Biomarkers of the psychophysiological state during the cognitive tasks estimated from the signals of the brain, cardiovascular and respiratory systems

Diagnostics of the psychophysiological state at rest and under stressful conditions is an important problem. We tested various biomarkers of the psychophysiological state of healthy volunteers at rest and while completing stress-inducing cognitive tasks, namely the Stroop color word test and mental arithmetic test. We tested the biomarkers based on the analysis of electroencephalograms, respiratory signals, and the signals of cardiovascular system. We investigated both the individual characteristics of these signals in the low-frequency range (less than 0.5 Hz), and characteristics of their interaction. According to our results, the most sensitive biomarkers of cognitive task stress are nonlinear phase coherence between the 0.15 and 0.40 Hz oscillations in the respiratory signal and heart rate variability, and integral power of the 0.15–0.40 Hz oscillations in the frontal lobe EEG leads