The effect of optical stimulation at a frequency of 10 Hz (OS10Hz) on temporal parameters of sensorimotor activity in healthy subjects (n=32) was studied. The expression of the activation response was determined by the ratio of spectral power values (SPα2, μV2) of the high frequency (10-13 Hz) subrange of the α-rhythm of the initial EEG with closed and opened eyes and the frequency of the maximum α-peak (IAPF). A test for simple motor reaction time was performed under normal and OS10Hz conditions. According to the change in the variability of simple motor reaction time (SDSMRT) under OS10Hz compared to the normal conditions, the subjects were classified into two groups: those who showed a decrease (group 1) and those who showed an increase (group 2) in SDSMRT. The subjects of group 1 had significantly higher IAPF (in the O1 lead with eyes closed) and activation reaction intensity (in the O2, O1, P4, P3, and F3 leads) compared to the subjects of group 2. The obtained data suggest that OS10Hz changes the parameters of psychomotor reactions of an individual, and the direction of changes is mediated by individual features of the initial EEG.

Anxiety has a significant impact on the effectiveness of cognitive activity, which may be due to the peculiarities of the organization of voluntary and involuntary attention in individuals with different anxiety. Aim: to examine functional cortical connections in subjects with different levels of trait anxiety in a state of relative rest and when performing an attention test with usage of the coherent analysis of the teta1-band EEG (4–6 Hz). Coherence of teta1-band of EEG was analyzed in subjects (43 people, men aged 19–21 years) with low, medium and high level of trait anxiety (TA, according to C.D. Spielberger) in three experimental situations: the state of relative rest with closed eyes, the initial state before performing the test (with eyes opened) and during the test (red-black tables of F.D. Gorbov). Subjects with high TA in the state of relative rest with their eyes closed had a lower right-hemisphere coherence of the teta1-band EEG in the system of interrelations with focus in the temporal lead. In the initial state, with eyes opened and during test performing, individuals with high TA showed high level of interhemispheric coherence of the teta1-band of EEG. The highest lability of the structure of coherent relationships in the teta1-range of the EEG was observed in subjects with medium TA, who demonstrated an increase mainly in the interhemispheric coherence of most areas of the cortex during the test compared to the initial state. Individuals with high TA were characterized by relative inertia of the structure of coherent relationships in the teta1-range of the EEG at the stages of examination. The results of the study indicate that trait anxiety is one of the factors modulating the organization of neurocognitive networks both in a state of relative rest and during attention testing.

The effect of lateralized optical stimulation with a frequency of 10 Hz on the effectiveness of cognitive task performance (n-back test) was studied in 33 healthy subjects (right-handed men). Test visual information was presented to the right or left visual hemifield under normal conditions and against the background of optical stimulation with a frequency of 10 Hz. The absolute values of the spectral power of the high (10-13 Hz) subrange of alpha-rhythm of EEG (SPα2) were calculated. When test information was sent to the right hemisphere against the background of stimulation, an increase in task performance was revealed in subjects with low SPα2. This was accompanied by an increase in SPα2 in some cortical areas of the contralateral (left) hemisphere and, as a result, an increase in left-side dominance of SPα2. The findings indicate the possibility of using lateralized optical stimulation to improve cognitive task performance, in particular, by changing the interhemispheric asymmetry of the EEG alpha2-rhythm.

Effectiveness of cognitive test “n-back” performing was assessed in 32 subjects, right-handed men, 18—21 years old. EGG was recorded monopolarly in “10—20” system during initial state, in the period after the first learning stage and during the second learning stage while the subjects performed the test on their own. Two groups of subjects were marked, basing on differences between efficiency of their cognitive activity. Spectral analysis revealed none differences in theta-band spectral power between subjects of the two groups at the initial state. Successful subjects demonstrated increase of the theta-band spectral power in occipital, parietal, central and left frontal zones of cortex in the period after the first learning stage comparing to unsuccessful subjects. On the contrary, unsuccessful subjects demonstrated significant increase of the theta-band spectral power in the second learning stage during the test self-performing comparing to the initial state and the period after the first learning stage. Increase of spectral power of the theta-band can be considered as a regression stage of systemogenesis, accompanied by increase of the representation of low-differentiated systems in new behavior realization and causing high efficiency of cognitive activity.

We studied the effect of optical stimulation with a frequency of 10 Hz on the cognitive task effectiveness (the “n-back” test) and spatial characteristics based on the coefficients of coherence (Coh) of the general, high, and low ranges of the EEG alpha rhythm in healthy subjects (38 men aged 18-26 years). Based on the performance of the test presented in the optical stimulation absence, groups with high (group 1) and low (group 2) results have been identified. It was found that the optical stimulation led to a decrease in the test effectiveness in group 1 subjects and to an increase in group 2 persons. Optical stimulation increased interhemispheric integration of neural ensembles in a number of cortical areas at frequencies of a high subrange of the alpha rhythm. An increase in interhemispheric cooperation was more characteristic of subjects who increased the test activity effectiveness against the optical stimulation background. It is assumed that the growth of interhemispheric integration caused by rhythmically organized 10-Hz optical stimulation is a factor contributing to an increase in the effectiveness of performing cognitive tasks of this kind.

Noninvasive methods of transcranial stimulation in clinical and research activity have become widely applied for the last few years. Due to the high spatial and temporal resolution, these methods allow to explore oscillatory processes that underlie important cognitive functions on a new level. In particular, researchers got an opportunity to influence rhythmic processes, which provide function of attention by these methods. By the way, stimulation of different brain zones with theta-rhythm frequency appears to be interesting, as far as oscillations of attention on this frequency reveal itself both in external activity of subject and in oscillatory activity of neurons and neural ensembles. Aim – analysis and summarize of domestic and foreign researches with usage of transcranial stimulation method to identify role of theta-rhythm in attention processes. Analysis of modern data concerning significance of theta-rhythm in organization of attention processes was performed analyzed. Different modes of transcranial stimulation methods, that allow to discover fundamental role of theta-rhythm in oscillatory activity of neural assembles, which are the base for attention mechanisms were considered. The review noted that the method of transcranial magnetic stimulation (TMS), which is based on the principle of electromagnetic induction with potential excellent temporal and sufficiently decent spatial resolution, is extensively widely used. Usually, TMS is performed with usage single-pulse, paired-pulse, or repetitive rhythmic stimulation. In current review special attention is salaried to the theta burst stimulation protocol. It was suggested that current protocol hypothesizes to influence brain plasticity and simulates the effect of theta-gamma coupling, which is to change the amplitude of the potentials at the frequency of the gamma rhythm depending on the theta wave phase. During the applying of the TMS different variants, several research methodological approaches were applied. Thus, usage of TMS may disrupt functioning in certain cortex areas , also it is possible to increase the oscillatory activity of a particular region at a particular frequency and to enhance or decrease the synchronization of remote cortical areas in a certain frequency range. These approaches may be used directly during the execution of the test task by the subjects or in the period prior the test performing. Many researches show that transcranial stimulation of some zones of cortex contributes to the achievement of better results of examinee in tests on memory and attention. This effect is most often observed while usage of stimulation with theta-rhythm frequency. Improvement of memory and attention functions has high practical meaning for wide range of activity. Understanding of regularities and mechanisms of stimulation with theta-rhythm frequency would allow to create systems and protocols of stimulation, which would effectively improve these functions for the long period.

At present time conceptions of complex neurophysiological mechanisms underlying processes of attention are actively developing. In last few years, several researches revealed rhythmic character of processes of attention. Especially theta-rhythm is considered to be significant in organization of rhythmic interactions between brain zones, which take part in providing attention systems work. The aim of the work – to analyze and summarize modern date about role of theta-rhythm in providing basic processes of attention. The report presents modern data about role of theta-rhythm in processes of attention. Specific features of attention systems are discussed. Thrifold model of attention, developed by Steven E. Petersen and Michael I. Posner is reviewed in detail. Moreover, evidences of rhythmic character of processes of attention are summarized and leading part of theta-activity in providing these processes is demonstrated. We also discuss the investigations by Randolph F. Helfrich and Ian C. Fiebelkorn et al. which stated that the quantization of processes of attention with theta-frequency as a general principle of brain structures activity. Dependence of frequency characteristics of cortex zones of human brain from number of objects of attention is discussed. There is also an analysis of theta-band’s ability to modulate biopotentials of higher frequency. Special attention is paid to the researches focused on theta-gamma coupling. The influence of theta-rhythm phase on gamma-rhythm amplitude in phase-amplitude coupling of theta- and gamma-band is analyzed. Theta-rhythm is considered to be one of the rhythmic components that regulate complex mental functions such as attention, memory and consciousness. Obviously, there is a lack of an exact understanding of the role for every band in mental functions regulation; therefore, more investigations in this field are required. However, several data about the role of theta-band in mental functions was collected. A complex of systems with different physiological and neurochemical basis provides attention. It was demonstrated that attention - is a rhythmical process in which theta-band is a crucial part. Theta-rhythm provides synchronization and joint activity of distant brain structures. Moreover, theta-rhythm modulates high-frequent bands. Theta- gamma-band coupling is supposed to be important for attention. Such cooperation is considered to be an evidence of cortical and subcortical zones and provides coordination of analyzing systems of different level. It is suggested that different phases of theta-band may provide retention/switching of attention or determine information flow. As a summary of review of literary sources, there is a conclusion about high significance of this frequency range in different attention systems functioning.

EEG spectral power (θ1-, θ2-, α-, β1- and β2-ranges) was studied in subjects (n = 43, men, aged 18–21 years) with various trait anxiety levels during attention testing. Trait and state anxiety levels were assessed according to Spielberger prior to testing. In the initial state with the eyes open, subjects with low trait anxiety demonstrated significantly higher power of the EEG θ1- (in the occipital and left parietal cortical regions) and θ2- (in the left frontal and right temporal regions) bands than those with high anxiety level. At the same time, lower power of the EEG α-band (in the left central and frontal regions) was observed in subjects with high trait anxiety level, comparing to those with low anxiety levels. During the test, subjects with low anxiety demonstrated significant increase of spectral power in θ1- and β2-EEG frequency ranges in all areas of the cortex (except for the temporal region) compared with the preceding periods (with the eyes open). The increase of spectral power in the EEG θ1-band was also found in subjects with high trait anxiety level during the test. However, there was no intensification of β2-rhythm of the EEG. One can assume that the revealed patterns of EEG index dynamics reflect the domination of either orienting or defensive component in the motivational structure of subjects with different trait anxiety levels.

We studied the effect of optical stimulation (10 Hz) on the effectiveness of mnestic activity in the n-back task in healthy subjects ( n= 32). EEG was recorded at all stages of the examination. The absolute values of the spectral power of the 10 Hz frequency (μV2) of the alpha range were calculated. According to the results of the test without optical stimulation, the examinees were divided into groups with high (group 1) and low (group 2) task performance. In the initial state, the spectral power of 10 Hz was significantly higher in group 1 subjects. Under conditions of screen flickering, the results became poorer in group 1 and better in group 2 in comparison with the results under normal conditions. These changes were accompanied by an increase in the spectral power of 10 Hz only in group 2 subjects. These findings can provide the basis for the development of practical recommendations for improving the mnestic functions in patients with consideration for the individual characteristics of their initial EEG.

Changes in the power and coherence of the EEG theta-1 (4-6 Hz) and theta-2 (6-8 Hz) activity were studied in subjects (31 males, 18-21 years old) with different performance levels in logical tasks. EEG was recorded to the International 10-20 System from the occipital (02, 01), parietal (P4, P3), central (C4, C3), frontal (F4, F3), and temporal (T4, T3) leads. The achievement of better performance during the tests based on logical reasoning positively correlated with higher spectral power of theta-1 band potentials in the left cortical areas. The theta-1 band potential power increased during testing and compared to the previous period in the left occipital, parietal, central and temporal cortical areas. The simultaneous increasing in intrahemispheric coherence of theta-1 band potentials was observed in the left frontal and central areas, as well as in the left frontal and parietal cortical areas. The spectral power of theta-2 band potentials decreased during testing and compared to the previous period in the right central frontal and temporal cortical areas. The inter- and intrahemispheric coherence of the EEG theta-2 band potentials decreased during testing in the system of relationships with the focus in the left and right occipital and right parietal cortical areas. The desynchronization in the EEG theta 2 band in all cortical areas was observed at transition from a state of quiet wakefulness with eyes closed to a state with eyes open. The conclusion is made about the different functional significance of the electrical activity of the low and high frequency theta EEG bands under cognitive activity.

У испытуемых (n = 43; мужчины 19-21 года) исследовали пространственные характеристики тета-активности и результативность когнитивной деятельности с переключением внимания, которая моделировалась при помощи компьютеризованного теста Горбова-Шульте (красно-черные таблицы) в условиях голосовой помехи. По изменению результативности деятельности в условиях слуховых помех выделены группы устойчивых к помехам (n = 17) и неустойчивых к помехам (n = 18) испытуемых. Анализ когерентных взаимоотношений тета-потенциалов ЭЭГ на разных этапах обследования выявил определенную топографическую сеть функциональных связей по тета-ритму, объединяющую височные, центральные и фронтальные зоны коры головного мозга с локализацией фокуса этих связей в левой височной области. В исходном состоянии у помехоустойчивых испытуемых в отличие от помехонеустойчивых уровень функционального взаимодействия на основе тета-потенциалов между входящими в эту сеть областями был значимо ниже. При выполнении тестов у устойчивых к помехам испытуемых в отличие от помехонеустойчивых наблюдалось значимое увеличение кооперации в тета-полосе между областями коры в пределах выявленной топографической сети. Обсуждается роль тета-ритма в функциональном объединении структур мозга при выполнении когнитивной деятельности с переключением внимания.

We studied the dynamics of spectral coherence characteristics of the EEG θ-, β 1 -, and β 2 -activity and the heart rate variability (HRV) in subjects performing cognitive tests. We found an association between the HRV parameters in the process of cognitive activity and the coherence of potentials in the EEG θ-, β 1 -, and β 2 -bands. The heart rate parameters in the baseline state and during the test performance best correlated with the levels of the right-hemispheric coherence of potentials in the θ-, β 1 -, and β 2 -bands of the baseline EEG (eyes closed). The higher coherence levels corresponded to lower values of the mean time of RR intervals ( RRNN ), coefficient of variation (CV), total power (TP), the power of the high-frequency (HF) and low-frequency (LF) components in the HRV spectrum. During the performance of the test, higher coherence values in the EEG θ-bands with the focus in the right temporal lead corresponded to higher LF/HF values reflecting the predominance of sympathetic effects on heart rate.

The spatial organization of the EEG β2 rhythm was studied in subjects with different ratios of speed and accuracy of reproduction of sequences of signals on a monitor screen. Students with high accuracy and speed of task performance were characterized by high levels of lability of coherence interactions in the EEG β2 rhythm, apparent as higher levels of coherence during the memorization and reproduction of sequences than in the initial state. Conversely, the structure of coherence connections at the activity stages in individuals performing the task slowly and with errors showed no significant change.

Changes in the power and coherence of α-activity and heart rate variability (HRV) were studied in students with different performance levels in logical tasks. In those students who reached high scores in the cognitive tests, we observed higher lability of α-activity and HRV; the values and their ratios varied among the stages of intellectual activity. In these subjects, a decrease in the spectral power of α-band was more pronounced than in other groups. We also observed changes in the interhemispheric coherence and in the structure of coherent interactions in the α-range at different stages of task performance. In contrast, the number and structure of coherent interactions in individuals who showed lower results did not significantly vary at different stages of task performance. As compared with this group, the students with higher test results showed a more pronounced decrease in the total spectral power (TP) and an increase in the low frequency/high frequency (LF/HF) ratio which returned to the initial level after the end of the tests. In students with better results in these cognitive tests, the dynamics of RRNN, TP, HF, and LF/H F during task performance correlated with the dynamics of interhemispherical α-band coherence.