Machine learning classifiers for electrode selection in the design of closed-loop neuromodulation devices for episodic memory improvement.

Successful neuromodulation approaches to alter episodic memory require closed-loop stimulation predicated on the effective classification of brain states. The practical implementation of such strategies requires prior decisions regarding electrode implantation locations. Using a data-driven approach, we employ support vector machine (SVM) classifiers to identify high-yield brain targets on a large data set of 75 human intracranial electroencephalogram subjects performing the free recall (FR) task. Further, we address whether the conserved brain regions provide effective classification in an alternate (associative) memory paradigm along with FR, as well as testing unsupervised classification methods that may be a useful adjunct to clinical device implementation. Finally, we use random forest models to classify functional brain states, differentiating encoding versus retrieval versus non-memory behavior such as rest and mathematical processing. We then test how regions that exhibit good classification for the likelihood of recall success in the SVM models overlap with regions that differentiate functional brain states in the random forest models. Finally, we lay out how these data may be used in the design of neuromodulation devices.

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 positioning is widely used as a standard and believed to be superior to anterior-lateral electrode positioning. Therefore, we aimed to compare anterior-lateral and anterior-posterior electrode positioning 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 either anterior-lateral or anterior-posterior electrode positioning. 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 4 shocks escalating to maximum energy. Safety outcomes were any cases of arrhythmia during or after cardioversion, skin redness, and patient-reported periprocedural pain. RESULTS: We randomized 468 patients. The primary outcome occurred in 126 patients (54%) assigned to the anterior-lateral electrode position and in 77 patients (33%) assigned to the anterior-posterior electrode position (risk difference, 22 percentage points [95% CI, 13-30]; P<0.001). The number of patients in sinus rhythm after the final cardioversion shock was 216 (93%) assigned to anterior-lateral electrode positioning and 200 (85%) assigned to anterior-posterior electrode positioning (risk difference, 7 percentage points [95% CI, 2-12]). There were no significant differences between groups in any safety outcomes. CONCLUSIONS: Anterior-lateral electrode positioning was more effective than anterior-posterior electrode positioning for biphasic cardioversion of atrial fibrillation. There were no significant differences in any safety outcome. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03817372.

Perylene diimide/MXene-modified graphitic pencil electrode-based electrochemical sensor for dopamine detection.

The synthesis of novel architecture comprising perylene diimide (PDI)-MXene (Ti3C2TX)-integrated graphitic pencil electrode for electrochemical detection of dopamine (DA) is reported. The good electron passage between PDI-MXene resulted in an unprecedented nano-adduct bearing enhanced electrocatalytic activity with low-energy electronic transitions. The anionic groups of PDI corroborated enhanced active surface area for selective binding and robust oxidation of DA, thereby decreasing the applied potential. Meanwhile, the MXene layers acted as functional conducive support for PDI absorption via strong H-bonding. The considerable conductivity of MXene enhanced electron transportation thus increasing the sensitivity of sensing interface. The inclusively engineered nano-adduct resulted in robust DA oxidation with ultra-sensitivity (38.1 µAµM-1cm-2), and low detection limit (240 nM) at very low oxidation potential (-0.135 V). Moreover, it selectively signaled DA in the presence of physiological interferents with wide linearity (100-1000 µM). The developed transducing interface performed well in human serum samples with RSD (0.1 to 0.4%) and recovery (98.6 to 100.2%) corroborating the viability of the practical implementation of this integrated system. Graphical abstract Schematic illustration of the oxidative process involved on constructed sensing interface for the development of a non-enzymatic dopamine sensor.

Detecting slender objects with uncertainty based on keypoint-displacement representation.

Slender objects are long and thin objects. Existing object detection networks are not specially designed for detecting slender objects. We propose a method to detect slender objects. We represent slender objects with a keypoint-displacement pattern instead of using axis-aligned bounding boxes, avoiding problems like orientation confusion and wrong elimination. In our network, three parallel branches predict keypoint heatmaps, displacement vector field, and displacement uncertainty heatmap respectively. We add the uncertainty branch to enable our network to give uncertainty together with detection results. The predicted uncertainty provides a continuous criterion to evaluate whether detection results are reliable. In addition, the uncertainty branch can lower the weight of ambiguous training samples, leading to more accurate detection results. We employ our proposed method in two typical practical applications. Edges of electrode sheets and pins of electronic chips are correctly detected as slender objects. Manufacturing quality is evaluated through analyzing the detection results, including keypoint number, displacement property, and uncertainty value.

Reliability of EEG microstate analysis at different electrode densities during propofol-induced transitions of brain states.

Electroencephalogram (EEG) microstate analysis is a promising and effective spatio-temporal method that can segment signals into several quasi-stable classes, providing a great opportunity to investigate short-range and long-range neural dynamics. However, there are still many controversies in terms of reproducibility and reliability when selecting different parameters or datatypes. In this study, five electrode configurations (91, 64, 32, 19, and 8 channels) were used to measure the reliability of microstate analysis at different electrode densities during propofol-induced sedation. First, the microstate topography and parameters at five different electrode densities were compared in the baseline (BS) condition and the moderate sedation (MD) condition, respectively. The intraclass correlation coefficient (ICC) and coefficient of variation (CV) were introduced to quantify the consistency of the microstate parameters. Second, statistical analysis and classification between BS and MD were performed to determine whether the microstate differences between different conditions remained stable at different electrode densities, and ICC was also calculated between the different conditions to measure the consistency of the results in a single condition. The results showed that in both the BS or MD condition, respectively, there were few significant differences in the microstate parameters among the 91-, 64-, and 32-channel configurations, with most of the differences observed between the 19- or 8-channel configurations and the other configurations. The ICC and CV data also showed that the consistency among the 91-, 64-, and 32-channel configurations was better than that among all five electrode configurations after including the 19- and 8-channel configurations. Furthermore, the significant differences between the conditions in the 91-channel configuration remained stable at the 64- and 32-channel resolutions, but disappeared at the 19- and 8-channel resolutions. In addition, the classification and ICC results showed that the microstate analysis became unreliable with fewer than 20 electrodes. The findings of this study support the hypothesis that microstate analysis of different brain states is more reliable with higher electrode densities; the use of a small number of channels is not recommended.

Effect of electrode characteristics on electromyographic activity of the masseter muscle.

OBJECTIVES: The study investigated effects of electrode material, inter-electrode distance (IED), and conductive gel on electromyographic (EMG) activity recorded from the masseter muscle. MATERIALS AND METHODS: EMG was recorded unilaterally, as ten volunteers performed standardized oral tasks. Ag/AgCl and Ag coated with Au were the gel-based; Ag alloy coated with graphene, pure Ag coated with graphene and silver nanowire embedded electrodes were the gel-free materials tested. Ag/AgCl electrodes were tested at three different IEDs (i.e. 15 mm, 20 mm, 25 mm). An electrode relative performance index (ERPI) was defined and calculated for each of the standardized oral tasks that the volunteers performed. ERPI values obtained for the different oral tasks with different electrode materials and IEDs were compared using two-way repeated-measures ANOVA. RESULTS: ERPI values were not significantly influenced by IED. However, for the electrode materials statistically significant differences were found in ERPI values for all oral tasks. Of the gel-free electrode materials tested, pure silver electrodes coated with graphene had the highest ERPI values followed by Ag alloy electrodes coated with graphene and silver nanowire embedded electrodes. CONCLUSIONS: Within the limitations of the study, IED between 15 and 25 mm has a negligible effect on masseter muscle EMG. Graphene coated and silver nanowire embedded electrodes show promise as gel-free alternatives.

Three-dimensional hierarchical porous carbon derived from lignin for supercapacitors: Insight into the hydrothermal carbonization and activation.

Three-dimensional hierarchical porous carbon is prepared by utilizing enzymatic hydrolysis lignin as a carbon source via hydrothermal carbonization and activation. The complicated operational parameters including temperature, time, concentration and pH in the hydrothermal carbonization are systemically investigated. We employed the hydrochar as electrode for supercapacitors. Accordingly, we not only achieve a high-performance specific capacitance for supercapacitors but also rationalize the effects of hydrothermal conditions on the specific capacitance via various characterizations. The activation process of hydrochar is also studied by comparing various activators and the activator/hydrochar ratios. The obtained materials possess a three-dimensional interconnected hierarchical structure with rational pore size distribution and a specific surface area reach up to 1504 m2 g-1. Then the corresponding supercapacitors achieve a large specific capacitance of 324 F g-1 as the current density is 0.5 A g-1. These supercapacitors acquire an outstanding cycling stability with 99.7% capacitance retention after 5000 cycles. The assembled symmetrical supercapacitors also show a high energy density of 17.9 W h kg-1 and can maintain at 5.6 W h kg-1 even at an ultra-high power density of 50,400 W kg-1.

Electrochemical immunosensor for determination of Staphylococcus aureus bacteria by IgY immobilized on glassy carbon electrode with electrodeposited gold nanoparticles.

A new ultrasensitive immunosensor is proposed based on the covalently attached anti-protein A antibody (IgY) on deposited gold nanoparticle (AuNP)-modified glassy carbon electrode (GCE) for the electrochemical measurement of Staphylococcus aureus (S. aureus). Chicken IgY as a capture antibody provides highly selective and specific binding to the target bacteria and selectively captures the S. aureus in its three-dimensional space. Due to that it can eliminate the interference from protein G-producing Streptococcus. In addition, the electron-transfer characteristic of [Fe(CN)6]4-/3- is hindered by this combination; as it is reflected on the electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) curves. The proposed immunosensor displays a wide linear dynamic range from 10 to 107 CFU mL-1 with a detection limit of 3.3 CFU mL-1 with RSD 3.0%. It is capable to accurately determine S. aureus in milk and human blood serum as a complex matrix sample with satisfactory recovery of ∼ 97-103%. The immunosensor also displays high selectivity over other bacteria and acceptable stability. Presumably, our study can be regarded as the first one to report chicken IgY in order to detect S. aureus based on an electrochemical method.Graphical abstract.

Intra- and inter-rater reliability of electrical impedance myography using adhesive electrodes in healthy volunteers.

In spite of the growing use of the electrical impedance myography (EIM) measures for clinical assessment and follow-up of diseased muscle tissue, reliability studies are scarce. We evaluate the reliability of the (EIM) technique using four adhesive electrodes over the muscle of interest. Intra- and inter-rater reliability was studied within the same session and between sessions. Thirty-one healthy and volunteer subjects aged between 20 and 26 years were recruited. Phase angle, reactance and resistance were assessed for each EIM measurement. Intraclass correlation coefficient (ICC) was used to determine the relative reliability. Absolute reliability was expressed as the standard error of measurement and the minimum detectable change. Relative reliability within the same session and between sessions for the EIM technique was excellent (ICCs > 0.9) concerning both intra- and inter-rater reliability, except for the component reactance. The absolute reliability was very high for the three EIM components. EIM measures using four adhesive electrodes over the area of interest is a reliable technique to assess muscle tissue status. This study confirms that these measurement results barely vary depending on the examiner and the moment. The present study also confirms phase angle as the least affected EIM component by examiner and evaluation moment.

EMG gait data from indwelling electrodes is attenuated over time and changes independent of any experimental effect.

The effect of time on the validity of electromyography (EMG) signals from indwelling fine-wire electrodes has not been explored. This is important because experiments using intramuscular electrodes are often long and biochemical and mechanical factors, may impair measurement accuracy over time. Measures over extended periods might therefore be erroneous. Twelve healthy participants (age = 33 ± 8 years) walked for 50 min at a controlled speed. Fine-wire electrodes were inserted into tibialis anterior and a surface EMG sensor attached near the fine-wire insertion site. EMG signals progressively and significantly decreased with time with the fine-wire electrode, but not the surface electrode. For the fine-wire electrode, after 25 min mean amplitude had reduced by 11% (p < 0.001) and after 50 min by 16% (p < 0.001), and peak amplitude reduced 22% at 20 min (p = 0.006) and 37% at 50 min (p < 0.001). Reduced amplitude with indwelling EMG without concurrent changes in surface EMG signal suggests an important inconsistency in data from fine-wire EMG electrodes. Changes in EMG signal will occur over time independent of the experimental condition and this questions their use in experiments of more than 30 min. These results should impact on experimental study design. They also invite reinterpretation of prior literature and sensor innovation to improve measurement performance.

Reconocimiento de tres patrones básicos de movimiento de la mano utilizando electromiografía de superficie y algoritmos inteligentes / Identification of three basic hand movement patterns by surface electromyography and smart algorithms

Introducción: este artículo presenta la predicción de tres tipos de movimientos básicos de la mano mediante un algoritmo inteligente para extraer características imprescindibles para el reconocimiento de patrones de movimiento a partir del análisis de señales electromiográficas superficiales adquiridas con el dispositivo Myo. Objetivo: reconocer y predecir patrones básicos de movimiento de la articulación del brazo utilizando electromiografía de superficie para aplicarlo sobre un prototipo de prótesis. Métodos: se tomaron datos de 13 estudiantes de 22 y 23 años de la Universidad Politécnica Salesiana, cada uno de los cuales ejecutó tres tipos de agarre: cilíndrico, pinza y pinza planar. Se trabajó con una frecuencia de 10 Hz y se tomaron 5 muestras por tipo de agarre durante 60 segundos. Para el análisis estadístico de los datos se utilizó la herramienta Anova, estableciendo un valor de significancia mayor a 0,65. Resultados: En ciertos voluntarios hay una mayor reacción en el electrodo 1 debido a que su antebrazo es mayor. El tiempo de respuesta para el reconocimiento varía dependiendo del número de variables que se tenga que comparar. Cuando se analiza un solo movimiento es de 2,6 segundos, en cambio, cuando se analizan los 3 movimientos el tiempo de respuesta incrementa a 7,8 segundos por la cantidad de electrodos que se quieran analizar. Conclusiones: la respuesta del sistema propuesto empieza a ser más lenta a medida que se analizan más movimientos a la vez y por tanto, es menos efectiva. El tiempo de ejecución y respuesta de nuestro sistema, en comparación al estado del arte, es más alto, debido a que se utilizan menos métodos de caracterización de la señal. Adicionalemtne, una limitante del proyecto es la frecuencia de muestreo del dispositivo Myo (200Hz)(AU)

Introduction: the paper presents the prediction of three basic hand movement types by means of a smart algorithm to draw characteristics indispensable for identification of movement patterns based on the analysis of surface electromyographic signals obtained with the Myo device. Objective: recognize and predict basic movement patterns of the arm joint using surface electromyography with a view to applying them over a prosthesis prototype. Methods: data were taken from 13 students aged 22 and 23 years from the Salesian Polytechnic University, each of whom performed three types of grasp: cylindrical, pincer and palmar pincer. A 10 Hz frequency was used and 5 samples were taken of each grasp type during 60 seconds. Statistical analysis was performed with the tool ANOVA, establishing a significance value > 0.65. Results: in certain volunteers a greater reaction was observed in electrode 1, due to their larger forearms. Response time for identification varies with the number of variables to be compared. When only one movement is analyzed, response time is 2.6 seconds, but when the three movements are examined it rises to 7.8 seconds by the number of electrodes intended to be studied. Conclusions: the response of the system proposed starts to slow down as more movements are analyzed simultaneously, which makes it less effective. The performance and response time of our system is higher than in state-of-the-art systems, since fewer signal characterization methods are used. On the other hand, a limitation of the project is the sampling frequency of the Myo device (200 Hz)(AU)

Neural selectivity, efficiency, and dose equivalence in deep brain stimulation through pulse width tuning and segmented electrodes.

BACKGROUND: Achieving deep brain stimulation (DBS) dose equivalence is challenging, especially with pulse width tuning and directional contacts. Further, the precise effects of pulse width tuning are unknown, and recent reports of the effects of pulse width tuning on neural selectivity are at odds with classic biophysical studies. METHODS: We created multicompartment neuron models for two axon diameters and used finite element modeling to determine extracellular influence from standard and segmented electrodes. We analyzed axon activation profiles and calculated volumes of tissue activated. RESULTS: We find that long pulse widths focus the stimulation effect on small, nearby fibers, suppressing distant white matter tract activation (responsible for some DBS side effects) and improving battery utilization when equivalent activation is maintained for small axons. Directional leads enable similar benefits to a greater degree. Reexamining previous reports of short pulse stimulation reducing side effects, we explore a possible alternate explanation: non-dose equivalent stimulation may have resulted in reduced spread of neural activation. Finally, using internal capsule avoidance as an example in the context of subthalamic stimulation, we present a patient-specific model to show how long pulse widths could help increase the biophysical therapeutic window. DISCUSSION: We find agreement with classic studies and predict that long pulse widths may focus the stimulation effect on small, nearby fibers and improve power consumption. While future pre-clinical and clinical work is necessary regarding pulse width tuning, it is clear that future studies must ensure dose equivalence, noting that energy- and charge-equivalent amplitudes do not result in equivalent spread of neural activation when changing pulse width.

Fast in vivo detection of myocardial norepinephrine levels in the beating porcine heart.

The sympathetic nervous system modulates cardiac function by controlling key parameters such as chronotropy and inotropy. Sympathetic control of ventricular function occurs through extrinsic innervation arising from the stellate ganglia and thoracic sympathetic chain. In the healthy heart, sympathetic release of norepinephrine (NE) results in positive modulation of chronotropy, inotropy, and dromotropy, significantly increasing cardiac output. However, in the setting of myocardial infarction or injury, sympathetic activation persists, contributing to heart failure and increasing the risk of arrhythmias, including sudden cardiac death. Methodologies for detection of norepinephrine in cardiac tissue are limited. Present techniques rely on microdialysis for analysis by high-performance liquid chromatography coupled to electrochemical detection (HPLC-ED), radioimmunoassay, or other immunoassays, such as enzyme-linked immunosorbent assay (ELISA). Although significant information about the release and action of norepinephrine has been obtained with these methodologies, they are limited in temporal resolution, require large sample volumes, and provide results with a significant delay after sample collection (hours to weeks). In this study, we report a novel approach for measurement of interstitial cardiac norepinephrine, using minimally invasive, electrode-based, fast-scanning cyclic voltammetry (FSCV) applied in a beating porcine heart. The first multispatial and high temporal resolution, multichannel measurements of NE release in vivo are provided. Our data demonstrate rapid changes in interstitial NE profiles with regional differences in response to coronary ischemia, sympathetic nerve stimulation, and alterations in preload/afterload.NEW & NOTEWORTHY Pharmacological, electrical, or surgical regulation of sympathetic neuronal control can be used to modulate cardiac function and treat arrhythmias. However, present methods for monitoring sympathetic release of norepinephrine in the heart are limited in spatial and temporal resolution. Here, we provide for the first time a methodology and demonstration of practice and rapid measures of individualized regional autonomic neurotransmitter levels in a beating heart. We show dynamic, spatially resolved release profiles under normal and pathological conditions.

Screen-Printed Electrodes Modified with Metal Nanoparticles for Small Molecule Sensing.

Recent progress in the field of electroanalysis with metal nanoparticle (NP)-based screen-printed electrodes (SPEs) is discussed, focusing on the methods employed to perform the electrode surface functionalization, and the final application achieved with different types of metallic NPs. The ink mixing approach, electrochemical deposition, and drop casting are the usual methodologies used for SPEs' modification purposes to obtain nanoparticulated sensing phases with suitable tailor-made functionalities. Among these, applications on inorganic and organic molecule sensing with several NPs of transition metals, bimetallic alloys, and metal oxides should be highlighted.

Computer simulation study on the effect of electrode-tissue contact force on thermal lesion size in cardiac radiofrequency ablation.

Purpose: In cardiac radiofrequency (RF) ablation, RF energy is often used to create a series of transmural lesions for blocking accessory conduction pathways. Electrode-tissue contact force (CF) is one of the key determinants of lesion formation during RF ablation. Low electrode-tissue CF is associated with ineffective RF lesion formation, whereas excessive CF may increase the risk of steam pop and perforation. By using finite element analysis, we studied lesion size and features at different values of electrode-tissue CF in cardiac RF ablation.Materials and methods: A computer-model-coupled electrode-tissue CF field, RF electric field, and thermal field were developed to study temperature distribution and lesion dimensions in cardiac tissue subjected to CF of 2, 5, 10, 20, 30, and 40 g with identical RF voltage and duration.Results: Increasing CF was associated with an increase in lesion depth, width, and cross-section area. The lesion cross-section area exhibited a linear increase, and the lesion width was significantly greater than lesion depth under the identical ablation condition. The relationship between CF value and lesion size is a power function: Lesion Size = a × CFb (Lesion Depth = 3.17 × CF0.14 and Lesion Width = 5.17 × CF0.14).Conclusions: This study confirmed that CF is a major determinant of RF lesion size and that electrode-tissue CF affects the amount of power dissipated in tissue. At a constant RF voltage and application time, RF lesion size increases as CF increases.

Introducing "Insertive Stripping Voltammetry": Electrochemical Determination of Sodium Ions Using an Iron(III) Phosphate-Modified Electrode.

A new type of stripping voltammetry is introduced, in which the preconcentration step includes ion insertion into a solid phase followed by a quantification step in which the ion is expelled via linear sweep voltammetry. Specifically, sodium-ion concentrations in both aqueous solution and synthetic sweat are electrochemically determined using iron(III) phosphate-modified glassy carbon electrodes. The electrochemical method consists of a potentiostatic step, holding the potential of -0.5 V vs saturated calomel electrode (SCE) for 100 s, followed by linear sweep voltammetry. It is shown that a thermal and mechanical pretreatment at 800 °C and with a ball mill, respectively, improve the electrochemical response of the iron(III) phosphate toward Na+. The involved structural and morphological changes were assessed by thermogravimetric analysis, scanning electron microscopy, and powder X-ray diffraction. The sensor exhibits a good selectivity toward Li+ and K+ and shows a linear response between 0.025 and 0.2 M Na+. As a proof-of-principle, the sensor was used to determine the sodium level in synthetic sweat.

Electrochemical treatment of organic pollutants in landfill leachate using a three-dimensional electrode system.

The use of three-dimensional electrode is a new electrochemical oxidation technology for landfill leachate treatment. In this study, a particle electrode was developed using Fe/C granules, which were suspended between the cathode and the anode to create a three-dimensional electrode. The three-dimensional electrode activated sodium persulfate to treat landfill leachate. Fe/C granules were prepared by incorporating iron filings and hydrothermally carbonized biochar into alginate beads. The optimal parameters of the three-dimensional electrode for chemical oxygen demand (COD) removal from landfill leachate were determined based on a series of single factor experiments as an operating voltage of 5 V, a sodium persulfate concentration of 28 mM, and 1 g of Fe/C granules. Treatment with the three-dimensional electrode at optimized conditions achieved 72.9% removal of COD and 99.9% removal of ammonia nitrogen, resulting in landfill leachate being clear and transparent. The changes in total organic carbon, nitrite, and nitrate concentrations indicated that most organic pollution and ammonia nitrogen were converted into CO2 and N2. This study provides an alternative technology for the treatment of refractory organic pollutants.