## 4 Discussion  
The purpose of this study was to evaluate the neurophysiological effects of VR during multitasking CT in healthy subjects and the acceptability and feasibility of the original protocol VR multitasking CT in both a healthy group and cardiac surgery patients. Our findings indicated that the healthy individuals demonstrated an increase in psychomotor speed, higher attention indicators, as well as higher mental rotation test scores after completing one session of VR multitasking CT. Additionally, there was a decrease in the missed signals in the executive function test. The assessment of the influence of VR on the human psychophysiological state is ambiguous, and the data obtained by different authors are often contradictory [23; 41; 42]. According to [PERSON] and her co-authors [41], a higher cognitive load in VR is linked to reduced long-term motor memory formation. In another study, it was shown that healthy individuals were able to successfully adapt to visual-motor rotation [43]. According to our data, healthy subjects can easily adapt to virtual environments because their psychometric indicators improved after VR training. In addition, the healthy subjects considered the task to be easy to complete. Thus, the developed VR paradigm demonstrated acceptable subjective difficulty and tolerability among these participants. The analysis of the changes in the EEG indicators after the VR experiment revealed that the theta 1 power decreased compared to the baseline values. It should be noted that the alpha 1 and alpha 2 rhythm power increased. Therefore, the theta/alpha ratio decreased. EEG patterns are among the current methods of neuroimaging that directly reflect the electrical activity of the brain at the level of synapses in real-time. The rhythmic activity in the brain is divided into five main types: delta rhythm, theta rhythm, alpha rhythm, beta rhythm, and gamma rhythm [44]. In the context of this study, the changes in theta and  
Figure 5: The results of the SUS (**a**) and SMEQ (**b**) scales in the cardiac surgery patients: in the subfigures, the mean scores and minimum-maximum of appropriate scales are shown. alpha rhythmic activity provided the most important information about the status of the participants in the VR experiment. Theta rhythm can be detected in the waking state and increases with emotional arousal, fatigue, and drowsiness [45; 46]. The power increase in theta activity in the resting-state condition may be considered as a correlate of brain dysfunction [4; 37]. A recent study showed that fatigued participants with brain damage who performed a VR balance task demonstrated an increase in the theta power [46]. As demonstrated by our data, VR multitasking training resulted in a decrease in theta power in the healthy subjects. We suggested that the cognitive workload was acceptable, with low subjective difficulty, and caused activation of adaptive processes in the brain. Alpha rhythm (8-13 Hz) is the main rhythm of the brain, which is recorded in healthy people in the occipital-parietal regions of the brain with closed eyes in a state of calm wakefulness and rest. A decrease in the power of the alpha rhythm is an indicator of cognitive impairment [44]. Previous studies using the EEG method to estimate brain correlations of cognitive load reported that multitasking activity can lead to an increase in alpha power [47]. An increase in alpha power is also caused by monotonous activity. The younger participants showed markedly increased alpha activity during a short (4-5 h) working shift in the post office [48]. The EEG changes in the subjects after VR in our study are in line with previous investigations. A decrease in the theta/alpha ratio is a sign of domination of the alpha activity and reduced levels of theta power [44]. All of this together corresponds to patterns of the optimization of brain activity under the influence of monotonous mental activity. A positive evaluation of VR multitasking training in cardiac surgery patients was another significant result of our study.