This research studies the effect of long-term cognitive load on developimg fatigue on a range of subjective, behavioural (reaction time) and electrophysiological (individual alpha rhythm), fatigue index parameters in carriers of various polymorphisms of DRD2 genes. Mental fatigue was modeled as a result of continuous cognitive tasks aimed at using attention and working memory for 2.5 hours.
The sample included 51 subjects (male right-handers, the average age - 20 ± 4 years) whose genetic analysis was conducted and polymorphism options of DRD2 gene Taq1A (A1A1, A1A2 and A2A2) were identified.
The research results show that such load significantly affects almost the entire complex of indicators. Significant differences were found between the polymorphisms carriers A1A1 and A1A2 and A2A2 of DRD2 gene polymorphism in the reaction of choice, and also in fatigue index, which reflects the ratio of slow brain rhythms to fast. The results show the positive role of dopamine in developing fatigue.
Group of A2A2 («A1») polymorphism carriers was assumed to show lower fatigue, characterized in SVMR and PB significantly slower reaction time, and before and after long-term cognitive load, compared with carriers of polymorphisms A1A1 and A1A2 (« A1 + «).
Notably, the dynamics of error increase within all polymorphisms is the same, and genotype number of errors does not vary before or after fatigue. The dynamics of reaction time after the exhaustion of all SNPs is approximately the same. This means that polymorphisms are different not only in dynamics of fatigue but physical predisposition to sensory information processing.
The influence of long-term cognitive load on the individual condition (HEM Questionnaire) and also electrophysiological parameters (individual alpha rhythm (IAR), the spectral characteristics of the electroencephalogram (EEG), fatigue index (IS)). Cognitive or mental load was simulated by a series of continuous solutions of various cognitive tasks assigned that were aimed mainly on working memory and attention within the time limit of 2.5 hours. Before and after the test we were making records of background EEG and the participants were completing HEM questionnaires.
Analysis of the results of research conducted by the statistical comparison of the data obtained before and after exercise. The results show that long-term cognitive load significantly tells on the subjective sphere and the activity of the participant. On the electrophysiological level, the load results in a decrease of individual alpha rhythm frequency, a vast increase in the fatigue index, and also the increase of average power of theta, alpha and beta rhythms. Thus, the cognitive load is reflected in the significant shift of brain activity dynamics manifested as quite dynamic parameters of the alpha and beta rhythms power, this being in a more stable performance, such as individual alpha rhythm and the fatigue index. Summing up, a significant mental work leads to a significant increase in the power of slow-wave activity in the brain and the deterioration of the subjective well-being. On the one hand, the results of the research correspond with the literature data and, on the other hand, the results are integrating the data of various studies and consequently provide a more comprehensive view of the process of mental fatigue in terms of the dynamics of the brain.