Analysis of electrogenesis’ changes in mental retardation persons by using computer electroencephalography

Justification. Mental retardation is a persistent decrease in human cognitive activity against the background of organic damage to the central nervous system. Neurophysiological diagnostics, in particular electroencephalography (EEG), most adequately reflects the morpho-functional state of the central nervous system, which is the basis of the mechanisms of mental activity, and the originality of the bioelectrical activity of the brain can be considered as the main indicator that determines a decrease in the level of intellectual development and, thereby, characterizes this state. This provision actualizes the search for highly informative indicators of the originality of the bioelectrical activity of the brain in children with intellectual disabilities. Purspose. With the use of periodometric analysis investigate EEG’s indicators and interhemispheric asymmetry of rhythms amplitudes in MR patients. Materials and methods. The EEG was recorded in a state of calm wakefulness with closed eyes with Neuron-Spectrum-2 electroencephalograph. Differences in indicators were tracked using the calculation of the coefficient of compliance (CC), EEG functional asymmetry coefficients in amplitude were determined, too. Results. It was revealed that in MR patients the amplitudes of the rhythms were greater than in healthy subjects. The greatest increase was determined in theta rhythm in the anterior temporal and posterior temporal leads in the left hemispheres. Duration indices in the delta, theta and alpha ranges of the EEG in mental retardation compared with the control group were increased, and the indices of the duration of beta rhythms - decreased. When analyzing FMPA in MR persons it turned out that in right-handers the negativeness of FMPA indices increased, and in left-handers there was an increase in the positivity of FMPA indices. Conclusions 1. With mental retardation, the amplitudes of the rhythms were greater than in healthy people. The greatest increase was determined in theta rhythm in the anterior temporal and posterior temporal leads in the left hemispheres. 2. The indices of duration in the delta, theta and alpha ranges of the EEG of MR subjects were increased, and the indices of the duration of beta rhythms – decreased. 3. When analyzing FMPA in MR persons, it turned out that in right-handers the negativeness of FMPA indices increased, and in left-handers there was an increase in the positivity of FMPA indices.

Alpha and beta rhythms differentially support the effect of symbols on visual object recognition

Hearing spoken words can enhance visual object recognition, detection and discrimination. Yet, the mechanism underlying this facilitation is incompletely understood. On one account, words would not bias visual processes at early levels, but rather interact at later decision-making stages. More recent proposals posit that words can alter visual processes at early stages by activating category-specific priors in sensory regions. A prediction of this account is that top-down priors evoke changes in occipital areas before the presentation of visual stimuli. Here, we tested the hypothesis that neural oscillations can serve as a mechanism to activate language-mediated visual priors. Participants performed a cue-picture matching task where cues were either spoken words, in their native or second language, or natural sounds, while EEG and reaction times were recorded. Behaviorally, we replicated the previously reported label-advantage effect, with images cued by words being recognized faster than those cued by natural sounds. A time-frequency analysis of cue-target intervals revealed that this label-advantage was associated with enhanced power in posterior alpha (9-11 Hz) and beta oscillations (17-19 Hz), both of which were larger when the image was preceded by a word compared to a natural sound. Prestimulus alpha and beta rhythms were correlated with reaction time performance, yet they appeared to operate in different ways. Reaction times were faster when alpha power increased, but slowed down with enhancement of beta oscillations. These results suggest that alpha and beta rhythms work in tandem to support language-mediated visual object recognition, while showing an inverse relationship to behavioral performance.

STUDY OF THE ACTIVITY OF ALPHA AND BETA RHYTHMS ON EGG IN THE PROCESS OF MEMORIZATION WITH THE USAGE OF THE LOCI METHOD

Пространственная память в когнитивной психологии и нейробилогии понимается, как определенная часть памяти ответственная за накопление информации о местоположении [1, 2].Наше исследование направлено на изучение активности коры головного мозга с обычным запоминанием и с методом Loci среди студентов. Данная статья представляет изменение активности альфаритма коры в зависимости от метода запоминания. Spatial memory is a certain part of the mind that is responsible for the accumulation of data about the location ofcognitive psychology and neurobiology[1, 2]. The purpose of our research is to study the activity of the cerebral cortex with ordinary memory and with the Loci method among students. This article presents the modification in the alpha and beta rhythms activity of thecortex which depends on the method of memorization.

Flexible Frequency Switching in Adult Mouse Visual Cortex Is Mediated by Competition between Parvalbumin and Somatostatin Expressing Interneurons

Neuronal networks in rodent primary visual cortex (V1) can generate oscillations in different frequency bands depending on the network state and the level of visual stimulation. High-frequency gamma rhythms, for example, dominate the network's spontaneous activity in adult mice but are attenuated upon visual stimulation, during which the network switches to the beta band instead. The spontaneous local field potential (LFP) of juvenile mouse V1, however, mainly contains beta rhythms and presenting a stimulus does not elicit drastic changes in network oscillations. We study, in a spiking neuron network model, the mechanism in adult mice allowing for flexible switches between multiple frequency bands and contrast this to the network structure in juvenile mice that lack this flexibility. The model comprises excitatory pyramidal cells (PCs) and two types of interneurons: the parvalbumin-expressing (PV) and the somatostatinexpressing (SOM) interneuron. In accordance with experimental findings, the pyramidal-PV and pyramidal-SOM cell subnetworks are associated with gamma and beta oscillations, respectively. In our model, they are both generated via a pyramidal-interneuron gamma (PING) mechanism, wherein the PCs drive the oscillations. Furthermore, we demonstrate that large but not small visual stimulation activates SOM cells, which shift the frequency of resting-state gamma oscillations produced by the pyramidal-PV cell subnetwork so that beta rhythms emerge. Finally, we show that this behavior is obtained for only a subset of PV and SOM interneuron projection strengths, indicating that their influence on the PCs should be balanced so that they can compete for oscillatory control of the PCs. In sum, we propose a mechanism by which visual beta rhythms can emerge from spontaneous gamma oscillations in a network model of the mouse V1; for this mechanism to reproduce V1 dynamics in adult mice, balance between the effective strengths of PV and SOM cells is required.

Only the fastest corticospinal fibers contribute to beta corticomuscular coherence

ABSTRACTA common way to study human corticospinal transmission is with transcranial magnetic stimulation. However, this is biased to activity in the fastest conducting axons. It is unclear whether conclusions obtained in this context are representative of volitional activity in mild-to-moderate contractions. A possible alternative to overcome this limitation is to study the corticospinal transmission of endogenously generated brain activity. Here we study the transmission speeds of cortical beta rhythms travelling to the muscles during steady contractions. To do this, we introduce new methods to improve delay estimates in the corticomuscular transmission of beta rhythms, and which we validate both in simulations and experimentally. Applying these approaches to experimental data from humans, we show that corticomuscular beta transmission delays are only 1-2ms longer than expected from the fastest corticospinal pathway. Simulations using realistic distributions of the conduction velocities for descending axons projecting to lower motoneurons suggest two scenarios that can explain these results: either a very small fraction of only the fastest corticospinal axons selectively transmit beta activity, or else the entire pool does. The implications that these two scenarios have for our understanding of corticomuscular interactions are discussed in the final part of this manuscript.SIGNIFICANCEWe present and validate an improved methodology to measure the delay in the transmission of cortical beta activity to tonically active muscles. The estimated corticomuscular beta transmission delays which this yields are remarkably similar to those expected from transmission in the fastest corticospinal axons. A simulation of beta transmission along a pool of corticospinal axons using a realistic distribution of fiber diameters suggests two possible mechanisms by which fast corticomuscular transmission is achieved: either a very small fraction of descending axons transmits beta activity to the muscles or, alternatively, the entire population does and natural cancellation of slow channels occurs due to the distribution of axon diameters in the corticospinal tract.

The influence of wrist tapping based on the author’s methodology on the dynamics of intrahemispheric integration and ‘internal’ rhythm in healthy adults

The goal The goal is to study the lateralization of changes in intrahemispheric coherence in accordance with the basic rhythms of electroen- cephalography in healthy young people under the influence of tapping on the wrist in accordance with the author’s technique.Materials and methods: The conduct of this study was approved by the ethics com- mittee of KrasGMU. prof. V. F. Voyno-Yasenetsky (protocol No. 77/2017 of 06/26/2017). The study of the infl of wrist tapping according to the author’s technique on the coefficient of intrahemispheric coherence of the cerebral cortex in healthy volunteers (n2=63). Wrist tapping was carried out using the original technique (RF patent No. 2606489 of 01/10/2017). The analysis of intrahemispheric coherence in the pairs F3–T5, T5–O1, F3–O1, F4–T6, T6–O2, F4–O2 was carried out using a com- puter encephalographic complex (Neurocartograph, MBN Moscow).Results and discussions: According to the studies, it was shown that under the influence of tapping the hand according to the author’s technique, the state of sensory deprivation (closed eyes), statistically signifi changes in hemisphere coherence in theta and beta rhythms were not found, p>0.05, however, we showed a statistically significant (p<0.05) de- crease in hemisphere alpha-rhythm coherence in the right hemisphere in pairs F4–T4 (p=0.0000793) and F4–O2 (p=0.01711824), while the median coherence coeffi before and after tapping changed from 0.27 to 0.315 and from 0.13 to 0.175, respectively. At that time, we did not find statistically significant changes in the coherence of the hemisphere in similar pairs of the left hemisphere p>0.05. As a result of this study, when the wrist tapping was opened with the eyes of the subjects open, statistically significant changes in the coherence of the hemispheric alpha rhythm were detected only in the F3–O1 pair of the left hemisphere (p = 0.0000147), but not in the right hemisphere. At the same time, when the eyes of the volunteers were closed, there were no statistically significant changes in the coherence of the hemisphere in the theta and beta rhythms in both the left and right hemispheres.Conclusion. Thus, the use of tapping the wrist according to the author’s technique with the left hand in right-handed people in a state of sensory deprivation is promising for practical use in neurological practice, in particular in the management of patients with epilepsy and panic attacks, since a patient previously trained by the attending physician — neurorehabilitation, can use this the author’s program on his smartphone, in the case of an epileptic aura of focal epileptic seizures or precursors of panic attacks. However, the clinical application of the author’s technique needs detailed research.

Neural coordination mechanisms for associative memory recall and decision making in the hippocampal-prefrontal network

SUMMARYAssociative memory recall involves brain-wide networks comprising sensory and cognitive regions, with key roles for the hippocampus and prefrontal cortex (PFC). To investigate underlying network coordination mechanisms, we monitored activity in olfactory, hippocampal, and prefrontal regions in rats performing an associative memory task in which they recalled odor-place associations to obtain reward. During recall, the beta rhythm (15-30 Hz) was prominent and coherent across the three regions for correct decisions. Furthermore, single neurons and ensembles in both hippocampus and PFC encoded recalled associations. Ensemble dynamics predicted animals’ upcoming decisions and were linked specifically with beta rhythm coordination. Despite this relationship, we found that beta rhythms did not directly phase-modulate all association-coding neurons. Our findings suggest that beta rhythms coordinate ensemble activity within the hippocampal-prefrontal network to support associative memory recall and decision making, and play a permissive rather than instructive role in this process.HIGHLIGHTSBeta rhythms (15-30Hz) coordinate olfactory-hippocampal-prefrontal networksBeta coordination supports accurate odor-space associative memory recallSingle units and ensembles in CA1 and PFC encode associations and upcoming choicesBeta plays a permissive role in coordinating CA1-PFC ensemble activity underlying recall

Temporal codes of visual working memory in the human cerebral cortex

Visual working memory (vWM) is an important ability required for various cognitive tasks although its neural underpinnings remain controversial. While many studies have focused on theta (4-7 Hz) and gamma (> 30 Hz) rhythms as a substrate of vWM, here we show that temporal signals embedded in alpha (8-12 Hz) and beta (13-30 Hz) bands can be a good predictor of vWM capacity. Neural activity of healthy human participants was recorded with magnetoencephalography when they performed a classical vWM task (change detection). We analyzed changes in inter-peak intervals (IPIs) of oscillatory signals along with an increase in WM load (a number of to-be-memorized items, 1-6). Results showed a load-dependent reduction of IPIs in the parietal and frontal regions, indicating that alpha/beta rhythms became faster when multiple items were stored in vWM. Furthermore, this reduction in IPIs was positively correlated with individual vWM capacity, especially in the frontal cortex. Those results indicate that vWM is represented as a change in oscillation frequency in the human cerebral cortex.

Synchronization of Independent Neural Ensembles in Human EEG during Choice Tasks

During behavioral experiments, humans placed in a situation of having to choose between a more valuable but risky reward and a less valuable but guaranteed reward make their decisions in accordance with external situational factors and individual characteristics, such as inclination to risk or caution. In such situations, humans can be divided into “risk-inclined” and “risk-averse” (or “cautious”) subjects. In this work, characteristics of EEG rhythms, such as phase–phase relationships and time lags between rhythms, were studied in pairs of alpha–beta and theta–beta rhythms. Phase difference can also be expressed as a time lag. It has been suggested that statistically significant time lags between rhythms are due to the combined neural activity of anatomically separate, independent (in activation/inhibition processes) ensembles. The extents of synchronicity between rhythms were compared as percentages between risk-inclined and risk-averse subjects. The results showed that synchronicity in response to stimuli was more often observed in pairs of alpha–beta rhythms of risk-averse subjects compared with risk-inclined subjects during the choice of a more valuable but less probable reward. In addition, significant differences in the percentage ratio of alpha and beta rhythms were revealed between (i) cases of synchronization without long time lags and (ii) cases with long time lags between rhythms (from 0.08 to 0.1 s).