Using near infrared spectroscopy to detect mental overload in flight simulator
Résumé
Piloting is a complex activity that takes place in a dynamic and rapidly changing environment. In such a context, high level cognitive functions are vital abilities for handling the aircraft, interpreting the instrument parameters, maintaining up-to-date situation awareness and making relevant decisions. These functions, which are traditionally labelled executive functions or cognitive control, are known to involve the prefrontal cortex (Miller & Cohen, 2001), this latter being also involved in decision making in uncertain environment, including navigation task (Yoshida & Ishii, 2006). Despite its impressive complexity, human brain exhibits severe capacity constraints in information processing. Neural basis for such limitations has been showed in various neuroimaging studies (Charron & Koechlin, 2010; Dux, Ivanoff, Asplund, & Marois, 2006). When cognitive functions are overloaded, which is often the case when the context is unfamiliar, uncertain or when time pressure is high, the pilots performance are lessened Durantin et al. 2013). Worst, they may face cognitive tunneling, defined as the inability of the operator to reallocate his/her attention from one task to another (Thomas & Wickens, 2001). In such a situation, it is more likely to commit error and to miss critical information such as visual or auditory alerts. A promising way to detect mental overload is to monitor the prefrontal lobes online. Near infrared spectroscopy is an increasingly popular technique for observing the brain functioning (e.g., Ayaz, 2012). Contrary to more common neuroimaging technique like functional magnetic resonance imaging, it allows in vivo imaging in ecological condition with a correct freedom of movement and in complex environments such as high-fidelity simulators. We used a BIOPAC 16 channel functional near infrared spectroscopy (fNIRS) to monitor prefrontal activity of 10 airline student pilots during two landing phases (easy and difficult) in a flight simulator. In both scenarios, instrument landing system was available to help performing the approach. However, in the easy landing scenario, the external visibility was perfect and there was no crosswind while in the difficult landing scenario, there was no external visibility (dense cloud layer) and there was a strong crosswind. So, the difficult landing condition was supposed to load more heavily on executive functions than the easy one. As expected, results from subjective measurements revealed that perceived cognitive mental effort was higher during the difficult landing. The right dorsolateral prefrontal cortex (DLPFC) was the region that demonstrated the highest concentrations of oxygenated hemoglobin (HBo2) during both scenarios. In addition, fNIRS measurements showed significantly higher right DLPFC concentrations of HBo2 for the difficult landing than for the easy one. In the difficult scenario, the flight performance was strongly degraded in comparison to the easy one. This result demonstrates the sensitivity of fNIRS to detect mental overload in complex and ecological set up. The applications concern online monitoring of the pilot mental workload as well as the evaluation and the certification of new cockpit designs.