Effects of muscle shortening on single-fiber, motor unit, and compound muscle action potentials

Even under isometric conditions, muscle contractions are associated with some degree of fiber shortening. The effects of muscle shortening on extracellular electromyographic potentials have not been characterized in detail. Moreover, the anatomical, biophysical, and detection factors influencing the muscle-shortening effects have been neither identified nor understood completely. Herein, we investigated the effects of muscle shortening on the amplitude and duration characteristics of single-fiber, motor unit, and compound muscle action potentials. We found that, at the single-fiber level, two main factors influenced the muscle-shortening effects: (1) the electrode position and distance relative to the myotendinous zone and (2) the electrode distance to the maxima of the dipole field arising from the stationary dipole created at the fiber-tendon junction. Besides, at the motor unit and muscle level, two additional factors were involved: (3) the overlapping between the propagating component of some fibers with the non-propagating component of other fibers and (4) the spatial spreading of the fiber-tendon junctions. The muscle-shortening effects depend critically on the electrode longitudinal distance to the myotendinous zone. When the electrode was placed far from the myotendinous zone, muscle shortening resulted in an enlargement and narrowing of the final (negative) phase of the potential, and this enlargement became less pronounced as the electrode approached the fiber endings. For electrode locations close to the myotendinous zone, muscle shortening caused a depression of both the main (positive) and final (negative) phases of the potential. Beyond the myotendinous zone, muscle shortening led to a decrease of the final (positive) phase. The present results provide reference information that will help to identify changes in MUPs and M waves due to muscle shortening, and thus to differentiate these changes from those caused by muscle fatigue. Graphical abstract

A novel approach to design electrochemical aptamer-based biosensor for ultrasensitive detecting of zearalenone as a prevalent estrogenic mycotoxin

Background: Zearalenone is a well-known estrogenic mycotoxin produced by Fusarium species, a serious threat to the agricultural and food industries worldwide. Zearalenone, with its known metabolites, are biomarkers of exposure to certain fungi, primarily through food. It has considerable toxic effects on biological systems due to its carcinogenicity, mutagenicity, renal toxicity, teratogenicity, and immunotoxicity. Introduction: This study aims to design a simple, quick, precise, and cost-effective method on a biosensor platform to evaluate the low levels of this toxin in foodstuffs and agricultural products. Methods: An aptamer-based electrochemical biosensor was introduced that utilizes screen-printed gold electrodes instead of conventional electrodes. The electrode position process was employed to develop a gold nanoparticle-modified surface to enhance the electroactive surface area. Thiolated aptamers were immobilized on the surface of gold nanoparticles, and subsequently, the blocker and analyte were added to the modified surface. In the presence of a redox probe, electrochemical characterization of differential pulse voltammetry, cyclic voltammetry, and electrochemical impedance spectroscopy were used to investigate the various stages of aptasensor fabrication. Results: The proposed aptasensor for zearalenone concentration had a wide linear dynamic range covering the 0.5 pg/mL to 100 ng/mL with a 0.14 pg/mL detection limit. Moreover, this aptasensor had high specificity so that a non-specific analyte cannot negatively affect the selectivity of the aptasensor. Conclusion: Overall, due to its simple design, high sensitivity, and fast performance, this aptasensor showed a high potential for assessing zearalenone in real samples, providing a clear perspective for designing a portable and cost-effective device.

Anterior-Lateral Versus Anterior-Posterior Electrode Position for Cardioverting Atrial Fibrillation

Background: Smaller randomized studies have reported conflicting results regarding the optimal electrode position for cardioverting atrial fibrillation. However, anterior-posterior electrode position is widely used as a standard and believed to be superior to anterior-lateral electrode position. Therefore, we aimed to compare anterior-lateral and anterior-posterior electrode position for cardioverting atrial fibrillation in a multicenter randomized trial. Methods: In this multicenter, investigator-initiated, open-label trial, we randomly assigned patients with atrial fibrillation scheduled for elective cardioversion to anterior-lateral or anterior-posterior electrode position. The primary outcome was the proportion of patients in sinus rhythm after the first shock. The secondary outcome was the proportion of patients in sinus rhythm after up to four shocks escalating to maximum energy. Safety outcomes were any cases of arrhythmia during or after cardioversion, skin redness, and patient-reported peri-procedural pain. Results: We randomized 468 patients. The primary outcome occurred in 126 patients (54%) assigned to anterior-lateral electrode position and in 77 patients (33%) assigned to anterior-posterior electrode position, a risk difference of 22 percentage-points, 95%-confidence interval: 13-30, P<0.001. The number of patients in sinus rhythm after the final cardioversion shock was 216 patients (93%) assigned to anterior−lateral electrode position and 200 patients (85%) assigned to anterior-posterior electrode position, a risk difference of 7 percentage−points, 95%−confidence interval: 2−12. There were no significant differences between groups in any safety outcomes. Conclusions: Anterior-lateral electrode position was more effective than anterior-posterior electrode position for biphasic cardioversion of atrial fibrillation. There were no significant differences in any safety outcome.

Optimizing transcranial direct current stimulation (tDCS) electrode position, size, and distance doubles the on-target cortical electric field: Evidence from 3000 Human Connectome Project models

Transcranial direct current stimulation (tDCS) is a widely used noninvasive brain stimulation technique with mixed results and no FDA-approved therapeutic indication to date. So far, thousands of published tDCS studies have placed large scalp electrodes directly over the intended brain target and delivered the same stimulation intensity to each person. Inconsistent therapeutic results may be due to insufficient cortical activation in some individuals and the inability to determine an optimal dose. Here, we computed 3000 MRI-based electric field models in 200 Human Connectome Project (HCP) participants, finding that the largely unexamined variables of electrode position, size, and between-electrode distance significantly impact the delivered cortical electric field magnitude. At the same scalp stimulation intensity, smaller electrodes surrounding the neural target deliver more than double the on-target cortical electric field while stimulating only a fraction of the off-target brain regions. This new optimized tDCS method can ensure sufficient cortical activation in each person and could produce larger and more consistent behavioral effects in every prospective research and transdiagnostic clinical application of tDCS.

Nonhomogeneous volume conduction effects affecting needle electromyography: an analytical and simulation study

Objective: Needle electromyography (EMG) is used to study the electrical behavior of myofiber properties in patients with neuromuscular disorders. However, due to the complexity of electrical potential spatial propagation in nonhomogeneous diseased muscle, a comprehensive understanding of volume conduction effects remains elusive. Here, we develop a framework to study the conduction effect of extracellular abnormalities {and electrode positioning} on extracellular local field potential (LFP) recordings. Methods: The framework describes the macroscopic conduction of electrical potential in an isotropic, nonhomogeneous (i.e., two tissue) model. Numerical and finite element model simulations are provided to study the conduction effect in prototypical monopolar EMG measurements. Results: LFPs recorded are influenced in amplitude, phase and duration by the electrode position in regards to the vicinity of tissue with different electrical properties. Conclusion: The framework reveals the influence of multiple mechanisms affecting LFPs including changes in the distance between the source -- electrode and tissue electrical properties. Clinical significance: Our modeled predictions may lead to new ways for interpreting volume conduction effects on recorded EMG activity, for example in neuromuscular diseases that cause structural and compositional changes in muscle tissue. These change will manifest itself by changing the electric properties of the conductor media and will impact recorded potentials in the area of affected tissue.

Emotion recognition based on multi-channel EEG signals

Emotion recognition is a key technology of human-computer emotional interaction, which plays an important role in various fields and has attracted the attention of many researchers. However, the issue of interactivity and correlation between multi-channel EEG signals has not attracted much attention. For this reason, an EEG signal emotion recognition method based on 2DCNN-BiGRU and attention mechanism is tentatively proposed. This method firstly forms a two-dimensional matrix according to the electrode position, and then takes the pre-processed two-dimensional feature matrix as input, in the two-dimensional convolutional neural network (2DCNN) and the bidirectional gated recurrent unit (BiGRU) with the attention mechanism layer Extract spatial features and time domain features in, and finally classify by softmax function. The experimental results show that the average classification accuracy of this model are 93.66% and 94.32% in the valence and arousal, respectively.

Evaluation of cochlear implant electrode scalar position by 3 Tesla magnet resonance imaging

The estimation of scalar electrode position is a central point of quality control during the cochlear implant procedure. Ionic radiation is a disadvantage of commonly used radiologic estimation of electrode position. Recent developments in the field of cochlear implant magnets, implant receiver magnet position, and MRI sequence usage allow the postoperative evaluation of inner ear changes after cochlear implantation. The aim of the present study was to evaluate the position of lateral wall and modiolar cochlear implant electrodes using 3 T MRI scanning. In a prospective study, we evaluated 20 patients (10× Med-El Flex 28; 5× HFMS AB and 5× SlimJ AB) with a 3 T MRI and a T2 2D Drive MS sequence (voxel size: 0.3 × 0.3 × 0.9 mm) for the estimation of the intracochlear position of the cochlear implant electrode. In all cases, MRI allowed a determination of the electrode position in relation to the basilar membrane. This observation made the estimation of 19 scala tympani electrode positions and a single case of electrode translocation possible. 3 T MRI scanning allows the estimation of lateral wall and modiolar electrode intracochlear scalar positions.

Electrodeposition of Calcium Carbonate and Magnesium Carbonate from Hard Water on Stainless-Steel Electrode to Prevent Natural Scaling Phenomenon

This study focuses on preventing scale formation in hard waters by controlled electrode-position of Ca2+ and Mg2+ on a stainless-steel cathode at constant applied current intensity. The influence of the anode material, BDD or Ti/Pt/PbO2, cathode active area, stirring speed, and applied anodic current intensity on the inorganic carbon (IC), Ca2+, and Mg2+ removal was investigated. Assays were performed with model hard water solutions, simulating Bounouara (Algeria) water. The scaling inhibiting properties of the treated water were followed by measuring IC, calcium, and magnesium concentrations and chronoamperometric characterization of the treated solutions. The influence of the Ca/Mg molar ratio on the inorganic carbon removal by electrolysis was also evaluated, utilizing model solutions with different compositions. It was found that an increase in stirring speed or cathode geometric area favors IC and Ca2+ and Mg2+ removal rates. The applied current intensity was varied from 0.025 to 0.5 A, and the best results were obtained for 0.1 A, either in IC and Ca2+ and Mg2+ removals or by the accelerated scaling tests. However, energy costs increase with applied current. The deposit formed over the cathode does not seem to influence posterior deposition rate, and after eight consecutive assays, the solid deposition rate was kept constant. Ca/Mg ratio influences IC removal rate that increases with it. The results showed that hard-water scaling phenomena can be prevented by solid electrodeposition on the cathode at applied constant current.

Influence of electric field orientation on the effect of ocular current stimulation using full field electroretinogram

Ocular current stimulation (CS) exhibits potential for the treatment of neurodegenerative ocular diseases. For a full field electroretinogram (ffERG) we found no CS effect on the characteristic waves (a-wave, b’-wave, and b-wave). To investigate whether the orientation of the generated electric field has an influence on the CS effect, this study repeated the previous ffERG study with changing one CS electrode position and compared the results of both studies. In the first study 15 (8 m, 27.5 ± 4.5 years) and in the second study 17 (7 m, 22.0 ± 1.9 years) healthy volunteers were stimulated with an anodal, cathodal, and sham direct CS of 800 μA for 5 min in three sessions (randomized, different days). For both studies, a cut-sized ring rubber electrode was placed around the eye. A square rubber electrode was placed for the first study at the ipsilateral temple and for the second study at the visual cortex. Before (ERG 1) and during (ERG 2) the CS, the ffERG was measured. For both studies, the difference between the ERG 1 and ERG 2 measurement (CS effect) for the three characteristic waves was analyzed and compared between the studies. For statistical analysis, the Mann-Whitney U test with Bonferroni correction was applied (α = 0.05). The comparison of the data distribution showed only slight differences between the studies. The Mann-Whitney U test found no significant difference of the CS effect between the studies for all amplitudes and CS groups (p ≥ 0.0055). In the mean, the latency differences were smaller than the time resolution, therefore no statements for latency effects were possible. It can be concluded that the retinal cells generating the ffERG are not affected by ocular CS in either electrode montages tested.