Variations In Electrical Activity Research Articles

Explosive eruption style modulates volcanic electrification signals

Volcanic lightning detection has proven useful to volcano monitoring by providing information on eruption onset, source parameters, and ash cloud directions. However, little is known about the influence of changing eruptive styles on the generation of charge and electrical discharges inside the eruption column. The 2021 Tajogaite eruption (La Palma, Canary Islands) provided the rare opportunity to monitor variations in electrical activity continuously over several weeks using an electrostatic lightning detector. Here we show that throughout the eruption, silicate particle charging is the main electrification mechanism. Moreover, we find that the type of electrical activity is closely linked to the explosive eruption style. Fluctuations in the electrical discharge rates are likely controlled by variations in the mass eruption rate and/or changes in the eruption style. These findings hold promise for obtaining near real-time information on the dynamic evolution of explosive volcanic activity through electrostatic monitoring in the future.

Exaggerated High-Beta Oscillations are Associated with Cortical Thinning at the Motor Cortex in Parkinson's Disease.

Elevated β oscillations (13-35 Hz) are characteristic pathophysiology in Parkinson's Disease (PD). Cortical thinning has also been reported in the disease, however the relationship between these biomarkers of PD has not been established. By comparing electrophysiological measurements with cortical thickness, this study aims to reveal the pathoetiology of disease and symptoms in PD. Preoperative magnetic resonance imaging (MRI) and intraoperative local field potentials (LFPs) were collected from 34 subjects diagnosed with PD. Cortical surfaces were reconstructed from the images, and cortical thickness was extracted from the subregions where the recording electrode was placed in M1. LFPs were preprocessed and cleaned using a semiautomatic artifact detection algorithm, then power spectral densities (PSD) were computed and periodic and aperiodic frequency components were calculated. Nonparametric Spearman rank correlations assessed the relationship between electrophysiological components (i.e. center frequency (CF), power, bandwidth, 1/f exponent, knee), with cortical thickness. According to the CF of each subject's PSD, the cohort was split into two sub-groups: low-β peak (13-20 Hz) and high-β peak (20-35 Hz) groups. There was a significant negative correlation between power and cortical thickness only in the high-β subgroup (r=-0.48, p(corrected)=0.049). This relationship remained significant when correcting for age (r=-0.52,p=0.015), indicating that the effect of age on cortical thinning was not the determining factor. We did not find significant differences between UPDRS-III motor symptom scores for the low-and high-β subgroups. Of note is the dominance of high-β oscillatory power and its relationship with cortical thickness. As suggested by the literature, increased high-β activity during movement may be exaggerated in PD. These findings suggest that the characteristic cortical thinning in PD causes variation in electrical activity, leading to elevated high-β activity.Clinical relevance- This multimodal study provides additional insights on the pathophysiology and its relevance with morphology of Parkinson's Disease.

Chloride oscillation in pacemaker neurons regulates circadian rhythms through a chloride-sensing WNK kinase signaling cascade

Central pacemaker neurons regulate circadian rhythms and undergo diurnal variation in electrical activity in mammals and flies.1,2 Circadian variation in the intracellular chloride concentration of mammalian pacemaker neurons has been proposed to influence the response to GABAergic neurotransmission through GABAA receptor chloride channels.3 However, results have been contradictory,4-9 and a recent study demonstrated circadian variation in pacemaker neuron chloride without an effect on GABA response.10 Therefore, whether and how intracellular chloride regulates circadian rhythms remains controversial. Here, we demonstrate a signaling role for intracellular chloride in the Drosophila small ventral lateral (sLNv) pacemaker neurons. In control flies, intracellular chloride increases in sLNvs over the course of the morning. Chloride transport through sodium-potassium-2-chloride (NKCC) and potassium-chloride (KCC) cotransporters is a major determinant of intracellular chloride concentrations.11Drosophila melanogaster with loss-of-function mutations in the NKCC encoded by Ncc69 have abnormally low intracellular chloride 6h after lights on, loss of morning anticipation, and a prolonged circadian period. Loss of kcc, which is expected to increase intracellular chloride, suppresses the long-period phenotype of Ncc69 mutant flies. Activation of a chloride-inhibited kinase cascade, consisting of WNK (with no lysine [K]) kinase and its downstream substrate, Fray, is necessary and sufficient to prolong period length. Fray activation of an inwardly rectifying potassium channel, Irk1, is also required for the long-period phenotype. These results indicate that the NKCC-dependent rise in intracellular chloride in Drosophila sLNv pacemakers restrains WNK-Fray signaling and overactivation of an inwardly rectifying potassium channel to maintain normal circadian period length.

Compensatory ion transport buffers daily protein rhythms to regulate osmotic balance and cellular physiology

Between 6–20% of the cellular proteome is under circadian control and tunes mammalian cell function with daily environmental cycles. For cell viability, and to maintain volume within narrow limits, the daily variation in osmotic potential exerted by changes in the soluble proteome must be counterbalanced. The mechanisms and consequences of this osmotic compensation have not been investigated before. In cultured cells and in tissue we find that compensation involves electroneutral active transport of Na+, K+, and Cl− through differential activity of SLC12A family cotransporters. In cardiomyocytes ex vivo and in vivo, compensatory ion fluxes confer daily variation in electrical activity. Perturbation of soluble protein abundance has commensurate effects on ion composition and cellular function across the circadian cycle. Thus, circadian regulation of the proteome impacts ion homeostasis with substantial consequences for the physiology of electrically active cells such as cardiomyocytes.

Artificial intelligence methods for analysis of electrocardiogram signals for cardiac abnormalities: state-of-the-art and future challenges

Cardiovascular diseases (CVDs) in India and globally are the major cause of mortality, as revealed by the World Health Organization (WHO). The irregularities in the pace of heartbeats, called cardiac arrhythmias or heart arrhythmias, are one of the commonly diagnosed CVDs caused by ischemic heart disease, hypertension, alcohol intake, and stressful lifestyle. Other than the listed CVDs, the abnormality in the cardiac rhythm caused by the long term mental stress (stimulated by Autonomic Nervous System (ANS)) is a challenging issue for researchers. Early detection of cardiac arrhythmias through automatic electronic techniques is an important research field since the invention of electrocardiogram (ECG or EKG) and advanced machine learning algorithms. ECG (EKG) provides the record of variations in electrical activity associated with the cardiac cycle, used by cardiologists and researchers as a gold standard to study the heart function. The present work is aimed to provide an extensive survey of work done by researchers in the area of automated ECG analysis and classification of regular & irregular classes of heartbeats by conventional and modern artificial intelligence (AI) methods. The artificial intelligence (AI) based methods have emerged popularly during the last decade for the automatic and early diagnosis of clinical symptoms of arrhythmias. In this work, the literature is explored for the last two decades to review the performance of AI and other computer-based techniques to analyze the ECG signals for the prediction of cardiac (heart rhythm) disorders. The existing ECG feature extraction techniques and machine learning (ML) methods used for ECG signal analysis and classification are compared using the performance metrics like specificity, sensitivity, accuracy, positive predictivity value, etc. Some popular AI methods, which include, artificial neural networks (ANN), Fuzzy logic systems, and other machine learning algorithms (support vector machines (SVM), k-nearest neighbor (KNN), etc.) are considered in this review work for the applications of cardiac arrhythmia classification. The popular ECG databases available publicly to evaluate the classification accuracy of the classifier are also mentioned. The aim is to provide the reader, the prerequisites, the methods used in the last two decades, and the systematic approach, all at one place to further purse a research work in the area of cardiovascular abnormalities detection using the ECG signal. As a contribution to the current work, future challenges for real-time remote ECG acquisition and analysis using the emerging technologies like wireless body sensor network (WBSN) and the internet of things (IoT) are identified.

Variations in electrical activity of the heart as the pregnancy progresses

Background: Pregnancy is a physiological condition that brings a considerable alteration in hemodynamic activity of the maternal heart. It is very important to understand the cardiac functioning of maternal heart during normal pregnancy because apart from obstetric causes, cardiac disorders are the main cause of mortality in females .Study of electrical activity of the heart is a simple noninvasive and cost effective method which can also raise alarm about the pathological changes in the cardiac function. Aims & Objective: To study the intervals of Electrocardiogram (ECG) in pregnant women and to compare the same with healthy non pregnant women. Materials and Methods: A total of 223 females fulfilling the inclusion criteria were recruited for the study. They were divided into four groups - nonpregnant/control group (n=30), 1st trimester (n=36), 2nd trimester (n=64) and 3rd trimester (n= 93). ECG was recorded in lead II. Heart rate, PR, QT interval and QTc were also calculated. These parameters were compared between the groups using one way ANOVA test. A p value of less than 0.05 was considered as significant. Results: An increase in heart rate and QTc interval and decrease in PR interval was observed in pregnant women when compared with the heart rate of nonpregnant females. This was statistically insignificant when compared between controls and 1st trimester. However a significant change was observed between control group and 2nd/3rd trimester groups. This change was also observed significantly within the pregnant groups when compared with each other. Conclusion: The cardiovascular hemodynamic adaptation to pregnancy is a well-established physiological fact which was also apparent in this study. Further we noticed a significant change in electrical activity in pregnancy in terms of PR, QT and QTc intervals. These changes became more significant after 1st trimester and peaking during the 3rd trimester.

Optogenetic Probing of Fast Glutamatergic Transmission from Hypocretin/Orexin to Histamine NeuronsIn Situ

Hypothalamic hypocretin/orexin (hcrt/orx) neurons coordinate sleep-wake cycles, reward seeking, and body energy balance. Neurochemical data suggest that hcrt/orx cells contain several transmitters, but what hcrt/orx cells release onto their projection targets is unknown. A major pathway by which hcrt/orx neurons are thought to promote arousal is through projections to tuberomammillary histamine (HA) neurons. To study the impact of the electrical activity in hcrt/orx cells on HA neurons, we genetically targeted the light-activated excitatory ion channel channelrhodopsin-2 (ChR2) to the plasma membrane of hcrt/orx cells, and performed patch-clamp recordings from HA cells in acute mouse brain slices. Stimulation of ChR2-containing fibers with millisecond flashes of blue light produced fast postsynaptic currents in HA neurons, with a high connection probability (≈60% of HA cells were connected to ≈40% of hcrt/orx cells expressing ChR2). These inputs depended on tetrodotoxin-sensitive action potentials, had kinetics typical of glutamatergic responses mediated by AMPA receptors, were blocked by the AMPA receptor blocker CNQX, and displayed multiple forms of short-term plasticity (depression in ≈70% trials, facilitation in ≈30% trials, both often in the same cell). Furthermore, stimulation of hcrt/orx axons at physiological frequencies rapidly and reversibly increased action potential firing in HA cells, an effect that was abolished by blockade of AMPA receptors. These results provide the first functional evidence that hcrt/orx neurons are capable of fast glutamatergic control of their projection targets, and suggest that variations in electrical activity of hcrt/orx axons can induce rapid changes in long-range signals generated by HA neurons.

Characterization of Traps in Crystalline Silicon on Glass Film Using Deep-Level Transient Spectroscopy

Thin crystalline silicon films on glass substrate, fabricated using solid phase crystallization for application in thin-film solar cells, were investigated by deep level transient spectroscopy (DLTS). The analyses of the DLTS spectra obtained during temperature scans revealed presence of carrier traps related to dislocations in silicon. Other carrier traps of yet unknown nature were detected as well. Variations of electrical activity of the traps were achieved applying variations in the process of the film formation. These changes were also detected during DLTS measurements, suggesting a possibility for applying of DLTS for the investigation and characterization of the thin-film Si material on glass.

Lightning activity variations over three islands in a tropical monsoon region

Seasonal, intra-annual and inter-annual variations in electrical activity over three islands (Carnicobar, Little Andaman and North Andaman) of different areas but located in similar synoptic conditions in the south Bay of Bengal are examined from the Tropical Rainfall Measuring Mission (TRMM) satellite observations. The 10-year monthly means of flash density and flash rate mostly increase with the increase in the area of island even on a monthly time scale. Differences in orography/latitudes of the islands with the same area, however, may produce a scatter in this flash density/rate–island area relationship. Present results are, however, not sufficient to resolve between the thermal and aerosol hypotheses for the role of islands in enhancing the lightning activity. However, these can be understood from the interaction of convective activity over the islands with the large-scale monsoon airflow in the region. Annual means of flash density and flash rate do not show any significant change over a period of 10years. Furthermore, the conclusions of theoretical studies that the strengthening of updraft causes the increase in flash rate in a storm, are upheld in the present analysis.

Effects of Mesenteric Ischemia and Reperfusion on Small Bowel Electrical Activity

Previous studies involving basic electrical rhythm (BER) have not been carried out far enough to fully characterize the relationship between mesenteric ischemia and BER. The phenomenon of reperfusion injury has also not been correlated with BER activity. The goal of this study was to characterize changes in BER during mesenteric ischemia and reperfusion and to correlate them with changes in pathology.Methods.Serosal electrodes were used to record the electrical activity of rabbit jejunum (n= 20) at baseline, during ischemia (90–210 min), and during reperfusion (120–240 min). BER frequency and amplitude were monitored, and biopsies were taken at the end of ischemia and reperfusion. A pathologist blinded to the specimen identity graded the histology on a scale of 0 (no changes) to 6 (transmural necrosis). Pairedttest, the Kruskal–Wallis test of nonparametric ranks, and Fisher'srtoztest were used for statistical significance where appropriate.Results.BER frequency and amplitude fell significantly after 15 min of ischemia and became undetectable by 90 min of ischemia in all animals. The likelihood that BER would return during reperfusion was highly correlated with length of ischemia (r= 0.99). Longer periods of reperfusion were associated with increasing pathologic grade.Conclusions.BER frequency and amplitude are very sensitive to ischemia and their changes occur well before histopathologic changes. The variation in electrical activity of the small bowel during ischemia and reperfusion is a dynamic process that reflects the metabolic state of the smooth muscle. If electrical activity of the bowel is to be used for assessment of viability, continuous recordings more accurately reflect the metabolic state of the smooth muscle.

Plasticity in GABAAReceptor Subunit mRNA Expression by Hypothalamic Magnocellular Neurons in the Adult Rat

The magnocellular hypothalamic neurons exhibit a substantial degree of structural and functional plasticity over the time of pregnancy, parturition, and lactation. This study has used in situ hybridization techniques to examine whether the content of alpha 1, alpha 2, beta 2, gamma 2 GABAA receptor subunit mRNAs expressed by these cells fluctuates over this period. A process of regional, followed by cellular and then topographical, analyses within the supraoptic (SON) and posterior paraventricular (PVN) nuclei revealed that an increase in magnocellular alpha 1 subunit mRNA content occurred during the course of pregnancy up to day 19, after which a decline in expression was detected on the day of parturition. Significant fluctuations of this nature were observed only in the oxytocin neuron-enriched regions of the SON and PVN. The expression of alpha 2, beta 2, and gamma 2 subunit mRNAs in the SON and PVN and of all subunit mRNAs in the cingulate cortex did not change over this period. During lactation, gamma 2 subunit mRNA content within the PVN increased significantly on day 14 of lactation as compared with day 7, and topographical analysis suggested that it involved principally magnocellular vasopressin neurons. These results demonstrate the cell-and subunit-specific regulation of GABAA receptor mRNA expression within the hypothalamic magnocellular system. In particular, they suggest that fluctuations in alpha 1 subunit expression may contribute to the marked variations in electrical activity exhibited by magnocellular oxytocin neurons at the time of parturition. More generally, they provide evidence in support of GABAA receptor plasticity within a physiological context in the adult rat brain.

Stebic Revisited

AbstractWe re-examine the technique of Scanning Transmission Electron Beam Induced Conductivity and report on the acquisition of remote contact EBIC images at 200keV showing variations in electrical activity within P-doped CdTe.

Testing and estimation for variable single evoked brain potentials

The task of validly quantifying variations in electrical activity recorded when the brain is processing external or internal events is addressed. Three new statistical tests sensitive to different types of response changes, which test the null hypothesis that there is a homogeneous signal, are presented. In the case of latency jitter, the testing procedure was developed together with a procedure for estimating the unknown signal shifts. The tests provide a statistically valid and powerful tool in investigating signal variation, even with strong colored noise. Moreover, the differential sensitivity to different types of variations allows a study of the underlying signal variability even though the single signal cannot be estimated.

Circadian rhythms of serotonin and the electrical activity of the frontal ganglion of the cockroach,Periplaneta americana

Rhythmic circadian variations in the spontaneous electrical activity of the frontal ganglion (FG) of the cockroach,Periplaneta americana, have been shown, and the neurotransmitter (NT) involved in this activity has been identified as serotonin (5-hydroxytryptamine, 5-HT). During the 24-h day, the diurnal variations in the electrical activity and the levels of 5-HT and its immediate metabolite 5-hydroxyindole acetic acid (5-HIAA) were maximal at 24.00 h and minimal at 12.00 h.