Processing and model design of the gamma oscillation activity based on FitzHugh-Nagumo model and its interaction with slow rhythms in the brain

The brain is processing information 24 hours a day. There are millions of processes proceeding in it accompanied by various spectra of rhythms. This paper tests the hypothesis that the slow delta rhythm excites the gamma rhythm oscillations. Unlike other papers, we determine the slow rhythm spectrum not at the hypothesis stage but during the experiment. We design algorithms of filtering, envelope extraction, and correlation coefficient calculation for signal processing. Moreover, we examine the data on all electroencephalogram channels, which allows us to make a more reasonable conclusion. We confirm that a slow delta rhythm excites a fast gamma rhythm with an amplitude-phase type of interaction and calculate a delay between these two signals equal to about half a second.

Dissociation and Brain Rhythms: Pitfalls and Promises

Recently, Vesuna et al. proposed a novel circuit mechanism underlying dissociative states using optogenetics and pharmacology in mice in combination with intracranial recordings and electrical stimulation in an epilepsy patient. Specifically, the authors identified a posteromedial cortical delta-rhythm that underlies states of dissociation. In the following, we would like to critically review these findings in the context of the human literature on dissociation as well as highlight the challenges in translational neuroscience to link complex behavioral phenotypes in psychiatric syndromes to circumscribed circuit mechanisms.

Study of the Combined Effect of Stress Factor and Musical Signal on the Psychophysical State of Human

Today the actual direction in psychoacoustics is the use of acoustic influences in order to correct the physiological, functional or psychological state of man. Various audio stimuli are used to achieve this goal, such as regulating heart rate, increasing the productivity of human work, improving mood and relieving depression. To study the effectiveness of music therapy with the help of modern electroencephalographic complexes, an electroencephalogram (EEG) is recorded and analyzed. Changes in the state of the brain can be assessed by changes in the frequency components (rhythms) of the EEG. Delta rhythm is registered during deep sleep, hyperventilation or anesthesia. The dominance of delta activity in adolescents and adults in the state of wakefulness is a sign of pathology. There is information that fluctuations in this rhythm can be identified in the EEG signal at rest under some forms of stress. The aim of this work is to analyze the ratio of the contribution of delta waves of the brain in its total activity in percentage when listening to low-frequency acoustic signals before and during the action of stressors. The experiments were conducted on 5 people, of whom 2 were men and 3 – women, all of them aged 18-22 years. A total of 14 experiments were conducted - 7 in male and female groups. Electroencephalogram (EEG) registration took place in 16 leads. The composition “Demon Wings” by Bohren & der Club of Gore was used as a musical impact factor. Research was conducted in time periods before and during the increased study load, which is actually considered as a factor that causes an increase in psycho-emotional stress. The results obtained in the periods before and during the influence of the stress factor are presented via the following data: mean values ​​of the comparative levels, differences in mean values and the probability of error of the delta rhythms in the two hemispheres of the brain in periods during the first and third minutes of the experiment. The probability of error of the assumption was determined via using Student's t-criterion. Obtained results show that the average values ​​of the test groups under the influence of stress factor increased significantly relative to the values ​​obtained before this influence. In addition, if before the influence of stress factors there was a decrease in values ​​in the third minute of the experiment relative to the first, then after this effect, the values ​​did not vary. There is no statistically significant difference for the last two compared groups The data presented in the paper indicate that the level of delta rhythm increases significantly during the indirect influence of time-stretched stressors, despite the presence of another type of influence - acoustic, caused by a low-frequency music signal. This rhythm is abnormal for the human body, which is in good spirits. That is why the presence of a high level of this rhythm can affect the accuracy of experiments that investigate the effect of a musical signal on the psycho-emotional state of a person, regardless of the nature of the impact and spectral characteristics of the musical signal.

Study of Attention Deficit and Hyperactivity Disorder Using the Method of Functional Tomography Based On Magnetic Encephalography Data

New method for the magnetic encephalography data analysis was proposed, making it possible to transform multichannel time series into the spatial structure of the human brain activity. In this paper we applied this method to the analysis of magnetic encephalograms, obtained from subjects with attention deficit and hyperactivity disorder. We have considered the experimental data, obtained with 275-channel magnetic encephalographs in McGill University and Montreal University. Magnetic encephalograms of the brain spontaneous activity were registered for 5 minutes in magnetically shielded room. Detailed multichannel spectra were obtained by the Fourier transform of the whole time series. For all spectral components, the inverse problem was solved in elementary current dipole model and the functional structure of the brain activity was calculated in the broad frequency band 0.3-50 Hz. It was found that frequency band relations are different in different experiments. We proposed to use these relations by the summary electric power produced by the sources in selected frequency band. The delta rhythm in frequency band 0.3 to 4 Hz was studied in detail. It was found, that many delta rhythm dipoles were localized outside the brain, and their spectrum consists of the heartbeat harmonics. It was concluded that in experiments considered, the delta rhythm represents the vascular activity of the head. To study the spatial distribution of all rhythms from theta to gamma the partial spectra of the brain divisions were calculated. The partial spectrum includes all frequencies produced by the dipole sources located in the region of brain selected at the magnetic resonance image. The method can be further applied to study encephalograms in various psychic disorders.

Brain Complex Network Characteristic Analysis of Fatigue during Simulated Driving Based on Electroencephalogram Signals

Fatigued driving is one of the major causes of traffic accidents. Frequent repetition of driving behavior for a long time may lead to driver fatigue, which is closely related to the central nervous system. In the present work, we designed a fatigue driving simulation experiment and collected the electroencephalogram (EEG) signals. Complex network theory was introduced to study the evolution of brain dynamics under different rhythms of EEG signals during several periods of the simulated driving. The results show that as the fatigue degree deepened, the functional connectivity and the clustering coefficients increased while the average shortest path length decreased for the delta rhythm. In addition, there was a significant increase of the degree centrality in partial channels on the right side of the brain for the delta rhythm. Therefore, it can be concluded that driving fatigue can cause brain complex network characteristics to change significantly for certain brain regions and certain rhythms. This exploration may provide a theoretical basis for further finding objective and effective indicators to evaluate the degree of driving fatigue and to help avoid fatigue driving.