Fig 1.
a) Experimental setup in the simulator cockpit. b) Scheme of the flight performed by all crews. Pilots departed from Leonardo Da Vinci International Airport (FCO), Rome, Italy and the destination was the Galileo Galilei Airport (PSA), Pisa, Italy. During the cruise phase, an electrical failure was intentionally introduced to the Captain’s instrumentation in order to manipulate the regular execution of the flight. The level of interaction between the two crew members is represented by means of the icons located close to the flight phase symbol (blue → Captain; black → First Officer). The ratio between the size of the two icons describes the presence of an asymmetry in the interaction between pilots (takeoff: asymmetrical interaction between pilots unbalanced towards the CPT who has the control of the aircraft; cruise: symmetrical interaction between the two pilots; landing: asymmetrical interaction between pilots unbalanced towards the FO who took the control of the aircraft after the electrical failure to CPT’s instrumentation).
Fig 2.
Flowchart summarizing data analysis process.
Fig 3.
a) Bar diagram reporting the NASA-TLX sub-scale scores separately for Captains (dark grey) and First Officers (light grey). b) Results of the ANOVA were computed considering as a dependent variable the difficulty perception score and as within factor the FLIGHT PHASES (taxi, takeoff, cruise and landing). The bar diagram shows the mean value for the score assigned to each flight phase by all of the pilots (irrespective of the role). The bars represent their relative 95% confidence intervals. The symbol (*) indicates a statistical difference (Newman-Keuls’ pairwise comparisons) between the flight phases (p<0.05). c) Bar diagram reporting the t-values computed, separately for Captains (dark grey) and First Officers (light grey), on EBR for each flight phase (takeoff, cruise, landing), considering the taxi phase as a reference. The dotted black line represents the statistical threshold for the t-values. d) Diagram reporting the t-values computed, separately for Captains (solid line) and First Officers (dotted line), on the HR-Index for each flight phase (takeoff, cruise and landing) considering the taxi phase as a reference. The symbols (*) and (**) indicate a statistical difference (Newman-Keuls’ post hoc test) between the flight phases and the two pilots, respectively.
Fig 4.
a) Group statistical spectral scalp maps (N = 6) computed, separately for Captains (second and fourth columns) and First Officers (first and third columns), for each of the three flight phases (takeoff, cruise and landing) in the theta and alpha EEG bands. Rendering of the scalp model is viewed from the above (nose pointing downward). The color of each pixel codes for the t-value achieved, for the related electrode, by comparing the spectral activity elicited during each flight phase with respect to the taxi phase (color scale on the right). All of the t-values below the statistical threshold are reported in grey.
Table 1.
Single-subject Connectivity Results.
Fig 5.
Inter-brain connectivity patterns.
Statistically significant connectivity patterns elicited in the theta (3–7 Hz; panel a) and alpha bands (8–13 Hz; panel b) during the takeoff, cruise and landing phases by each pilot couple involved in the study (one couple for each row). The 3D scalp is seen from the above with the nose pointing toward the bottom of the page. Statistical connections between the two pilots’ brains activities are represented by means of black arrows. In the representation of each couple, the first and the second head correspond to the First Officer (FO) and to the Captain (CPT) respectively.
Fig 6.
Results of ANOVA performed on the Interconnections Density index computed on intersubject networks estimated in the theta (panel a) and alpha (panel b) bands, using FLIGHT-PHASE (takeoff, cruise and landing) and COUPLE-TYPE (real and formal) as the main within factors. The bars represent their relative 95% confidence intervals. The symbol (*) indicates the statistical difference between real and formal couples (Newman-Keuls’ pairwise comparisons). The symbols (**) indicates statistical differences between the flight phases for real couples (Newman-Keuls’ pairwise comparisons).
Fig 7.
Bar diagrams reporting the density of connections exchanged between brain macro-areas of the two crew members in the theta (panel a) and alpha (panel b) bands during takeoff (dark grey) and landing (light grey). The inter-areas links density reported here link frontal (FF), central (CC), and parietal (PP) areas of both pilots, as well as crossed connections linking frontal and central (FC), frontal and parietal (FP), and central and parietal (CP) brain areas. The symbol (*) indicates a statistical difference between the takeoff and landing phases (paired t-test, p<0.05).
Fig 8.
Inter-connections Directionality.
Bar diagram reporting the density of connections directed from CPT to FO (panel a) and from FO to CPT (panel b) during the takeoff and landing phases in the alpha band. The symbol (*) indicates a statistical difference between the takeoff and landing phases (paired t-test, p<0.05).