adapted n-back task: The participants had to perform course corrections in accordance with the n-back task in four difficulty levels (0- to 3-back). We assessed n-back performance and oxygenation changes in the dorsolateral prefrontal cortex. Our results show that performance in the n-back task was stable between the 0- and 1-back conditions, then decreased linearly with each higher n-back level. fNIRS data showed a decrease in deoxygenated hemoglobin (Hbr) with increasing n-back level. More precisely, using Hbr, we could discriminate all n-back levels apart from the two highest. We conclude that while fNIRS was not sensitive to higher levels of demand where performance already showed a steady decline, it was indeed sensitive even to slight elevations of cognitive demand that did not yet impair performance. In consequence, fNIRS is a promising method for mental workload assessment and its application in the aviation domain