Bioelectric Signals Research Articles

Robot-assisted training using hybrid assistive limb ameliorates gait ability in patients with amyotrophic lateral sclerosis

ObjectiveThe Hybrid Assistive Limb (HAL; CYBERDYNE, Inc., Japan) is a wearable robot device that provides effective gait assistance according to voluntary intention by detecting weak bioelectrical signals of neuromuscular activity on the surface of the skin. We used HAL for patients with amyotrophic lateral sclerosis (ALS) to determine whether HAL training had an effect on their gait ability. MethodsWe conducted a single-center, single-arm, observational study. Patients with ALS underwent HAL training once per day (20–40 min per session) for 9–10 days for at least 4 weeks. Gait ability was evaluated using the 2-minute walk test, the 10-meter walk test without the assistance of HAL, and activities of daily living (ADL) using the Barthel Index and Functional Independence Measures before and after a full course of HAL training. ResultsThere were no dropouts or adverse events during the observation period. Gait function improved after HAL training. The 2-minute walk test revealed a mean gait distance of 73.87 m (36.65) at baseline and 89.9m (36.70) after HAL training (p = 0.004). The 10-meter walk test showed significantly improved cadence, although gait speed, step length on the 10-m walk, or ADL measurements did not change significantly. ConclusionsAlthough HAL is not a curative treatment for ALS, our data suggest that HAL may be effective in ameliorating and preserving gait ability in patients with ALS.

Water-resistant and underwater adhesive ion-conducting gel for motion-robust bioelectric monitoring

• The adding of bioionic liquid improves conductivity and underwater adhesion of gels. • The gel electrode exhibits low impedance at physiologically relevant frequencies. • The noise of the gel electrode is much lower than the commercial gel electrodes. • The gel electrode effectively reduces the influence of motion artifacts. • It obtains real-time high-quality bioelectric signals in the underwater environment. Bio-adhesive and ion-conductive hydrogels are of great significance in the field of bioelectric monitoring, but many challenges remain for practical applications in complex conditions and underwater environments. Here, we report a bioelectrical electrode based on ion-conductive gel with excellent water-resistant, underwater adhesion, and swelling resistance for application in the aquatic environment. Especially, the gel electrode exhibits extremely low impedance (<10 Ω) at physiologically relevant frequencies, long-term electrical and structural stability in the aqueous environment. The static noise (19 uV) and dynamic noise (30 uV) it generating are much lower than the current bioelectrodes and commercial gel electrodes. It can effectively reduce the influence of motion artifacts and obtain real-time high-quality electrocardiogram and electromyography signals underwater. Therefore, it shows great potential in long-term motion-robust underwater bioelectric monitoring.

Endogenous Electric‐Field‐Coupled Electrospun Short Fiber via Collecting Wound Exudation (Adv. Mater. 9/2022)

Tissue Repair In article number 2108325, Wenguo Cui and co-workers report the fabrication of a 3D bionic short fiber scaffold with excellent reversible hydroscopicity and biostable conductivity. This scaffold helps to achieve precise tissue remodeling by collecting a large amount of secretions in the early stages of wound healing and transmitting bioelectrical signals to proactively match the cascade reaction of tissue repair.

Robust Tattoo Electrode Prepared by Paper-Assisted Water Transfer Printing for Wearable Health Monitoring

Long-term and stable monitoring of bioelectrical signals represented by electrocardiogram (ECG) has a great application value for wearable electronics. The ECG monitoring require low-cost, flexible and robust electrical system that can work throughout daily activities. In this article, we propose a paper-assisted strategy to fabricate a tattoo ECG electrode based on the low-cost water transfer printing technology. Similar to the tattoo attached on the skin, the fabricated electrode allows complying with the skin deformation comfortably and accommodating the local strains. The ECG signals collected by the tattoo electrode have a high signal to noise ratio, robustness, mechanical stability and strong immunity to motion artifact even under the severe deformation of skin. The tattoo electrode enables convenient and long-period ECG monitoring during various activities, including exercising, sweating, rubbing, and flushing. As a proof-of-concept, a soft wireless ECG system is developed by integrating with the tattoo electrode, commercialized IC chips, and a low-energy Bluetooth module to achieve the functions of signal acquisition, data processing and communication. The measured results show that the proposed strategy has a promising application for wearable health monitoring system.

Early Postoperative Rehabilitation Using the Hybrid Assistive Limb (HAL) Lumbar Type in Patients With Hip Fracture: A Pilot Study.

Objective: To extend life expectancy after surgery, patients with hip fractures need to improve their mobility quickly through postoperative rehabilitation. Voluntary hip joint motion supported by the hybrid assistive limb (HAL) lumbar type, an exoskeleton robot suit characterized by its ability to detect the wearer’s intentions through the bioelectrical signals and assist hip extension motions at an optimal timing, may be effective to improve mobility in patients with hip joint dysfunction after surgery. We aimed to introduce rehabilitation using the HAL lumbar type in the early period after hip fracture surgery.Methods: Patients who underwent internal fixation for hip fracture at a single institution were prospectively enrolled. They received early postoperative rehabilitation (forward and backward bending of the lumbar spine, pelvic tilt forward and backward, standing up, and squatting) using the HAL lumbar type (six times a week for 15 min per session). Five-times-sit-to-stand (FTSS) and timed-up-and-go (TUG) tests were conducted at baseline before HAL rehabilitation (pre-HAL) and after the HAL rehabilitation (post-HAL) intervention.Results: We enrolled 14 patients (one man, 13 women) in this study. There were no adverse events, and all patients were able to complete the entire rehabilitation program. Post-HAL FTSS showed significant improvement compared with pre-HAL and had a large effect size of 1.81 (95% CI = 0.93 to 2.66) and sufficient power.Conclusions: Robotic rehabilitation with HAL lumbar type could be introduced without adverse events, even in the early postoperative period following surgery for hip fracture. Further study is needed to develop an appropriate rehabilitation protocol using the HAL lumbar type.

Mechanisms Underlying Influence of Bioelectricity in Development.

To execute the intricate process of development, cells coordinate across tissues and organs to determine where each cell divides and differentiates. This coordination requires complex communication between cells. Growing evidence suggests that bioelectrical signals controlled via ion channels contribute to cell communication during development. Ion channels collectively regulate the transmembrane potential of cells, and their function plays a conserved role in the development of organisms from flies to humans. Spontaneous calcium oscillations can be found in nearly every cell type and tissue, and disruption of these oscillations leads to defects in development. However, the mechanism by which bioelectricity regulates development is still unclear. Ion channels play essential roles in the processes of cell death, proliferation, migration, and in each of the major canonical developmental signaling pathways. Previous reviews focus on evidence for one potential mechanism by which bioelectricity affects morphogenesis, but there is evidence that supports multiple different mechanisms which are not mutually exclusive. Evidence supports bioelectricity contributing to development through multiple different mechanisms. Here, we review evidence for the importance of bioelectricity in morphogenesis and provide a comprehensive review of the evidence for several potential mechanisms by which ion channels may act in developmental processes.

Neural stem cell-laden 3D bioprinting of polyphenol-doped electroconductive hydrogel scaffolds for enhanced neuronal differentiation

The development of three-dimensional (3D) bioprinting technology opens a door for constructing bionic nerve tissue scaffolds on demand for nerve injury repair. However, the electrical insulation of the current nerve tissue scaffolds fabricated by 3D bioprinting hinders the bioelectrical signal transmission between cells, limiting the therapeutic effect in nerve tissue repair. To address this issue, we have developed a neural stem cell (NSC)-laden 3D bioprinted electroconductive hydrogel (ECH) scaffold, composed of modified poly(3,4-ethylenedioxythiophene) (PEDOT), gelatin methacrylate/polyethylene glycol diacrylate hydrogel matrix, and NSCs, to promote the electron propagation in the scaffold for enhanced nerve regeneration. In our strategy, PEDOT is modified by doping with chondroitin sulfate and tannic acid (TA) to improve its water-solubility and electric property. With moderate mechanical strength and good electroconductivity, the 3D ECH scaffold provides a benign conductive microenvironment for the adhesion, growth, and proliferation of the encapsulated NSCs. Clearly, in the 3D ECH scaffolds, the NSCs not only maintain high cell viability (>90%) after bioprinting, but also tend to differentiate into neurons with extended neurites. This study testifies for the first time the effect of polyphenol structure belonging to TA on neuronal differentiation of NSCs, and offers a new insight into designing electroconductive biomaterials to induce neuronal regeneration for nerve injury repair and neurodegenerative disease therapy.

Fructus Xanthii-Inspired Low Dynamic Noise Dry Bioelectrodes for Surface Monitoring of ECG.

The microstructured surfaces of bioelectrical dry electrodes are important aspects of dry electrode design. However, traditional surfaces for microstructured bioelectrical dry electrodes are costly to produce and require complex fabrication methods. In this study, a novel stacked-template method is proposed for the first time, rapidly producing microstructured dry electrodes at a low cost and with a large surface area. Three types of microstructured Ag/AgCl thermoplastic polyurethane (TPU) electrodes with a Fructus xanthii-inspired barb structure (FXbs) are prepared using this method; then, the dynamic friction, hair interference resistance, electrochemical, and electrocardiogram (ECG) signal acquisition performance of the electrodes are tested, and the dynamic noise characteristics of the electrodes are comprehensively evaluated with simulated instruments. Compared to the plate structure, the dynamic friction coefficient of the FXbs electrode improved by about 38.8%, exhibiting strong hair interference resistance. In addition, the FXbs electrode exhibits low dynamic noise and comparable performance to the wet electrode, in terms of signal acquisition, when it is tested using simulated instruments. Therefore, the prepared FXbs electrode increases the friction coefficient between the electrode and the skin, which effectively resolves issues related to dynamic noise in bioelectrical signals, making it suitable for dynamic measurements.

Endogenous Electric-Field-Coupled Electrospun Short Fiber via Collecting Wound Exudation.

Endogenous electric fields (EF) are the basis of bioelectric signal conduction and the priority signal for damaged tissue regeneration. Tissue exudation directly affects the characteristics of endogenous EF. However, current biomaterials lead to passive repair of defect tissue due to limited management of early wound exudates and inability to actively respond to coupled endogenous EF. Herein, the 3D bionic short-fiber scaffold with the functions of early biofluid collection, response to coupled endogenous EF, is constructed by guiding the short fibers into a 3D network structure and subsequent multifunctional modification. The scaffold exhibits rapid reversible water absorption, reaching maximum after only 30 s. The stable and uniform distribution of polydopamine-reduced graphene oxide endows the scaffold with stable electrical and mechanical performances even after long-term immersion. Due to its unique - bionic structure and tissue affinity, the scaffold further acts as an "electronic skin," which transmits endogenous bioelectricity via absorbing wound exudates, promoting the treatment of diabetic wounds. Furthermore, under the endogenous EF, the cascade release of vascular endothelial growth factor accelerates the healing process. Thus, the versatile scaffold is expected to be an ideal candidate for repairing different defect tissues, especially electrosensitive tissues.

Analysis of Bioelectrical Impedance Spectrum for Elbow Stiffness Based on Hilbert-Huang Transform.

With the advent of posttraumatic elbow rehabilitation, prevention of elbow stiffness has become a key part of the development of sports medicine. In order to clarify the time point of joint movement after internal fixation to the elbow and to provide a mechanical model for individualized diagnosis. This paper uses electromagnetic wave detection technology to quickly detect the bioelectrical impedance signal of the patient's lesion location, then passes the message to the upper control system for processing, summarizes the improved Hilbert–Huang transform to deep learning, and deep learning algorithms and computer technology are used to mine the bioelectrical impedance signal of the elbow joint. The simulation and human experiment results show that bioelectrical impedance signals can clarify the pathogenesis of elbow joint stiffness and the relationship between rehabilitation treatment time and duration. It has the advantages of low cost, high fitting accuracy, strong robustness, and noninvasiveness.

Acousto-optic wavelet processing of bioelectric signals

Wavelet analysis is one of the most efficient methods of the informative signals characteristics investigation. First shown the possibility of informative signals wavelet processing by means of the acousto-optic processor with time integration. The possibility of the realization of both power spectrum calculation and performance of wavelet transform of bioelectric signals in the real time mode has been proved. The analysis is listed which describes its operation in different modes. Keywords: wavelet analysis, bioelectric signals, acousto-optic processors, time integration

Opportunities for agent based modeling of retinal stem cell transplantation.

Opportunities for agent based modeling of retinal stem cell transplantation.

Scoping Review of Bioelectrical Signals Uses in Videogames for Evaluation Purposes

Bioelectric signals can improve assessment in videogames by helping to better understand user experience, evaluate attention, or study the cognitive and physical effects of games. Use of signals is therefore relevant to better evaluate and understand the impact and effects of videogames on players, and specially so in the field of serious games, such as educational or training games, to gain insights into the learning processes; or in games for health to better evaluate non-conscious effects on the player’s body. We examine how biological signals (bioelectric + eye-tracking) are being used and collected in the field of video games, including the choice of signals, the devices used to collect them (e.g., wearables), the purposes for which they are collected, and the results reported from their use. As a result of this systematic literature review, 81 articles have been analyzed, finding that electrocardiograms and encephalograms are the most frequently used signals. The main use of these bioelectrical signals is to evaluate player engagement, level of difficulty, and stress during the gameplay. But there are also examples where signals are used to detect health problems, or as evidence to compare educational games with other learning activities. This review informs researchers interested in better understanding the benefits and limitations of biological signals for video games, providing an overview of studies conducted in recent years and the associated devices described in those studies. Limitations in this field include signal noise issues as well as the amount of time required to calibrate the devices during experiments, adding to the complexity of user testing. It is necessary to work on tools that facilitate experiments with large groups of users in parallel as well as to work on open software and low-cost devices that allow the emergence of a greater number of studies in this field, given for example their potential in the field of educational games to better understand the learning processes of users.

Research on Fatigue Classification of Flight Simulation Training

Abstract Fatigue is an important factor affecting modern flight safety. It can easily lead to a decline in the pilot's operational capabilities, misjudgments and flight illusions. Moreover, it may even cause serious flight accidents. In this paper, a wearable wireless physiological device is used to obtain pilot electrocardiogram data in simulated flight experiments. Bioelectric signals have higher reliability than image information, and are not easily affected by the external environment (such as shooting angle and light intensity). On the other hand, neural networks have been widely used in various classification and regression tasks. In this study, the EEG was collected in the driving flight simulator, and after simple filtering and preprocessing, the time domain data was sent directly to the convolutional neural network, eliminating the need for additional feature extraction operations. We found that the convolutional neural network can effectively amplify the fluctuation details of the time domain data and train the pilot fatigue state recognition model. The results show that the recognition accuracy of the convolutional neural network model reaches 98%, which is 26% and 12% higher than the traditional k-nearest neighbor classification algorithm (KNN) and support vector machine (SVM) model, respectively. The recognition model based on convolutional neural network established in this paper is suitable for the recognition of pilot fatigue status. This has important practical significance for reducing flight accidents caused by pilot fatigue, and provides a theoretical basis for pilot fatigue risk management and the development of intelligent aircraft autopilot systems.

Heterogeneous Integration of Thin-Film Organic and Inorganic Devices for Optical Based Bioelectrical and Chemical Sensing

Directly visualizing electrical and chemical signals via optical approaches is an effective and powerful method for analyzing biological activities in a remote and high-throughput manner. Here we develop a heterogeneously integrated optoelectronic sensor that optically monitors the changes of bioelectrical and biochemical signals. Fabricated via epitaxial liftoff and transfer printing, the thin-film, microscale sensor combines a photodiode and a light-emitting diode (LED) made of inorganic III–V compound semiconductor heterostructures, as well as an organic electrochemical transistor (OECT). Ascribed to the matching condition among the heterogeneously integrated components, luminescent emissions of the sensor, which can be captured with a fluorescence microscope, dynamically respond to input electrical signals and are systematically characterized. Through voltage dependent luminance variations, the device optically records synthesized electrocardiography (ECG) signals with peak amplitudes from 100 mV to 10 mV. Furthermore, the integrated sensor is capable of selectively detecting calcium variations when immersing into the aqueous solution. The integrated sensor combines the advantages of inorganic and organic semiconductors and offers opportunities to wirelessly detect biological activities at a large scale.

Conversion of bioelectric sEMG signals into analog form for the BLDC motors control

This paper presents the process of converting the bioelectrical sEMG signal into an analog signal, which is useful from the point of view of motor or actuator control. The constructed measurement path for signal acquisition enables examining the "raw" signal from sEMG sensors and tracing the entire path of signal processing up to its "useful" form, i.e., the analog signal reflecting the degree of contraction of a selected muscle. This paper presents the successive signal processing and filtering stages and discusses the electrical circuits used in the signal acquisition process.

Intermuscular coupling network analysis of upper limbs based on R-vine copula transfer entropy.

In the field of neuroscience, it is very important to evaluate the causal coupling characteristics between bioelectrical signals accurately and effectively. Transfer entropy is commonly used to analyze complex data, especially the causal relationship between data with non-linear, multidimensional characteristics. However, traditional transfer entropy needs to estimate the probability density function of the variable, which is computationally complex and unstable. In this paper, a new and effective method for entropy transfer is proposed, by means of applying R-vine copula function estimation. The effectiveness of R-vine copula transfer entropy is first verified on several simulations, and then applied to intermuscular coupling analysis to explore the characteristics of the intermuscular coupling network of muscles in non-fatigue and fatigue conditions. The experiment results show that as the muscle group enters the fatigue state, the community structure can be adjusted and the muscle nodes participating in the exercise are fully activated, enabling the two-way interaction between different communities. Finally, it comes to the conclusion that the proposed method can make accurate inferences about complex causal coupling. Moreover, the characteristics of the intermuscular coupling network in both non-fatigue and fatigue states can provide a new theoretical perspective for the diagnosis of neuromuscular fatigue and sports rehabilitation, which has good application value.

Wearable microfluidic-based e-skin sweat sensors.

Electronic skins (e-skins) are soft (deformable and stretchable) state-of-the-art wearable devices that emulate the attributes of human skin and act as a Human–Machine Interface (HMI). Recent advances in e-skin for real-time detection of medical signals such as pulse, temperature, electromyogram (EMG), electroencephalogram (EEG), electrooculogram (EOG), electrocardiogram (ECG), and other bioelectric signals laid down an intelligent foundation for early prediction and diagnosis of diseases with a motive of reducing the risk of the ailment reaching to the end stage. In particular, sweat testing has been employed in diverse applications ranging from medical diagnosis of diabetes, cystic fibrosis, tuberculosis, blood pressure, and autonomic neuropathy to evaluating fluid and electrolyte balance in athletes. Typically, sweat testing techniques are done by trained experts and require off-body measurements, which prevent individuals from de-coding health issues quickly and independently. With the onset of soft electronics, wearable sweat sensors overcome this disadvantage via in situ sweat measurements with real-time feedback, timely diagnosis, creating the potential for preventive care and treatment. Over the past few decades, wearable microfluidic-based e-skin sweat sensors have paved a new way, promising sensing interfaces that are highly compatible with arranging medical and electronic applications. The present review highlights the recent research carried out in the microfluidic-based wearable sweat sensors with a critical focus on real-time sensing of lactate, chloride, and glucose concentration; sweat rate, simultaneously with pH, and total sweat loss for preventive care, timely diagnosis, and point-of-care health and fitness monitoring.

Vagus nerve spiking activity modulates prefrontal–amygdalar circuit related to anxiety

The vagus nerve has critical for brain-body interaction. It conveys internal physiological information from peripheral organs to the brain, causing interoception. Although numerous studies have shown that an alternation in vagal sensory input affects emotional states such as anxiety and depression, the mechanism by which vagus nerve activity is correlated with anxiety-related brain activity remains unknown. We have previously established a vagal spike recording method using a cuff-shaped electrode while simultaneously recording central and peripheral bioelectrical signals in freely moving rodents. In the present study, we investigated correlation between vagus nerve and anxiety-related brain activity on an elevated plus maze. We combined the recording method of vagus nerve with recording of local field potentials (LFPs) of the prefrontal cortex and the amygdala, which are crucial for expression of anxiety. Vagus nerve activity was negatively correlated with anxiety-related 4-7 Hz activity in the prefrontal cortex and the amygdala. The correlation was abolished by left cervical vagotomy. Chronic social defeat stress decorrelated vagus nerve activity with 4-7 Hz LFP oscillations. These results imply neurophysiological mechanisms underlying anxiolytic effects of vagus nerve stimulation and provide insights into neurophysiological underpinnings of the relationship between vagus nerve and emotion-related behavior.

A multifunctional ATP-generating system by reduced graphene oxide-based scaffold repairs neuronal injury by improving mitochondrial function and restoring bioelectricity conduction.

Peripheral nerve injury usually impairs neurological functions. The excessive oxidative stress and disrupted bioelectrical conduction gives rise to a hostile microenvironment and impedes nerve regeneration. Therefore, it is of urgent need to develop tissue engineering products which help alleviate the oxidative insults and restore bioelectrical signals. Melatonin (MLT) is an important endogenous hormone that diminishes the accumulation of reactive oxygen species. Reduced graphene oxide (RGO) possesses the excellent electrical conductivity and biocompatibility. In this study, a multilayered MLT/RGO/Polycaprolactone (PCL) composite scaffold was fabricated with beaded nanostructures to improve cell attachment and proliferation. It also exhibited stable mechanical properties by high elastic modulus and guaranteed structural integrity for nerve regeneration. The live/dead cell staining and cell counting kit assay were performed to evaluate the toxicity of the scaffold. JC-1 staining was carried out to assess the mitochondrial potential. The composite scaffold provided a biocompatible interface for cell viability and improved ATP production for energy supply. The scaffold improved the sensory and locomotor function recovery by walking track analysis and electrophysiological evaluation, reduced Schwann cell apoptosis and increased its proliferation. It further stimulated myelination and axonal outgrowth by enhancing S100β, myelin basic protein, β3-tubulin, and GAP43 levels. The findings demonstrated functional and morphological recovery by this biomimetic scaffold and indicated its potential for translational application.