NSC during the background AE RR MSD RR LF\HF So β Girls 636 56 0,89 8,4 -0,58 Boys 647 59 0,70 8,9 -0,55 The AE performance required the mobilization of the adaptation resource and alteration of NSC parameters manifested in the reduction of RR-intervals and MSD RR, i.e. in the decrease of pulse variability, the increase of the effect of the sympathoadrenal center of the autonomic nervous system, changes in the contribution of the low-frequency range to the general spectral power and decrease of the fractal ß index. All
24 these changes in preschool children are characterized by dynamics similar to that in adults and teenagers [3, 5]. Differences between boys and girls in these series of the NSC record are not statistically significant. However, ß values in the background AE were significantly higher in girls than in boys (significance level - .036; Student t-test criterion – 2.289). The performance of the AE with a positive reward is accompanied by the increase of group variability of all NSC parameters. In other aspects NSC parameters reproduce NSC values during the background AE. At the same time, there were no significant differences in NSC characteristics between boys and girls. In the AE with a negative reward the LF/HF value was essentially, but not significantly increased as compared to that of the background NSC. In some cases LF/HF value left the optimum range for preschoolers reflecting the increase of the sympathoadrenal activation under the most stressful conditions. Discrepancy in the dynamics of the fractal index and corticolization index-So in boys and girls during the AE with a negative reward (AE -) is worth attention. In girls these parameters increase and in boys they have a tendency to decrease resulting in the appearance of significant differences in ß and So values. Their greatest values are noted in the subgroup of senior preschool girls (β - Student t-test value – 2.392 (p=.022), So - Student t-test value – 2.33 (p=.025)). In girls the most stressful conditions of the verbal activity increase the activation of a higher level of the cardiac pulse control and decrease the chaotization process of the heart rhythm regulation. Effective verbal activity in boys occurs with a decrease of the effect of the higher cortical level and chaotization increase of homeostasis of higher levels of the heart rhythm control by increasing the activity of the sympathetic center of the autonomic nervous system and reducing pulse variability. Best results of the verbal activity in girls of the preschool age are due to more mature processes of the heart rhythm control characteristic of young people as was established in the research of Kamenskaya V.G. and Morozova A.V.  on a group of students.