The neuroergonomic evaluation of human machine interface design in air traffic control using behavioral and EGG/ERP measures.

The Air Traffic Control (ATC) environment is complex and safety-critical. Whilst exchanging information with pilots, controllers must also be alert to visual notifications displayed on the radar screen (e.g., warning which indicates a loss of minimum separation between aircraft). Under the assumption that attentional resources are shared between vision and hearing, the visual interface design may also impact the ability to process these auditory stimuli. Using a simulated ATC task, we compared the behavioral and neural responses to two different visual notification designs--the operational alarm that involves blinking colored "ALRT" displayed around the label of the notified plane ("Color-Blink"), and the more salient alarm involving the same blinking text plus four moving yellow chevrons ("Box-Animation"). Participants performed a concurrent auditory task with the requirement to react to rare pitch tones. P300 from the occurrence of the tones was taken as an indicator of remaining attentional resources. Participants who were presented with the more salient visual design showed better accuracy than the group with the suboptimal operational design. On a physiological level, auditory P300 amplitude in the former group was greater than that observed in the latter group. One potential explanation is that the enhanced visual design freed up attentional resources which, in turn, improved the cerebral processing of the auditory stimuli. These results suggest that P300 amplitude can be used as a valid estimation of the efficiency of interface designs, and of cognitive load more generally.

A neurophysiological training evaluation metric for air traffic management.

The aim of this work was to analyze the possibility to apply a neuroelectrical cognitive metrics for the evaluation of the training level of subjects during the learning of a task employed by Air Traffic Controllers (ATCos). In particular, the Electroencephalogram (EEG), the Electrocardiogram (ECG) and the Electrooculogram (EOG) signals were gathered from a group of students during the execution of an Air Traffic Management (ATM) task, proposed at three different levels of difficulty. The neuroelectrical results were compared with the subjective perception of the task difficulty obtained by the NASA-TLX questionnaires. From these analyses, we suggest that the integration of information derived from the power spectral density (PSD) of the EEG signals, the heart rate (HR) and the eye-blink rate (EBR) return important quantitative information about the training level of the subjects. In particular, by focusing the analysis on the direct and inverse correlation of the frontal PSD theta (4-7 (Hz)) and HR, and of the parietal PSD alpha (10-12 (Hz)) and EBR, respectively, with the degree of mental and emotive engagement, it is possible to obtain useful information about the training improvement across the training sessions.

[Conception of a decompression table]. / Conception d'une table de décompression.

After a given time at bottom, different tissues become saturated to different extents with nitrogen. In diving back to the surface a hydrostatic decompression occurs first, followed by the desaturation process some time later. It is during this time interval that all important events are taking place, namely: either a monophasic desaturation, whereby inert nitrogen gas is given off at the alveolar capillary interface. or a biphasic desaturation takes place, giving rise to gas bubbles in the blood-stream as well as in the tissues. We may then encounter pathologies which are benign incidents or, worse, lead to decompression sickness grade II. Since Paul Bert dedicated his thoughts in 1878 to this problem, numerous authors tried to explain this time delay, for trying to suppress it would be entirely unrealistic. Unfortunately, mathematical reasoning has too often overshadowed physiological thinking in these matters. We also stuck to Haldane's concept of 1908, in incorporating Workman's improvements of 1965. This method is based on two main principles: 1. all calculations were done with several "tissues" in mind. Their anatomical boundaries are of no importance as, only their desaturation half-times are relevant. 2. a natural limit is given by the critical saturation-coefficient (CS). It expresses the ratio between the partial pressure of the dissolved gas and the reduction of hydrostatic pressure during ascent (given as pressure gradient). Through experience we were able to put up tables which were more and more safe, in examining foremost the CS ratio and the desaturation times of certain tissues. Several examples are given, the values of which are statistically highly significant, as they incorporate the results of more than 60,000 air dives.

Effects of addition of nitrogen during rapid compression of baboons.

A series of dives was carried out to depths of 600 and 800 m seawater (msw) using baboons (Papio papio). Experiments were designed to study the effects of compression and the use of a He-N2-O2 gas mixture on high-pressure nervous syndrome (HPNS). When N2 was added to the He-O2 mixture at the beginning of a linear compression (200 msw/h), the symptoms associated with HPNS were still seen; in addition, the electroencephalogram (EEG) changes were more severe than those seen without N2. By use of an identical mixture, a 2-h exponential compression to 600 msw produced less severe signs of HPNS than the nonexponential profile. By use of a 2-h exponential compression to 600 msw and with addition of N2 at the end of compression, the HPNS that had been started under the He-O2 mixture decreased. Progressive addition of N2 during compression reduced the behavioral signs of HPNS without further EEG changes. These results show that the action of N2 is more complex than can be explained by a simple narcotic pressure antagonism and that the HPNS differed according to the gas mixture used.