[Music-Acoustic Signals Controlled by Subject's Brain Potentials in the Correction of Unfavorable Functional States].

Literature review and the results of own studies on the development and experimental testing of musical EEG neurofeedback technology are presented. The technology is based on exposure of subjects to music or music-like signals that are organized in strict accordance with the current values of brain potentials of the patient. The main attention is paid to the analysis of the effectiveness of several versions of the technology, using specific and meaningful for the individual narrow-frequency EEG oscillators during the correction of unfavorable changes of the functional state.

[EFFECTS OF MUSIC-ACOUSTIC SIGNALS, ONLINE CONTROLLED BY EEG OSCILLATORS OF THE SUBJECT].

The effects of 2 variants of the method of musical EEG neurofeedback, in which the dominant spectral components of subject's EEG (EEG oscillators) are online converted to music-like signals similar by timbre to flute sounds, have been studied. In the first case, these music-like signals were smoothly varying by the pitch and intensity in accordance with the current amplitude of the EEG oscillator. In the second case, the same variations of flute-like sound were accompanied by such musical element as rhythm. After the single exposure, the modifications of subject's brain activity and positive changes in psycho-physiological state of the subject have been found. Particularly pronounced effects were observed under rhythmically organized music-like stimuli.

[Period-tripling in Multiscale Physical and Biological Events].

A recent paper by S.J. Puetz et al. (Chaos, Solitons -& Fractals, v. 62-63, p. 55, 2014) described a fundamental period-tripled model. It involves periods of different astronomical (quasars, Sun), geophysical (geomagnetic, climatic, volcanic) and some biological processes. This work contains statistics for sixteen pairs of a period-tripled sequence. These periods range from -50 years to 1.5 billion years and no signs of the timescale limitations are found. We believe that the universal scope of the fundamental period-tripled model can be used for the development of new methodology of research data analysis: the main idea is that the spectrum of the periods of the studied event should be tested for the similarity with the spectrum of fundamental period-tripling pattern (because of the fundamental nature of the period-tripled model). Using this method, in this study we complement an already described period-tripled model with periods of human memory performance ranging from one minute to one month also adding seven relevant periods/frequencies of the period-tripled model in the range of human hearing. We make a conclusion that these characteristic frequencies may form the basis for music and singing phenomena. The new methodology is particularly appropriate for being applied in medicine and engineering.

[Method of double feedback from EEG oscillators of the patient for correction of stress-induced functional disorders].

Method of correction of human stress-induced functional disorders is proposed which is based on two feedback contours from narrow-band EEG oscillators of the patient. The first one is a usual biofeedback contour in which the feedback signals from the narrow-band EEG oscillator are consciously perceived by the patient and serve him as a guide for voluntary reduction/activation of these EEG components. The second one is an additional contour of resonance stimulation which helps a subject to overcome the difficulties of conscious control of feedback signals. In this contour the parameters of audio-visual stimulation are automatically tuned to the frequency of the dominant narrow-band EEG oscillator of the patient (from the same or other EEG frequency range) to reach its resonance activation. Scientific basis of the method is provided, the results of its experimental testing are presented.

[Utilization of feedback signals from patient's own endogenous rhythms for non-drug correction of human functional disturbances].

The most advanced approach to non-drug correction of human functional disturbances via utilization of feedback signals from patient's own endogenous rhythms, i.e., EEG rhythms, respiratory and heart rate is presented and substantiated. The advantages of its application to biofeedback training procedures are reviewed. Alternative way to utilize the feedback signals through automatic modulation of stimulation parameters by patient's endogenous rhythms is analyzed. The author's own contributions to the field are presented and the most promising ways of further approach development are delineated.

[On the reactions of the human nervous system to complex-frequency optical stimulation]. / O reaktsiiakh nervnoi sistemy cheloveka na kompleksno-chastotnye svetovye vozdeistviia.

A computerized system for precise stimulation and analysis of electroencephalographic (EEG) reactions to two simultaneously presented frequencies of sine-wave light (one constant, 13 Hz, and the other varying from 1 to 6 Hz and vice versa) was used to study the mechanisms of human brain reactivity to complex rhythmical stimulation. The frequencies were generated by computer and presented to the subjects by three different ways: as a result of their simple summation (additively), as a product of their multiplication (multiplicatively, amplitude modulation of constant frequency by the varying frequency), or by separate presentation to different eyes. The dynamics of electroencephalograms for different types of stimulation were compared. Under all three experimental conditions, the dynamics of EEG spectra has demonstrated the same general pattern of resonance activation, which was similar to that observed for the presented signals in the case of their amplitude modulation. Significant positive shifts in the functional state of subjects were observed as a result of stimulation. The results obtained show the leading role of the processes of amplitude modulation in the interaction of integrative, adaptive, and trace mechanisms of the brain functioning during human perception of complex rhythmical stimuli.

[Biofeedback training and human functional state control]. / Adaptivnoe bioupravlenie s obratnoi sviaz'iu i kontrol' funktsional'nogo sostoianiia cheloveka.

Biofeedback (BFB) training paradigm has outstanding place among various approaches to non-phrarmacological human functional state correction. Being an universal way for voluntary self-regulation of physiological functions, it is characterized by efficacy, accessibility and absence of side effects. However, the lack of fundamental knowledge about the BFB mechanisms leads to existence of numerous difficulties and problems that seriously limit the BFB possibilities. Most difficulties seem to concern the problem of adequate choice of BFB type or parameter being voluntary controlled via feedback signals. Some ways to solve this problem are drown on the base of general systems theory. It is shown that BFB procedures could be especially effective in conditions of close interaction between the BFB mechanisms and the central regulatory mechanisms. Such interaction could be reacheb by utilization of certain characteristics of brain electrical activity reflected in the electroencephalogram (EEG). The most perspective seems to be the utilization of discrete narrow band EEG spectral components, individual resonance EEG oscillators or some correlates of human EEG amplitude modulation processes.

[Resonance phenomena to rhythmic light stimulation with various intensity and frequency in human EEG]. / Rezonansnye EEG-reaktsii cheloveka pri ritmicheskikh svetovykh vozdeistviiakh raznoi intensivnosti i chastoty.

The photoinduced resonance EEG response in the occipital area (O1 and O2) of right-handed men during 12-s intermittent photic stimulation was studied as a function of flash frequency (6, 10, or 16 Hz) and intensity (5 levels from 0.05 to 0.7 J). The EEG power in the narrow band coinciding with stimulation frequency was FFT-extracted in 3-s intervals before, during, and after each stimulation. It was found that increase in flash intensity was accompanied by an enhancement of the resonance EEG response and decrease in time of reaching its maximal value. These changes were to a greater extent characteristic for the right hemisphere. The low-intensity stimulation induced more pronounced resonance effects in the left hemisphere, whereas the high-intensity flashes to a greater extent involved the right hemisphere. The asymmetry of the EEG response to stimulation of the middle intensity was slight, and the time of reaching the maximal level of the resonance activation was about 6-8 s. A relatively high level of the resonance EEG response was observed during stimulation with the frequency of 10 Hz, even in case of its minimal intensity. The most pronounced resonance EEG response was induced in the right occipital area by the high-intensity 16-Hz stimulation. The enhanced sensitivity of the right hemisphere to intensity of flashes is interpreted as an indication of interhemispheric differences in nonspecific adaptive mechanisms of the brain.

[The rhythmic structure of the human EEG: the current state and trends of the research]. / Ritmicheskaia struktura EEG cheloveka: sovremennoe sostoianie i tendentsii issledovanii.

During the past decade, spectral analysis has become indispensable instrument for different kinds of EEG processing. With the development of dedicated computer system, investigation of shifts in human EEG rhythm under various conditions has improved considerably. However, it is difficult to make general conclusions from this line of research, since a large number of studies are carried out using the ambiguous experimental approaches and different methods. Present paper aims to evaluate a modern state of the art in the field of human EEG rhythmical structure investigation. The results from recent relevant articles are briefly reviewed according to the universal scheme (EEG rhythm--experimental condition--observed effect). Due to such presentation, the obtained results have been summarized and some tendencies of modern investigations have been revealed. The extension of studied frequency range of rhythmical EEG components to both high (> 35 Hz) and low (< 1 Hz) frequencies, the shift to a more detailed spectral structure analysis simultaneously with ignoring the fixed boundaries of traditional EEG rhythms, the growing attempts to reveal EEG rhythmical structure correlates of cognitive activity, and a wide utilization of dynamic approaches for the analysis of brain electrical activity are discussed in some detail. The observed data are indicate of high functional significance and perspectives of human EEG rhythmical structure investigation.

[Dynamic processes in the human EEG]. / Dinamicheskie protsessy v EEG cheloveka.

The possible mechanisms which determine the temporal dynamics of discrete narrow-band spectral components of human EEG recorded by a single electrode in the state of rest were analyzed. The dynamics of short-segment spectra was observed by application of Fast Fourier Transform (FFT) to 5-s EEG epochs successively shifted by 0.32 s. For each subject the matrices were formed and presented in a graphic mode. Matrix rows represented the number of points in each short-segment spectrum, and the columns represented the number of short-segment spectra. The columns reflect the amplitude dynamics of a given frequency, and power transition between the columns reflects the frequency dynamics. The most common type of the amplitude dynamics consisted in short (2-8 s) periods of stable activity of the discrete spectral components replaced by symmetrical bifurcation or confluence of spectral peaks. The obtained results suggest by the presence of both additive and multiplicative mechanisms of oscillatory interactions in the EEG. More detailed analysis of the amplitude-modulated EEG processes is provided by application of some additive features of the FFT to both EEG and computer-simulated signals.

[The nonspecific mechanisms of CNS adaptation to intermittent stimuli, EEG spectral structure and the optimal parameters of rhythmic sensory actions]. / Nespetsificheskie mekhanizmy adaptatsii TsNS k preryvistym razdrazheniiam, spektral'naia struktura EEG i optimal'nye parametry ritmicheskikh sensornykh vozdeistvii.

Presented paper reviews recent literature data about the role of non-specific mechanisms of central nervous system adaptation and intrinsic properties of organism functional systems in the effects of rhythmical sensory influences. Among the reviewed factors which determine particular effectiveness of relatively weak, but rhythmically organized external signals, there are such as an increased sensitivity of living things to different oscillatory actions, the mechanisms of adaptive reactions, resonance central nervous system phenomena and an interaction of rhythmical sensory stimulation with organism endogenous rhythms. Special attention is paid to endogenous rhythms in the electrical activity of the brain, or to the EEG rhythms. Modern state of art in the field of spectral EEG structure analysis is discussed, and some new approaches to rhythmical sensory stimulation efficacy enhancement based on individual high resolution EEG structure features are delineated.

[The resonance EEG reactions in rhythmical photostimulation and the changes in functional status]. / Rezonansnye EEG-reaktsii pri ritmicheskoi fotostimuliatsii i izmeneniia funktsional'nogo sostoianiia.

Changes in EEG fine structure in the occipital areas, heart rate, and breath pattern were recorded in 10 male volunteers under photic stimulation with slowly varying frequency in the range of lower or higher EEG alpha-subbands. Self-ratings (on the scale SAN-self-assessment of state of health, activity, and mood) of the functional state, general activity, and mood were obtained before and after stimulation. EEG effects of such photostimulation were represented by the resonance EEG responses of discrete spectral EEG components, frequencies of which periodically coincided with varying rate of flashes. Resonance alpha-enhancement levels depended on the initial individual EEG alpha-voltage and stimulation frequency. Average changes in objective and subjective parameters did not differ between the conditions of lower and higher frequencies of stimulation but were significantly different and of opposite signs when the subjects gave higher and lower self-ratings of positive stimulation effect regardless of the stimulation frequency.