Non-invasive Electrophysiology Research Articles

The Russian Society of Holter Monitoring and Noninvasive Electrophysiology (ROHME) and the International Holter Society: a quarter century of cooperation

The Russian Society of Holter Monitoring and Noninvasive Electrophysiology (ROHME) and the International Holter Society: a quarter century of cooperation

The beginning of Russian Holter Monitoring and Non-invasive Electrophysiology Society (ROHMINE) (memoirs)

The beginning of Russian Holter Monitoring and Non-invasive Electrophysiology Society (ROHMINE) (memoirs)

Early detection of dark-affected plant mechanical responses using enhanced electrical signals

BackgroundMechanical damage to plants triggers local and systemic electrical signals that are eventually decoded into plant defense responses. These responses are constantly affected by other environmental stimuli in nature, for instance, light fluctuation. In recent years, studies on decoding plant electrical signals powered by various machine learning models are increasing in a sense of early prediction or detection of different environmental stresses that threaten plant growth or crop yields. However, the main bottleneck is the low-throughput nature of plant electrical signals, making it challenging to obtain a substantial amount of training data. Consequently, training these models with small datasets often leads to unsatisfactory performance.ResultsIn the present work, we set out to decode wound-induced electrical signals (also termed slow wave potentials, SWPs) from plants that are deprived of light to different extents. Using non-invasive electrophysiology, we separately collected sets of local and distal SWPs from the treated plants. Then, we proposed a workflow based on few-shot learning to automatically identify SWPs. This workflow incorporates data preprocessing, feature extraction, data augmentation and classifier training. We established the integral and the first-order derivative as features for efficiently classifying SWPs. We then proposed an Adversarial Autoencoder (AAE) structure to augment the SWP samples. Combining them, the Random Forest classifier allowed remarkable classification accuracies of 0.99 for both local and systemic SWPs. In addition, in comparison to two other reported methods, our proposed AAE structure enabled better classification results using our tested features and classifiers.ConclusionsThe results of this study establish new features for efficiently classifying wound-induced electrical signals, which allow for distinguishing dark-affected local and systemic plant wound responses. We also propose a new data augmentation structure to generate virtual plant electrical signals. The methods proposed in this study could be further applied to build models for crop plants using electrical signals as inputs, and also to process other small-scale signals.

Intracranial electroencephalography reveals effector-independent evidence accumulation dynamics in multiple human brain regions.

Neural representations of perceptual decision formation that are abstracted from specific motor requirements have previously been identified in humans using non-invasive electrophysiology; however, it is currently unclear where these originate in the brain. Here we capitalized on the high spatiotemporal precision of intracranial EEG to localize such abstract decision signals. Participants undergoing invasive electrophysiological monitoring for epilepsy were asked to judge the direction of random-dot stimuli and respond either with a speeded button press (N = 24), or vocally, after a randomized delay (N = 12). We found a widely distributed motor-independent network of regions where high-frequency activity exhibited key characteristics consistent with evidence accumulation, including a gradual buildup that was modulated by the strength of the sensory evidence, and an amplitude that predicted participants' choice accuracy and response time. Our findings offer a new view on the brain networks governing human decision-making.

Resting 12-lead electrocardiography for adults and children. 2023 Guidelines

Russian Society of Cardiology (RSC)Developed with the special contribution of the Russian Functional Diagnostics Association, Russian Holter Monitoring and Non-invasive Electrophysiology Society, Russian Pediatric Cardiology Association.

Overcoming harmonic hurdles: Genuine beta-band rhythms vs. contributions of alpha-band waveform shape

Abstract Beta-band activity in the human cortex as recorded with noninvasive electrophysiology is of diverse origin. In addition to genuine beta-rhythms, there are numerous nonsinusoidal alpha-band rhythms present in the human brain, which will result in harmonic beta-band peaks. This type of activity has different temporal and response dynamics than genuine beta-rhythms. Here, it is argued that in the analysis of higher-frequency rhythms, the relationship to lower-frequency rhythms needs to be clarified. Only in that way we can arrive at strong, methodologically valid interpretations of potential functional roles and generative mechanisms of neural oscillations.

Neural entrainment underpins sensorimotor synchronization to dynamic rhythmic stimuli

Neural entrainment, defined as unidirectional synchronization of neural oscillations to an external rhythmic stimulus, is a topic of major interest in the field of neuroscience. Despite broad scientific consensus on its existence, on its pivotal role in sensory and motor processes, and on its fundamental definition, empirical research struggles in quantifying it with non-invasive electrophysiology. To this date, broadly adopted state-of-the-art methods still fail to capture the dynamic underlying the phenomenon.Here, we present event-related frequency adjustment (ERFA) as a methodological framework to induce and to measure neural entrainment in human participants, optimized for multivariate EEG datasets. By applying dynamic phase and tempo perturbations to isochronous auditory metronomes during a finger-tapping task, we analyzed adaptive changes in instantaneous frequency of entrained oscillatory components during error correction. Spatial filter design allowed us to untangle, from the multivariate EEG signal, perceptual and sensorimotor oscillatory components attuned to the stimulation frequency.Both components dynamically adjusted their frequency in response to perturbations, tracking the stimulus dynamics by slowing down and speeding up the oscillation over time. Source separation revealed that sensorimotor processing enhanced the entrained response, supporting the notion that the active engagement of the motor system plays a critical role in processing rhythmic stimuli. In the case of phase shift, motor engagement was a necessary condition to observe any response, whereas sustained tempo changes induced frequency adjustment even in the perceptual oscillatory component. Although the magnitude of the perturbations was controlled across positive and negative direction, we observed a general bias in the frequency adjustments towards positive changes, which points at the effect of intrinsic dynamics constraining neural entrainment.We conclude that our findings provide compelling evidence for neural entrainment as mechanism underlying overt sensorimotor synchronization, and highlight that our methodology offers a paradigm and a measure for quantifying its oscillatory dynamics by means of non-invasive electrophysiology, rigorously informed by the fundamental definition of entrainment.

Continuous contractile force and electrical signal recordings of 3D cardiac tissue utilizing conductive hydrogel pillars on a chip.

Heart-on-chip emerged as a potential tool for cardiac tissue engineering, recapitulating key physiological cues in cardiac pathophysiology. Controlled electrical stimulation and the ability to provide directly analyzed functional readouts are essential to evaluate the physiology of cardiac tissues in the heart-on-chip platforms. In this scenario, a novel heart-on-chip platform integrating two soft conductive hydrogel pillar electrodes was presented here. Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) and cardiac fibroblasts were seeded into the apparatus to create 3D human cardiac tissues. The application of electrical stimulation improved functional performance by altering the dynamics of tissue structure and contractile development. The contractile forces that cardiac tissues contract was accurately measured through optical tracking of hydrogel pillar displacement. Furthermore, the conductive properties of hydrogel pillars allowed direct and non-invasive electrophysiology studies, enabling continuous monitoring of signal changes in real-time while dynamically administering drugs to the cardiac tissues, as shown by a chronotropic reaction to isoprenaline and verapamil. Overall, the platform for acquiring contractile force and electrophysiological signals in situ allowed monitoring the tissue development trend without interrupting the culture process and could have diverse applications in preclinical drug testing, disease modeling, and therapeutic discovery.

Studying memory processes at different levels with simultaneous depth and surface EEG recordings.

Investigating cognitive brain functions using non-invasive electrophysiology can be challenging due to the particularities of the task-related EEG activity, the depth of the activated brain areas, and the extent of the networks involved. Stereoelectroencephalographic (SEEG) investigations in patients with drug-resistant epilepsy offer an extraordinary opportunity to validate information derived from non-invasive recordings at macro-scales. The SEEG approach can provide brain activity with high spatial specificity during tasks that target specific cognitive processes (e.g., memory). Full validation is possible only when performing simultaneous scalp SEEG recordings, which allows recording signals in the exact same brain state. This is the approach we have taken in 12 subjects performing a visual memory task that requires the recognition of previously viewed objects. The intracranial signals on 965 contact pairs have been compared to 391 simultaneously recorded scalp signals at a regional and whole-brain level, using multivariate pattern analysis. The results show that the task conditions are best captured by intracranial sensors, despite the limited spatial coverage of SEEG electrodes, compared to the whole-brain non-invasive recordings. Applying beamformer source reconstruction or independent component analysis does not result in an improvement of the multivariate task decoding performance using surface sensor data. By analyzing a joint scalp and SEEG dataset, we investigated whether the two types of signals carry complementary information that might improve the machine-learning classifier performance. This joint analysis revealed that the results are driven by the modality exhibiting best individual performance, namely SEEG.

A mesh microelectrode array for non-invasive electrophysiology within neural organoids

Organoids are emerging in vitro models of human physiology. Neural models require the evaluation of functional activity of single cells and networks, which is commonly measured by microelectrode arrays. The characteristics of organoids clash with existing in vitro or in vivo microelectrode arrays. With inspiration from implantable mesh electronics and growth of organoids on polymer scaffolds, we fabricated suspended hammock-like mesh microelectrode arrays for neural organoids. We have demonstrated the growth of organoids enveloping these meshes and the culture of organoids on meshes for up to one year. Furthermore, we present proof-of-principle recordings of spontaneous electrical activity across the volume of an organoid. Our concept enables a new class of microelectrode arrays for in vitro models of three-dimensional electrically active tissue.

Electrophysiological activity from over the cerebellum and cerebrum during eye blink conditioning in human subjects.

We report the results of an experiment in which electrophysiological activity was recorded from the human cerebellum and cerebrum in a sample of 14 healthy subjects before, during and after a classical eye blink conditioning procedure with an auditory tone as conditional stimulus and a maxillary nerve unconditional stimulus. The primary aim was to show changes in the cerebellum and cerebrum correlated with behavioral ocular responses. Electrodes recorded EMG and EOG at peri-ocular sites, EEG from over the frontal eye-fields and the electrocerebellogram (ECeG) from over the posterior fossa. Of the 14 subjects half strongly conditioned while the other half were resistant. We confirmed that conditionability was linked under our conditions to the personality dimension of extraversion-introversion. Inhibition of cerebellar activity was shown prior to the conditioned response, as predicted by Albus (1971). However, pausing in high frequency ECeG and the appearance of a contingent negative variation (CNV) in both central leads occurred in all subjects. These led us to conclude that while conditioned cerebellar pausing may be necessary, it is not sufficient alone to produce overt behavioral conditioning, implying the existence of another central mechanism. The outcomes of this experiment indicate the potential value of the noninvasive electrophysiology of the cerebellum.

ACA pumps maintain leaf excitability during herbivore onslaught

Recurrent damage by lepidopteran folivores triggers repeated leaf-to-leaf electrical signaling. We found that the ability to propagate electrical signals-called slow wave potentials-was unexpectedly robust and was maintained in plants that had experienced severe damage. We sought genes that maintain tissue excitability during group insect attack. When Arabidopsis thaliana P-Type II Ca2+-ATPase mutants were mechanically wounded, all mutants tested displayed leaf-to-leaf electrical signals. However, when the auto-inhibited Ca2+-ATPase double-mutant aca10 aca12 was attacked by Spodoptera littoralis caterpillars, electrical signaling failed catastrophically, and the insects consumed these plants rapidly. The attacked double mutant displayed petiole base deformation and chlorosis, which spread acropetally into laminas and led to senescence. A phloem-feeding aphid recapitulated these effects, implicating the vasculature in electrical signaling failure. Consistent with this, ACA10 expressed in phloem companion cells in an aca10 aca12 background rescued electrical signaling and defense during protracted S.littoralis attack. When expressed in xylem contact cells, ACA10 partially rescued these phenotypes. Extending our analyses, we found that prolonged darkness also caused wound-response electrical signaling failure in aca10 aca12 mutants. Our results lead to a model in which the plant vasculature acts as a capacitor that discharges temporarily when leaves are subjected to energy-depleting stresses. Under these conditions, ACA10 and ACA12 function allows the restoration of vein cell membrane potentials. In the absence of these gene functions, vascular cell excitability can no longer be restored efficiently. Additionally, this work demonstrates that non-invasive electrophysiology is a powerful tool for probing early events underlying senescence.

Spatial and Temporal Distribution of Information Processing in the Human Dorsal Anterior Cingulate Cortex.

The dorsal anterior cingulate cortex (dACC) is a key node in the human salience network. It has been ascribed motor, pain-processing and affective functions. However, the dynamics of information flow in this complex region and how it responds to inputs remain unclear and are difficult to study using non-invasive electrophysiology. The area is targeted by neurosurgery to treat neuropathic pain. During deep brain stimulation surgery, we recorded local field potentials from this region in humans during a decision-making task requiring motor output. We investigated the spatial and temporal distribution of information flow within the dACC. We demonstrate the existence of a distributed network within the anterior cingulate cortex where discrete nodes demonstrate directed communication following inputs. We show that this network anticipates and responds to the valence of feedback to actions. We further show that these network dynamics adapt following learning. Our results provide evidence for the integration of learning and the response to feedback in a key cognitive region.

Noninvasive Electrophysiology: Emerging Prospects in Aquatic Neurotoxicity Testing.

The significance of neurotoxicological risks associated with anthropogenic pollution is gaining increasing recognition worldwide. In this regard, perturbations in behavioral traits upon exposure to environmentally relevant concentrations of neurotoxic and neuro-modulating contaminants have been linked to diminished ecological fitness of many aquatic species. Despite an increasing interest in behavioral testing in aquatic ecotoxicology there is, however, a notable gap in understanding of the neurophysiological foundations responsible for the altered behavioral phenotypes. One of the canonical approaches to explain the mechanisms of neuro-behavioral changes is functional analysis of neuronal transmission. In aquatic animals it requires, however, invasive, complex, and time-consuming electrophysiology techniques. In this perspective, we highlight emerging prospects of noninvasive, in situ electrophysiology based on multielectrode arrays (MEAs). This technology has only recently been pioneered for the detection and analysis of transient electrical signals in the central nervous system of small model organisms such as zebrafish. The analysis resembles electroencephalography (EEG) applications and provides an appealing strategy for mechanistic explorative studies as well as routine neurotoxicity risk assessment. We outline the prospective future applications and existing challenges of this emerging analytical strategy that is poised to bring new vistas for aquatic ecotoxicology such as greater mechanistic understanding of eco-neurotoxicity and thus more robust risk assessment protocols.

Excitation and Contraction of the Failing Human Heart In Situ and Effects of Cardiac Resynchronization Therapy: Application of Electrocardiographic Imaging and Speckle Tracking Echo-Cardiography

Despite the success of cardiac resynchronization therapy (CRT) for treating heart failure (HF), the rate of nonresponders remains 30%. Improvements to CRT require understanding of reverse remodeling and the relationship between electrical and mechanical measures of synchrony. The objective was to utilize electrocardiographic imaging (ECGI, a method for noninvasive cardiac electrophysiology mapping) and speckle tracking echocardiography (STE) to study the physiology of HF and reverse remodeling induced by CRT. We imaged 30 patients (63% male, mean age 63.7 years) longitudinally using ECGI and STE. We quantified CRT-induced remodeling of electromechanical parameters and evaluated a novel index, the electromechanical delay (EMD, the delay from activation to peak contraction). We also measured dyssynchrony using ECGI and STE and compared their effectiveness for predicting response to CRT. EMD values were elevated in HF patients compared to controls. However, the EMD values were dependent on the activation sequence (CRT-paced vs. un-paced), indicating that the EMD is not intrinsic to the local tissue, but is influenced by factors such as opposing wall contractions. After 6 months of CRT, patients had increased contraction in native rhythm compared to baseline pre-CRT (baseline: −8.55%, 6 months: −10.14%, p = 0.008). They also had prolonged repolarization at the location of the LV pacing lead. The pre-CRT delay between mean lateral LV and RV electrical activation time was the best predictor of beneficial reduction in LV end systolic volume by CRT (Spearman’s Rho: −0.722, p < 0.001); it outperformed mechanical indices and 12-lead ECG criteria. HF patients have abnormal EMD. The EMD depends upon the activation sequence and is not predictive of response to CRT. ECGI-measured LV activation delay is an effective index for CRT patient selection. CRT causes persistent improvements in contractile function.

Current status of pediatric electrophysiology in Latin America: a LAHRS survey

Over the last years, pediatric electrophysiology (EP) has evolved as a consolidated subspecialty of pediatric cardiology. In the USA, Canada, and Europe, there is a clear picture of the status of pediatric EP, but the situation in Latin America is largely unknown. A descriptive cross-sectional observational study was performed. A survey was conducted by the Latin American Heart Rhythm Society in Spanish and Portuguese to assess the status of development of pediatric EP across Latin American countries. There are physicians practicing pediatric EP in 11 Latin American countries. The scope of the practices includes clinical and non-invasive EP as well as performing invasive EP procedures. All the current pediatric EP interventions are performed in most of Latin American countries. Pediatric electrophysiology is present as a subspecialty in half of the countries in Latin America, and all the current electrophysiology procedures and therapeutic technologies are available in most Latin American countries.

Dynamic relationships between spontaneous and evoked electrophysiological activity

Spontaneous neural activity fluctuations have been shown to influence trial-by-trial variation in perceptual, cognitive, and behavioral outcomes. However, the complex electrophysiological mechanisms by which these fluctuations shape stimulus-evoked neural activity remain largely to be explored. Employing a large-scale magnetoencephalographic dataset and an electroencephalographic replication dataset, we investigate the relationship between spontaneous and evoked neural activity across a range of electrophysiological variables. We observe that for high-frequency activity, high pre-stimulus amplitudes lead to greater evoked desynchronization, while for low frequencies, high pre-stimulus amplitudes induce larger degrees of event-related synchronization. We further decompose electrophysiological power into oscillatory and scale-free components, demonstrating different patterns of spontaneous-evoked correlation for each component. Finally, we find correlations between spontaneous and evoked time-domain electrophysiological signals. Overall, we demonstrate that the dynamics of multiple electrophysiological variables exhibit distinct relationships between their spontaneous and evoked activity, a result which carries implications for experimental design and analysis in non-invasive electrophysiology.

Source analyses of axial and vestibular evoked potentials associated with brainstem-spinal reflexes show cerebellar and cortical contributions

In this work we examine the possible neural basis for two brainstem-spinal reflexes using source analyses of brain activity recorded over the cortex and posterior fossa. In a sample of 5 healthy adult subjects, using axial and vestibular stimulation by means of applied impulsive forces, evoked potentials were recorded with 63 channels using a 10 % cerebellar extension montage. In parallel, EMG was recorded from soleus and tibialis anterior muscles and accelerometry from the lower leg. Recordings over the cerebellum (ECeG) confirmed the presence of short latency (SL) potentials and these were associated with changes in high-frequency power. The SL responses to the two stimulus modalities differed in that the axial stimulation produced an initial pause and then a burst in the high-frequency ECeG, followed by excitation/inhibition in soleus while vestibular stimulation produced an initial burst then a pause, followed by inhibition/excitation in soleus. These short latency responses were followed by longer latency N1/P2/N2 responses in the averaged EEG, which were maximal at FCz. Brain Electrical Source Analysis (BESA) demonstrated both cerebellar and cerebral cortical contributions to the short-latency responses and primarily frontal cortex contributions to the long-latency EPs. The latency and polarity of the SL EPs, in conjunction with changes in high-frequency spontaneous activity, are consistent with cerebellar involvement in the control of brainstem-spinal reflexes. The early involvement of frontal cortex and subsequent later activity may be an indicator of the activation of the cortical motor-related system for rapid responses which may follow the reflexive components. These findings provide evidence of the feasibility of non-invasive electrophysiology of the human cerebellum and have demonstrated cerebellar and frontal activations associated with postural-related stimuli.

A Morphable Ionic Electrode Based on Thermogel for Non-Invasive Hairy Plant Electrophysiology.

Plant electrophysiology lays the foundation for smart plant interrogation and intervention. However, plant trichomes with hair-like morphologies present topographical features that challenge stable and high-fidelity non-invasive electrophysiology, due to the inadequate dynamic shape adaptability of conventional electrodes. Here, this issue is overcome using a morphable ionic electrode based on a thermogel, which gradually transforms from a viscous liquid to a viscoelastic gel. This transformation enables the morphable electrode to lock into the abrupt hairy surface irregularities and establish a conformal and adhesive interface. It achieves down to one tenth of the impedance and 4-5 times the adhesive strengths of conventional hydrogel electrodes on hairy leaves. As a result of the improved electrical and mechanical robustness, the morphable electrode can record more than one order of magnitude higher signal-to-noise ratio on hairy plants and maintains high-fidelity recording despite plant movements, achieving superior performance to conventional hydrogel electrodes. The reported morphable electrode is a promising tool for hairy plant electrophysiology and may be applied to diversely textured plants for advanced sensing and modulation.

Recommendations from the Association for European Paediatric and Congenital Cardiology for training in diagnostic and interventional electrophysiology.

The field of electrophysiology (EP) in paediatric cardiology patients and adults with congenital heart disease is complex and rapidly growing. The current recommendations for diagnostic and invasive electrophysiology of the working group for Cardiac Dysrhythmias and Electrophysiology of the Association for European Paediatric and Congenital Cardiology acknowledges the diveristy of European countries and centers. These training recommendations can be fulfilled in a manageable period of time, without compromising the quality of training required to become an expert in the field of paediatric and congenital EP and are for trainees undergoing or having completed accredited paediatric cardiologist fellowship. Three levels of expertise, the training for General paediatric cardiology EP, for non-invasive EP and invasive EP have been defined. This Association for European EP curriculum describes the theoretical and practicsal knowledge in clinical EP; catheter ablation, cardiac implantable electronic devices, inherited arrhythmias and arrhythmias in adults with congenital heart defects for the 3 levels of expertise.