Combination of EEG-Guided Adaptive Neurostimulation with Resonance Scanning in Correction of Stress-Induced States and Cognitive Rehabilitation of University Students

The correction of stress-induced states and cognitive rehabilitation were carried out during the examination session in three university student groups comparable in the number, sex, and age. In the experimental group, a combination of EEG-guided adaptive neurostimulation with preliminary resonance scanning was used. In control group 1, only EEG-guided adaptive neurostimulation was used. In control group 2, musical-acoustic stimuli were presented without feedback from the subject's EEG. Experiments with preliminary resonance scanning revealed the maximum positive effects compared to the two control types of stimulation. A significant increase in the power of EEG rhythms, especially in the alpha range, was accompanied by a significant increase in subjective indicators of the functional state and cognitive activity. These results can be explained from the standpoint of the progressive involvement of the resonant, integrative, and neuroplasticity mechanisms of the brain into the processes of normalization the functional state of the body under the influence of combined stimulation procedures.

Correction of Stress-Induced States Using Sensory Stimulation Automatically Modulated by Endogenous Human Rhythms

This article considers the dynamics of the development of a potential approach to correcting stress-induced states in humans, i.e., adaptive neurostimulation. The approach consists of presenting sensory stimulation automatically modulated by intrinsic rhythmic human processes such as the respiratory rhythm, the heartbeat rhythm, and electroencephalograph (EEG) rhythms. Many examples have shown that real-time self-adjustment of the stimulation parameters by these rhythms leads to a high level personalization of therapeutic stimulation and increases in its efficacy in suppressing stress-induced states. The publications reviewed here point to the advantages of this approach for developing innovatory technologies using complex feedback from endogenous human rhythms to correct a wide spectrum of functional disorders.

[Music therapy procedures controlled by the brain potentials in treatment of functional disorders]

Twenty years ago, the Korsakov's Journal of Neurology and Psychiatry has published the article of Ya.I. Levin 'Brain music in the treatment of patients with insomnia'. This publication was the starting point for an innovative approach to preventing and correcting functional disorders of a person via musical or music-like stimuli that are controlled by the brain potentials of patient's. This approach called 'Music of the brain' is fully consistent with modern ideas about preventive neuroscience as a new field of scientific research at the intersection of neuroscience and preventive medicine. In this review, the authors analyze initial studies on the effects of music on the brain and discuss their limitations. To increase the effectiveness of the approach, a unique combination of musical therapy with the neurofeedback method, the technology of musical neurofeedback, has been developed. Results of the application of developed technology for treatment of human functional disorders are presented, and promising directions for further research are outlined.

[Attention deficit hyperactivity disorder and current possibilities of its treatment by the method of neurofeedback training]

The article provides an overview of the literature data for the past 10 years on the prevalence, specificity of manifestations and approaches to the treatment of attention deficit hyperactivity disorder (ADHD). The current data on the nature and mechanisms of the method of neurofeedback training (NFBT), as well as the available data on the use of the method for treatment of ADHD are presented. The evaluation of the effectiveness of existing variants of the method in the treatment of ADHD is given, and promising areas for further research are identified.

[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.

[Music therapy and "brain music": state of the art, problems and perspectives]

Recent literature on the problem of interaction between music and the brain is reviewed and summarized. Mechanisms and effects of two most popular music therapy applications are picked out, including music listening and music making. Special attention is paid to relatively new line of investigations that is called "music of the brain" and deals with transformation of bioelectric processes of human organism into music. Unresolved questions of music therapy are identified and some promising lines of future investigations are delineated.

[Modern non-drug approaches to human sleep regulation]

Existing approaches to non-drug regulation and induction of human sleep are analyzed with an attempt of their classification. The main attention is paid to the methods that utilize modern computer technologies of registration and analysis of various characteristics of human organism functioning, basically to the electroencephalogram (EEG). Normal human sleep EEG correlates and their changes during different sleep stages are reviewed. Modern opportunities to regulate and induce human sleep via utilization of different EEG characteristics are analyzed.

[Modern approaches to human cognitive activity enhancement]

Recent literature on human cognitive activity enhancement is reviewed and summarized. Two classes of pharmacological approaches are picked out, i.e. modern aspects of traditional substance utilization and application of specially developed drugs. Among non-pharmacological approaches a number of psychological, physiological, behavioral and biophysical methods to improve human cognition, memory and learning are analyzed. The most attention is paid to non-drug approaches that utilize bioelectric processes of the individual including characteristics of its brain electrical activity--electroencephalogram (EEG) to enhance different aspects of cognitive functioning. Some promising lines of these investigations are delineated.

[On efficiency of biomanagement with negative feedback from patient's EEG in correction of functional disorders, caused by stress]

The perspective approach to non-pharmacological correction of the stress induced functional disorders in humans, based on the double negative feedback from patient's EEG was validated and experimentally tested. The approach implies a simultaneous use of narrow frequency EEG-oscillators, characteristic for each patient and recorded in real time span, in two independent contours of negative feedback--traditional contour of adaptive biomanagement and additional contour of resonance stimulation. In the last the signals of negative feedback from individual narrow frequency EEG oscillators are not recognized by the subject, but serve for an automatic modulation of the parameters of the sensory impact. Was shown that due to combination of active (conscious perception) and passive (automatic modulation) use of signals of negative feedback from narrow frequency EEG components of the patient, opens a possibility of considerable increase of efficiency of the procedures of EEG biomanagement.

[Characteristics of EEG-based biofeedback treatment procedures in normal and complicated pregnancy]

Electroencephalographic characteristics during the application of EEG-based biofeedback treatment procedures for non-drug correction of functional disturbances were compared in pregnant women with normal and complicated pregnancy. As compared to normal-pregnancy group, in the abortion-threat group, the initial EEG data were characterized by a significant reduction of alpha-rhythm at the expense of theta and beta enhancement. Average number of successful attempts to voluntary regulate the EEG rhythms was significantly reduced in the abortion threat group (55.4 +/- 4.7%) as compared to the normal group (70.2 +/- 5.0%). The least efficiency was observed for EEG beta-reduction procedures. All patients demonstrated significant positive changes in self-estimated values of health and mood. However, though the anxiety level significantly decreased in the group with normal pregnancy, it increased in the abortion-threat group. Thus, the EEG-based biofeedback procedures were shown to be an effective supplement to conventional methods of complex therapy of pregnancy complications, but they required taking into consideration the EEG and subjective features of the patients in case of complicated pregnancy.

[Stress, the consequences of its influence on humans and modern non-drug methods of its correction]

Recent literature on different kinds of stress and its behavioral, physiological and medical consequences for humans is reviewed and summarized. Modern non-drug approaches to prevention and correction of stress-induced functional disturbances in humans are analyzed, traditional and instrumental methods of anti-stress therapy are reviewed. The most attention is paid to the approaches that utilize human brain electrical activity characteristics reflected in the electroencephalogram (EEG).

[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]

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]

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.

[Photoinduced resonance phenomena in the human electroencephalogram as a function of frequency, intensity, and duration of stimulation]

The features of resonance phenomena in high-resolution EEG structure were analyzed for two intensities and three values of duration of exposure to 20 constant frequencies of intermittent photic stimulation in a range of 1-20 Hz with 1 Hz steps. It was shown that with a 6 s step duration, an irregular activation of multiple spectral EEG components for both light intensities occurs. With longer durations (12 and 18 s) of fixed-frequency stimulation, the EEG reactions are of resonance nature. Low-intensity flashes cause only the resonance activation of the intrinsic oscillator in the range of dominant alpha-EEG frequency. During a more intensive stimulation, the resonance EEG phenomena are observed for the whole range of stimulation frequencies. The interval of 6-12 s is supposed to be the relaxation period for a system of brain electrical activity generation. After this time, the low-intensity stimuli cause the adaptation of the system to light, whereas more intensive flashes cause more pronounced resonance EEG phenomena and physiological effects.

[Resonance phenomena to rhythmic light stimulation with various intensity and frequency in human EEG]

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.

[Dynamic processes in the human EEG]

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 rhythmic structure of the human EEG: the current state and trends of the research]

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.

[The nonspecific mechanisms of CNS adaptation to intermittent stimuli, EEG spectral structure and the optimal parameters of rhythmic sensory actions]

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.

[Endogenous body rhythms as a modulating factor for parameters of stimulation]

The supposition about increased efficiency of sensory stimulation in the case of feedback control of its parameters by patient's own endogenous rhythm is experimentally tested. Transcutaneous electric nerve stimulation with parameters being feedback controlled by patient's respiratory rhythm was used as a model in 12 male volunteers suffering from different ethiology pain. Significant activation of low frequency (8 divided by 10 Hz) alpha electroencephalogram components, deepening of breath, the decrease of both muscle tension and galvanic skin response amplitudes, as well as pronounced pain relief effects together with increase of functional state and mood levels were the results of such transcutaneous electric nerve stimulation modification.

[The resonance EEG reactions in rhythmical photostimulation and the changes in functional status]

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.

[The dynamic and regional characteristics of the high-resolution EEG structure in voluntary activity]

For revealing the dynamics of interrelations between EEG components having stable tuning to individually determined frequencies a dynamical high resolution EEG structure analysis was used. There were three successive experimental stages: rest, motor reproduction of time interval and tapping. Significant increase of EEG components intercorrelations for the right frontal area, minimal number of significant relationships between EEG and movement temporal characteristics, and the occurrence of hemispheric asymmetry in the number of EEG-movement correlations were observed for time reproduction task. This task specifics and the possibilities of used approach for precise functional states differentiation are discussed.

Stability of resonance EEG reactions to flickering light in humans

In order to study resonance phenomena in the EEG response to flickering light, 10 subjects were exposed to intermittent photic stimulation with the frequency of flashes linearly changing from 1 to 15 Hz and vice versa. Spectral analysis of occipital electrical activity revealed the occurrence of peaks of spectral density in those frequency components which coincide with the frequency of flashes. Such resonance peaks were observed at individually specific frequencies of stimulation. To assess the stability of the characteristics of the resonance phenomena, a repeated trial with 4-fold higher rate of changing the flash frequency was performed 3 months later. In a repeated trial the resonance phenomena were less pronounced, but were registered at the same frequencies as in the initial trial, showing significant test-retest reliability. The data obtained are interpreted in terms of provoking the activity of multiple brain oscillators having a narrow tuning to individually specific frequencies of photic stimulation by flickering light with the changing frequency of flashes.

Electrical activity of the cortex and reaction times to auditory signals and light stimuli

We investigated the electrical activity of the occipital, sensorimotor, and frontal zones in the right and left hemispheres of the cerebral cortex and times for bimanual motor response in healthy adult experimental subjects between the ages of 15 and 25 receiving photostimulation by means of pulse trains with frequencies increasing from 15 to 25 Hz and pulse trains with frequencies decreasing from 15 to 5 Hz. We observed nonspecific physiological reactions in the organism regardless of the type of photostimulation presented and also observed specific reactions dictated by the parameters of the light stimulus acting upon the brain. It was demonstrated that the action of the light was most effective when the frequency of the stimuli was gradually increased. The expressiveness of the alpha-band of oscillations in the electrical brain activity increased in this case, and the asymmetry of the bimanual motor responses changed significantly. A definite connection was noted between the physiological reactions of the experimental subjects and their subjective states.

[Effect of intermittent photostimulation of varying frequency on the formation of trace processes and spectral components in the human EEG]

The EEG of occipital areas was recorded in adult healthy male subjects on presentation of haphazardly alternating intermittent light stimuli with frequencies varying from 15 to 5 Hz and from 15 to 25 Hz every 5 sec. Two groups were distinguished in respect to a greater or lesser domineering of the main frequency band of the range. Dynamic spectral analysis revealed obvious shifts of the EEG spectral composition in respect to the background under the effect of the stimulation, an enhancement of different bands of the range in light flickering, and the suppression of the EEG trace responses to the time in the EEG range coinciding in frequency with the frequency range of the photostimulation. The above changes were mainly characteristic of the 2nd group of subjects and mostly of the left hemisphere of the brain.

[Electrical activity of the cortex and reaction time to photic and acoustic stimuli]

Grown-up subjects revealed both unspecific and specific bimanual motor responses to photostimulation with growing and declining frequency. The former mode of stimulation proved more effective. A relation was found between the physiological responses of subjects and their subjective condition.

[Dynamics of the formation and interrelationship of trace phenomena in 6--7-year-old children]

The dynamics of formation, the reproduction characteristics and interrelation of trace phenomena in conditions of a stable vs. unstable pause between the stimuli in Konorski test were studied in 148 6--7 year old children. It has been shown that with a stable interstimuli pause, along with correct voluntary reactions, based on stimuli traces, two types of electropgraphic trace reaction to time are elaborated--anticipatory and post-stimulatory. In this case trace phenomena are formed much more rapidly and their connection with the volume of the children's short-term memory is tighter than in experiments with an unstable interstimuli pause. It has been also shown that children's school resluts significantly correlate with the caracteristics of their mnemic activity--the volume of the short-term memory and Konorski test data.