RELATIONSHIP BETWEEN WORKING MEMORY AND NONLINEAR ACTIVITY OF THE HEART RHYTHM REGULATION SYSTEM UNDER MENTAL STRESS
Mental arithmetic implies the use of cognitive resources and affects the functions of the autonomic nervous system, which has pronounced non-linear properties. Objective. Identification of links between the parameters of the working memory and the nonlinear dynamics of the heart rhythm at rest and under mental stress. Materials and methods. The study involved young healthy men and women - students of the ChGPU named after I. Ya. Yakovlev. Testing of working memory was conducted, as well as ECG recording at rest and mental stress. The ECG analysis was performed using the Kubios HRV program and nonlinear heart rhythm indices ApEn, SampEn, DFA1 and DFA2, D2 were calculated. The complexity analysis was also carried out by us using the RP recurrent diagram with calculation of the average line length (Lmean), maximum line length (Lmax), recurrence level (REC), determinism (DET), Shannon entropy for the distribution of line lengths (ShanEn). Testing the working memory was carried out using the computer package Cognitive Research Tools. Results. There were revealed pronounced statistically significant changes in the nonlinear dynamics of heart rate variability during mental stress, the severity of which depended on the amount of working memory. The initial levels of nonlinear indices of the heart rhythm at rest had a significant impact on the efficiency of performing tasks to determine the working memory.