Effect of Wrist Tapping on Interhemispheric Coherence in Patients with Juvenile Myoclonic Epilepsy

The aim of this study was to assess the dynamics of interhemispheric coherence (IC) as an indicator of integration of different areas of the brain and their participation in the performance of certain functions before and after wrist tapping (WT), using the author's method in juvenile myoclonic epilepsy (JME). Methods and Results: The study included 81 subjects of working age, including 51 clinically healthy volunteers (median age of 39[21;56] years) and 30 patients (median age of 27[23;38] years) with JME. Analysis of IC in the electrode pairs Fp1-Fp2, F3-F4, C3-C4, T3-T4 was performed using a computer encephalographic complex. A coherent EEG analysis was used to identify and evaluate the relationships between different areas of the brain. Based on the change in the coherence coefficients (CCs), the level of integrative activity of brain structures was quantified. In healthy volunteers, before and after WT, we observed a statistically significant decrease in CCs for the beta-1 band in the pairs Fp1-Fp2, F3-F4, and C3-C4 (P<0.05), while in the pair T3-T4, changes in CCs were not statistically significant (P>0.05). At the same time, a statistically significant decrease in CCs in the alpha band was found only in the frontal regions in the pairs Fp1-Fp2 and F3-F4 (P<0.05). No statistically significant changes were found in all the studied pairs in the theta band. When comparing CCs in JME patients in beta–1 and theta bands, before and after WT, we did not find statistically significant changes in CCs in all the studied electrode pairs. However, in the alpha band, we found a statistically significant decrease in CCs in the frontal region in the F3-F4 (P=0.0038) and C3-C4 electrode pairs (P=0.034). The results of the study of interhemispheric integration showed statistically significant differences between patients with JME and the control group. Conclusion: WT according to the author's method does not provoke the occurrence of interictal epileptiform discharges on the EEG and epileptic seizures in patients with JME. Coherent analysis showed positive changes in interhemispheric integrations of neurons in the beta–1 and alpha frequency ranges, mainly in the anterior hemispheres.

Reduced Interhemispheric Coherence in Cerebellar Kainic Acid-Induced Lateralized Dystonia

The execution of voluntary muscular activity is controlled by the primary motor cortex, together with the cerebellum and basal ganglia. The synchronization of neural activity in the intracortical network is crucial for the regulation of movements. In certain motor diseases, such as dystonia, this synchrony can be altered in any node of the cerebello-cortical network. Questions remain about how the cerebellum influences the motor cortex and interhemispheric communication. This research aims to study the interhemispheric cortical communication between the motor cortices during dystonia, a neurological movement syndrome consisting of sustained or repetitive involuntary muscle contractions. We pharmacologically induced lateralized dystonia to adult male albino mice by administering low doses of kainic acid on the left cerebellar hemisphere. Using electrocorticography and electromyography, we investigated the power spectral densities, cortico-muscular, and interhemispheric coherence between the right and left motor cortices, before and during dystonia, for five consecutive days. Mice displayed lateralized abnormal motor signs, a reduced general locomotor activity, and a high score of dystonia. The results showed a progressive interhemispheric coherence decrease in low-frequency bands (delta, theta, beta) during the first 3 days. The cortico-muscular coherence of the affected side had a significant increase in gamma bands on days 3 and 4. In conclusion, lateralized cerebellar dysfunction during dystonia was associated with a loss of connectivity in the motor cortices, suggesting a possible cortical compensation to the initial disturbances induced by cerebellar left hemisphere kainate activation by blocking the propagation of abnormal oscillations to the healthy hemisphere. However, the cerebellum is part of several overly complex circuits, therefore other mechanisms can still be involved in this phenomenon.

Reduced Interhemispheric Coherence after Cerebellar Vermis Output Perturbation

Motor coordination and motor learning are well-known roles of the cerebellum. Recent evidence also supports the contribution of the cerebellum to the oscillatory activity of brain networks involved in a wide range of disorders. Kainate, a potent analog of the excitatory neurotransmitter glutamate, can be used to induce dystonia, a neurological movement disorder syndrome consisting of sustained or repetitive involuntary muscle contractions, when applied on the surface of the cerebellum. This research aims to study the interhemispheric cortical communication between the primary motor cortices after repeated kainate application on cerebellar vermis for five consecutive days, in mice. We recorded left and right primary motor cortices electrocorticograms and neck muscle electromyograms, and quantified the motor behavior abnormalities. The results indicated a reduced coherence between left and right motor cortices in low-frequency bands. In addition, we observed a phenomenon of long-lasting adaptation with a modification of the baseline interhemispheric coherence. Our research provides evidence that the cerebellum can control the flow of information along the cerebello-thalamo-cortical neural pathways and can influence interhemispheric communication. This phenomenon could function as a compensatory mechanism for impaired regional networks.

Low-Frequency Oscillations Are a Biomarker of Injury and Recovery After Stroke

Background and Purpose— Low-frequency oscillations reflect brain injury but also contribute to normal behaviors. We examined hypotheses relating electroencephalography measures, including low-frequency oscillations, to injury and motor recovery poststroke. Methods— Patients with stroke completed structural neuroimaging, a resting-state electroencephalography recording and clinical testing. A subset admitted to an inpatient rehabilitation facility also underwent serial electroencephalography recordings. The relationship that electroencephalography measures (power and coherence with leads overlying ipsilesional primary motor cortex [iM1]) had with injury and motor status was assessed, focusing on delta (1–3 Hz) and high-beta (20–30 Hz) bands. Results— Across all patients (n=62), larger infarct volume was related to higher delta band power in bilateral hemispheres and to higher delta band coherence between iM1 and bilateral regions. In chronic stroke, higher delta power bilaterally correlated with better motor status. In subacute stroke, higher delta coherence between iM1 and bilateral areas correlated with poorer motor status. These coherence findings were confirmed in serial recordings from 18 patients in an inpatient rehabilitation facility. Here, interhemispheric coherence between leads overlying iM1 and contralesional M1 was elevated at inpatient rehabilitation facility admission compared with healthy controls (n=22), declining to control levels over time. Decreases in interhemispheric coherence between iM1 and contralesional M1 correlated with better motor recovery. Conclusions— Delta band coherence with iM1 related to greater injury and poorer motor status subacutely, while delta band power related to greater injury and better motor status chronically. Low-frequency oscillations reflect both injury and recovery after stroke and may be useful biomarkers in stroke recovery and rehabilitation.

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

The goal is to study the dynamics of the inter-hemispheric coherence coefficient of the cortex according to the main rhythms of the electroencephalogram before and after the BOS-therapy based on the wrist tapping on the author’s method and the effect of subclinical anxiety on the characteristics of wrist tapping in healthy adults.Materials and methods. The conduct of this study was approved by the ethical committee of KrasSMU. prof. V. F. Voyno-Yasenetsky (protocol No. 77/2017 dated June 26, 2017).The study was conducted in two stages. The first stage is the study of standards and the influence of wrist tapping according to the author’s method on the characteristic of the “internal” rhythm in healthy adults without anxiety and with subclinical anxiety (n1 = 60). The second stage is the study of the influence of wrist tapping according to the author’s method on the coefficient of hemispheric coherence in the frontal areas of the cerebral cortex in healthy volunteers (n2 = 63). Study of wrist tapping was carried out using the original technique (RF patent № 2606489 from 10.01.2017). Anxiety level testing was performed using a scale (HADS hospital anxiety and depression scale [1]). Analysis of interhemispheric coherence in Fp1 — Fp2, F3 — F4, T3 — T4 pairs was performed using a computer encephalographic complex (Neurokartograf, MBN Moscow).Results and discussions. The main characteristics of the “internal” rhythm according in healthy adults are statistically significant depending on the absence or presence of subclinical anxiety (1.13 Hz vs. 1.53 Hz, respectively). According to the author’s method, wrist tapping statistically significantly reduces the coefficient of interhemispheric coherence in Fp1-Fp2, F3-F4, C 3-C 4 pairs located above the convexital surface of the frontal cortex, which can be used as a method of non-pharmacological correction of anxiety disorders in the future.Conclusion. Subclinical anxiety affects the indicators of the “internal rhythm”, which is studied using wrist taping according to the author’s method. Wrist tapping in healthy adults leads to a decrease in the interhemispheric integration of frontal cortex neurons and interhemispheric coherence coefficients in beta1- (predominantly) and alpha rhythms, without affecting the coefficients of coherence in theta rhythm. Wrist tapping according to the author’s method is a promising option for BOS-therapy in adults to reduce the level of anxiety in normal and pathological conditions.

Language-Specific Synchronization of Neural Networks in the Human Brain

This study examines language-specific characteristics of the electric activity in bilinguals’ brains. The aim of this study was to evaluate language-specific characteristics of functional connectivity related to the perception of verbal information in different languages. Increasing synchronization of gamma band was detected in the association regions of left hemisphere during the Russian sonnets, alongside with interhemispheric coherence. The increase in synchronization exclusively in the left hemisphere was observed as in the case of English and Ukrainian sonnets. Increase of the coherence was shown in the left lateral and medial supplementary motor area when listening to Russian sonnets in comparison with Ukrainian. Decrease of coherence while listening to the Russian sonnets in comparison with Ukrainian was present in angular gyrus and superior parietal lobule. This evidence could indicate relatively lesser involvement of memory and attention when listening to Russian in comparison with the Ukrainian. Despite high proficiency of the participants, the mechanism of language perception could be different. Perhaps, an emotional response does not depend on the level of knowledge of the language but rather on its phonetic structure and prosody.

Role of Interhemispheric Cortical Interactions in Poststroke Motor Function

Background/Objective. We investigated interhemispheric interactions in stroke survivors by measuring transcranial magnetic stimulation (TMS)–evoked cortical coherence. We tested the effect of TMS on interhemispheric coherence during rest and active muscle contraction and compared coherence in stroke and older adults. We evaluated the relationships between interhemispheric coherence, paretic motor function, and the ipsilateral cortical silent period (iSP). Methods. Participants with (n = 19) and without (n = 14) chronic stroke either rested or maintained a contraction of the ipsilateral hand muscle during simultaneous recordings of evoked responses to TMS of the ipsilesional/nondominant (i/ndM1) and contralesional/dominant (c/dM1) primary motor cortex with EEG and in the hand muscle with EMG. We calculated pre- and post-TMS interhemispheric beta coherence (15-30 Hz) between motor areas in both conditions and the iSP duration during the active condition. Results. During active i/ndM1 TMS, interhemispheric coherence increased immediately following TMS in controls but not in stroke. Coherence during active cM1 TMS was greater than iM1 TMS in the stroke group. Coherence during active iM1 TMS was less in stroke participants and was negatively associated with measures of paretic arm motor function. Paretic iSP was longer compared with controls and negatively associated with clinical measures of manual dexterity. There was no relationship between coherence and. iSP for either group. No within- or between-group differences in coherence were observed at rest. Conclusions. TMS-evoked cortical coherence during hand muscle activation can index interhemispheric interactions associated with poststroke motor function and potentially offer new insights into neural mechanisms influencing functional recovery.

Modulating dream experience: Noninvasive brain stimulation over the sensorimotor cortex reduces dream movement

Recently, cortical correlates of specific dream contents have been reported, such as the activation of the sensorimotor cortex during dreamed hand clenching. Yet, the causal mechanisms underlying specific dream content remain largely elusive. Here, we investigated how alterations in the excitability of sensorimotor areas through transcranial direct current stimulation (tDCS) might alter dream content. Following bihemispheric tDCS or sham stimulation, participants who were awakened from REM sleep filled out a questionnaire on bodily sensations in dreams. tDCS, compared to sham stimulation, significantly decreased reports of dream movement, especially repetitive actions. Contrary to this, other types of bodily experiences, such as tactile or vestibular sensations, were not affected by tDCS, confirming the specificity of stimulation effects. In addition, tDCS reduced interhemispheric coherence in parietal areas and altered the phasic electromyography correlation between the two arms. These findings reveal that a complex reorganization of the motor network co-occurred with the reduction of dream movement, confirming spatial specificity of the stimulation site. We conclude that tDCS over the sensorimotor cortex causally interferes with dream movement during REM sleep.