Electrode Position Research Articles

Personalized topology-informed localization of standard 12-lead ECG electrode placement from incomplete cardiac MRIs for efficient cardiac digital twins.

Cardiac digital twins (CDTs) offer personalized in-silico cardiac representations for the inference of multi-scale properties tied to cardiac mechanisms. The creation of CDTs requires precise information about the electrode position on the torso, especially for the personalized electrocardiogram (ECG) calibration. However, current studies commonly rely on additional acquisition of torso imaging and manual/semi-automatic methods for ECG electrode localization. In this study, we propose a novel and efficient topology-informed model to fully automatically extract personalized ECG standard electrode locations from 2D clinically standard cardiac MRIs. Specifically, we obtain the sparse torso contours from the cardiac MRIs and then localize the standard electrodes of 12-lead ECG from the contours. Cardiac MRIs aim at imaging of the heart instead of the torso, leading to incomplete torso geometry within the imaging. To tackle the missing topology, we incorporate the electrodes as a subset of the keypoints, which can be explicitly aligned with the 3D torso topology. The experimental results demonstrate that the proposed model outperforms the time-consuming conventional model projection-based method in terms of accuracy (Euclidean distance: 1.24±0.293 cm vs. 1.48±0.362 cm) and efficiency (2 s vs. 30-35 min). We further demonstrate the effectiveness of using the detected electrodes for in-silico ECG simulation, highlighting their potential for creating accurate and efficient CDT models. The code is available at https://github.com/lileitech/12lead_ECG_electrode_localizer.

Emerging evidence on the effects of electrode arrangements and other parameters on the application of transcutaneous spinal direct current stimulation.

Transcutaneous spinal direct current stimulation (TSDCS) has the potential to modulate spinal circuits and induce functional changes in humans. Nevertheless, differences across studies on basic parameters used and obtained metrics represent a confounding factor. Computer simulations are instrumental in improving the application of the TSDCS technique. Their findings allow a better interpretation of the tissue conductivities heterogeneity. Emerging findings indicate the electric field is maximal in the segments located between the electrodes and that factors such as the depth of the targeted area, and location of the electrodes on low conductive points, such as the spinous processes, may impact the electric field generated in the spinal cord, with consequences for thoracic versus lumbar or cervical applications. Recently, growing attention has been directed toward the importance of the TSDCS reference electrode's position and its influence on the current field properties at the targeted site. This review highlights the influence of dosage, polarity, and electrode position on the variety of TSDCS results in healthy and some clinical populations. Based on the available evidence, we suggest that although the current dosage appears to have a negligible effect, the variety of electrode montages and configurations of TSDCS can significantly impact the electric field distributions and potentially explain the conflicting results of experimental studies. Future human trials should systematically and thoughtfully evaluate the location of TSDCS electrodes based on the targeted neural structures.

EMG Dataset for Gesture Recognition with Arm Translation

Myoelectric control has emerged as a promising approach for a wide range of applications, including controlling limb prosthetics, teleoperating robots and enabling immersive interactions in the Metaverse. However, the accuracy and robustness of myoelectric control systems are often affected by various factors, including muscle fatigue, perspiration, drifts in electrode positions and changes in arm position. The latter has received less attention despite its significant impact on signal quality and decoding accuracy. To address this gap, we present a novel dataset of surface electromyographic (EMG) signals captured from multiple arm positions. This dataset, comprising EMG and hand kinematics data from 8 participants performing 6 different hand gestures, provides a comprehensive resource for investigating position-invariant myoelectric control decoding algorithms. We envision this dataset to serve as a valuable resource for both training and benchmark arm position-invariant myoelectric control algorithms. Additionally, to expand the publicly available data capturing the variability of EMG signals across diverse arm positions, we propose a novel data acquisition protocol that can be utilized for future data collection.

Does the audiogram shape influence the intracochlear recording of Electrocochleography during and after cochlear implantation?

During cochlear implant (CI) surgery, it is desirable to perform intraoperative measurements such as Electrocochleography (ECochG) to monitor the inner ear function and thereby to support the preservation of residual hearing. However, a significant challenge arises as the recording location of intracochlear ECochG via the CI electrode changes during electrode insertion. This study aimed to investigate the relationships between intracochlear ECochG recordings, the position of the recording contact within the cochlea relative to its anatomy, and the implications for frequency and residual hearing preservation. Intraoperative ECochG recordings were conducted using the CI electrode (MED-EL) during the insertion of hearing preservation electrodes and after the insertion process. Recordings were continuously conducted using the most apical electrode (contact 1) during insertion. After insertion, the recordings were performed on all different electrode contacts. The electrode location in the cochlea during insertion was estimated using mathematical models and preoperative clinical imaging, while the postoperative electrode position was determined using postoperative clinical imaging. The study involved 10 adult CI recipients. In those with good low-frequency hearing, an increase in signal amplitude was observed, with the highest amplitudes closest to the stimulation frequency generators, and no phase change was observed. Conversely, patients with flat hearing loss exhibited a second peak with an opposite phase in the medial area of the cochlea. This study is the first to suggest that the pattern of the preoperative audiogram may influence the ECochG outcomes measured intraoperatively. Specifically, the ECochG responses during insertion appeared to behave as expected with good low-frequency hearing, while with flat hearing loss there appear to be further effects. These findings indicate that this approach can provide valuable information for the interpretation of intracochlearly recorded ECochG signals.

Technical validation of the Zeto wireless, dry electrode EEG system.

Objective.Clinical adoption of innovative EEG technology is contingent on the non-inferiority of the new devices relative to conventional ones. We present the four key results from testing the signal quality of Zeto's WR 19 EEG system against a conventional EEG system conducted on patients in a clinical setting.Methods.We performed 30 min simultaneous recordings using the Zeto WR 19 (zEEG) and a conventional clinical EEG system (cEEG) in a cohort of 15 patients. We compared the signal quality between the two EEG systems by computing time domain statistics, waveform correlation, spectral density, signal-to-noise ratio and signal stability.Results.All statistical comparisons resulted in signal quality non-inferior relative to cEEG. (i) Time domain statistics, including the Hjorth parameters, showed equivalence between the two systems, except for a significant reduction of sensitivity to electric noise in zEEG relative to cEEG. (ii) The point-by-point waveform correlation between the two systems was acceptable (r>0.6; P<0.001). (iii) Each of the 15 datasets showed a high spectral correlation (r>0.99; P<0.001) and overlapping spectral density across all electrode positions, indicating no systematic signal distortion. (iv) The mean signal-to-noise ratio (SNR) of the zEEG system exceeded that of the cEEG by 4.82 dB, equivalent to a 16% improvement. (v) The signal stability was maintained through the recordings.Conclusion.In terms of signal quality, the zEEG system is non-inferior to conventional clinical EEG systems with respect to all relevant technical parameters that determine EEG readability and interpretability. Zeto's WR 19 wireless dry electrode system has signal quality in the clinical EEG space at least equivalent to traditional cEEG recordings.

Transcranial electrical evoked muscle potentials for pediatric neurosurgery: scoping review of stimulation techniques and success rates.

The background of this scoping review is that pediatric neurosurgery in the vicinity of motor pathways is associated with the risk of motor tract damage. By measuring transcranial electrical evoked potentials in muscles (electromyogram) or from the spinal cord (epidural D-wave) functional disorders and impending damage can be detected during surgery and countermeasures can be initiated. The objective was to summarize stimulation techniques of transcranial electrical stimulation and the success rate of motor evoked potentials exclusively in children undergoing neurosurgery. The data source was a literature search for reports meeting the suitability criteria (original articles and case series including motor evoked potentials and pediatric neurosurgery). Twenty-four articles meeting suitability criteria were retrieved. The most common primary electrode positions for electrical stimulation were at C3 vs. C4 and C1 vs. C2 according to the 10-20-system of EEG. Single trains of 1 to 9 pulses with voltages from 160 to 900V and pulse durations from 50 to 500µs were applied for voltage-controlled stimulation. Interstimulus intervals ranged from 0.1 to 9.9ms. Signals were filtered with high-pass filters between 1.5 and 300Hz and low-pass filters between 500 and 5000Hz. The overall rate of successful stimulation and measurement was 90.5% (N = 769). A broad range of stimulation parameters was used for transcranial electrical evoked potentials. Measurable potentials were obtained in most patients. Consideration of safety precautions is an important implication to avoid adverse events by application of high voltage to the motor cortex.

Electromagnetic tracking system for position and orientation detection of deep brain stimulation electrodes during surgery

Electromagnetic tracking system for position and orientation detection of deep brain stimulation electrodes during surgery

The role of intraoperative monitoring in target selection in deep brain stimulation: A single centre study.

Intraoperative microelectrode recording (MER) and intraoperative test stimulation may provide vital information for optimal electrode placement and clinical outcome in movement disorders patients treated with deep brain stimulation (DBS). The aims of this retrospective study were to determine (i) how often the planned (imaging based) placements of electrodes were changed due to MER and intraoperative test stimulation in Parkinson's disease (PD), dystonia and essential tremor (ET) patients; (ii) whether the frequency of repositioning changed over time; (iii) whether patients' age or disease duration (in PD) influenced the frequency of repositioning. Data on the planned and the final placement of 141 electrodes in 72 consecutive DBS treated patients (52 PD, 11 dystonia, 9 ET) was collected over the first 8years of DBS implementation in a single center. An association between the rate of electrode repositioning and the patients' age, disease duration and the time/year of implementation was explored. Analysis of all targets showed a change in final electrode placement in 39.7% (56/141); 39.8% (41/103) in PD, 40.9% (9/22) in dystonia and 37.5% (6/16) in ET. Annual analysis showed a decrease in rate of repositioning between the centre's first and eighth year (p=0.013) of implementation. No correlation was found between electrode repositioning rate and patient age (p=0.42) nor disease duration (p=0.09) in PD. This retrospective analysis confirms the benefit of MER and intraoperative test stimulation during DBS surgery in determining the final electrode position during the early / initial period of implementing the procedure. Our findings show a learning curve in successful preoperative planning in our centre achieved through experience.

PreVISE: an efficient virtual reality system for SEEG surgical planning.

Epilepsy is a neurological disorder characterized by recurring seizures that can cause a wide range of symptoms. Stereo-electroencephalography (SEEG) is a diagnostic procedure where multiple electrodes are stereotactically implanted within predefined brain regions to identify the seizure onset zone, which needs to be surgically removed or disconnected to achieve remission of focal epilepsy. This procedure is complex and challenging due to two main reasons. First, as electrode placement requires good accuracy in desired brain regions, excellent knowledge and understanding of the 3D brain anatomy is required. Second, as typically multiple SEEG electrodes need to be implanted, the positioning of intracerebral electrodes must avoid critical structures (e.g., blood vessels) to ensure patient safety. Traditional SEEG surgical planning relies on 2D display of multi-contrast volumetric medical imaging data, and places a high cognitive demand for surgeons' spatial understanding, resulting in potentially sub-optimal surgical plans and extensive planning time (~ 15 min per electrode). In contrast, virtual reality (VR) presents an intuitive and immersive approach that can offer more intuitive visualization of 3D data as well as potentially enhanced efficiency for neurosurgical planning. Unfortunately, existing VR systems for SEEG surgery only focus on the visualization of post-surgical scans to confirm electrode placement. To address the need, we introduce the first VR system for SEEG planning that integrates user-friendly and efficient visualization and interaction strategies while providing real-time feedback metrics, including distances to nearest blood vessels, angles of insertion, and the overall surgical quality scores. The system reduces the surgical planning time by 91%.

Positioning of the dispersive electrode and its effect on the safety and efficacy of radiofrequency ablation.

Positioning of the dispersive electrode and its effect on the safety and efficacy of radiofrequency ablation.

Optic nerve-mediated modulation of temporally interfering electric fields for potential targeted retinal disease therapy: a computational modeling study

IntroductionTraditional extraocular electrical stimulation typically produces diffuse electric fields across the retina, limiting the precision of targeted therapy. Temporally interfering (TI) electrical stimulation, an emerging approach, can generate convergent electric fields, providing advantages for targeted treatment of various eye conditions.ObjectiveUnderstanding how detailed structures of the retina, especially the optic nerve, affects electric fields can enhance the application of TI approach in retinal neurodegenerative and vascular diseases, an essential aspect that has been frequently neglected in previous researches.MethodsWe developed an anatomically accurate multi-layer human eye model, incorporating the optic nerve segment and setting it apart from current research endeavors. Based on this model, we conducted in silico investigations to predict the influence of the optic nerve on spatial characteristics of the temporally interfering electric field (TIEF) generated by diverse electrode configurations.ResultsOptic nerve directly influenced spatial distributions and modulation rules of TIEFs. It caused convergent areas to shift nasally or temporally in relation to return electrode positions, and further increased the axial anisotropy within the convergent TIEF. Furthermore, alterations in electrode positions and adjustments to current ratios among channels induced diverse spatial patterns of TIEFs within the macular region, the area surrounding the optic nerve, as well as peripheral retina.ConclusionOur findings suggested that presence of the optic nerve necessitated the utilization of different modulating paradigms when employing TI strategy for targeted treatment of various retinal lesions. And also provided theoretical references for developing a novel retinal electrical stimulation therapeutic device based on TI technology.

A Leadfield-Free Optimization Framework for Transcranially Applied Electric Currents.

Transcranial Electrical Stimulation (TES), Temporal Interference Stimulation (TIS), Electroconvulsive Therapy (ECT) and Tumor Treating Fields (TTFields) are based on the application of electric current patterns to the brain. The optimal electrode positions, shapes and alignments for generating a desired current pattern in the brain vary between persons due to anatomical variability. The aim is to develop a flexible and efficient computational approach to determine individually optimal montages based on electric field simulations. We propose a leadfield-free optimization framework that allows the electrodes to be placed freely on the head surface. It is designed for the optimization of montages with a low to moderate number of spatially extended electrodes or electrode arrays. Spatial overlaps are systematically prevented during optimization, enabling arbitrary electrode shapes and configurations. The approach supports maximizing the field intensity in target region-of-interests (ROI) and optimizing for a desired focality-intensity tradeoff. We demonstrate montage optimization for standard two-electrode TES, focal center-surround TES, TIS, ECT and TTFields. Comparisons against reference simulations are used to validate the performance of the algorithm. The system requirements are kept moderate, allowing the optimization to run on regular notebooks and promoting its use in basic and clinical research. The new framework complements existing optimization methods that require small electrodes, a predetermined discretization of the electrode positions on the scalp and work best for multi-channel systems. It strongly extends the possibilities to optimize electrode montages towards application-specific aims and supports researchers in discovering innovative stimulation schemes. The framework is available in SimNIBS.

Cost-Effective Bioimpedance Spectroscopy System for Monitoring Syncytialization In Vitro: Experimental and Numerical Validation of BeWo Cell Fusion.

The placenta plays a critical role in nutrient and oxygen exchange during pregnancy, yet the effects of medicinal drugs on this selective barrier remain poorly understood. To overcome this, this study presents a cost-effective bioimpedance spectroscopy (BIS) system to assess tight junction integrity and monolayer formation in BeWo b30 cells, a widely used model of the multinucleated maternal-fetal exchange surface of the placental barrier. Cells were cultured on collagen-coated porous membranes and treated with forskolin to induce controlled syncytialization. Electrical impedance was measured using an entry level impedance analyzer, while immunofluorescence staining was used to confirm monolayer formation and syncytialization. The measurements and staining confirmed the formation of a confluent monolayer on day 4. In fact, the electrical resistance tripled for treated samples indicating a more electrically restrictive barrier. This resistance remained constant for treated samples reflecting the intact barrier's integrity over the next 3 days. The measurements show that, on day 4, the electrical capacitance of the cells decreased for the treated samples as opposed to the untreated samples. This reflects that the surface area of the BeWo b30 cells decreased when the samples were treated with forskolin. Finally, a COMSOL model was developed to explore the effects of electrode positioning, depth, and distance on TEER measurements, explaining discrepancies in the literature. In fact, there was a substantial 97% and 39.4% difference in the obtained TEER values. This study demonstrates the AD2 device's feasibility for monitoring placental barrier integrity and emphasizes the need for standardized setups for comparable results. The system can hence be used to analyze drug effects and nutrient transfer across the placental barrier.

Precision of Intraoperative Cone-Beam Computed Tomography in Electrode Placement and Complications in Asleep Deep Brain Stimulation Surgery: A Multidetector Computed Tomography-Verified Comparative Study.

Successful deep brain stimulation (DBS) requires precise electrode placement. However, brain shift from loss of cerebrospinal fluid or pneumocephalus still affects aim accuracy. Multidetector computed tomography (MDCT) provides absolute spatial sensitivity, and intraoperative cone-beam computed tomography (iCBCT) has become increasingly used in DBS procedures. However, its accuracy is unclear. We examined iCBCT accuracy and the need for postoperative imaging to confirm electrode position and assess complications of DBS surgery. Thirty-two movement disorder patients, and 69 targets were retrospectively reviewed. All patients had preoperative non-stereotactic 3.0 Tesla magnetic resonance imaging (MRI), preoperative stereotactic MDCT, post-implantation iCBCT, and postoperative conventional MDCT scans. Stereotactic coordinates of electrode tips were compared between postoperative MDCT and iCBCT. We calculated the absolute and Euclidian differences (ED) between iCBCT and postoperative MDCT coordinates for each electrode. To assess whether intraoperative brain shifting influenced electrode tip localisation, subdural pneumocephalus volume was measured in iCBCT images. The mean absolute (scalar) differences in x, y, and z coordinates were not significantly different from the absolute precision value of 0 (p 0.05). The mean ED between the iCBCT electrode tip and the postoperative MDCT electrode tip coordinates was 1mm (0.55±0.03 mm) and differed significantly from zero (p 0.0001). There was no correlation between pneumocephalus volume and electrode coordinate deviation. iCBCT can eliminate the need for routine postoperative studies since it is a safe, effective, and rapid procedure that can be performed at any step of the surgery. It provides reliable and definitive confirmation of correct DBS electrode placement.

Frequency-to-Place Mismatch and Cochlear Implant Outcomes by Electrode Type

Speech recognition outcomes with a cochlear implant (CI) are highly variable. One factor suggested to correlate with CI-aided speech recognition is frequency-to-place mismatch, or the discrepancy between the natural tonotopic organization of the cochlea and the electric frequency allocation of the CI electrodes within the patient's cochlea. To evaluate the association between frequency-to-place mismatch and speech recognition outcomes in a large cohort of postlingually deafened adult CI users, while controlling for various clinical factors known to be associated with those outcomes. This retrospective cohort study used data from a CI program at a tertiary medical center and included CIs from postlingually deafened adult CI users. After excluding patients whose data were not logged, patients with implantations occurring between 2016 and 2023 were included in the analysis. The data were extracted in November 2023. Results of the Consonant-Nucleus-Consonant (CNC) monosyllabic word recognition test measured in the CI-aided alone condition 1 month, 3 months, 6 months, and 12 months after activation served as the main outcome. The independent variables included frequency-to-place mismatch, electrode array type, mean modiolar distance, electrode position, age at implantation, biological sex, contralateral hearing abilities, time since CI activation (test interval), and daily device use. In 498 CIs from 447 postlingually deafened adults (mean [SD] age, 63.1 [17.1] years; 271 [54.4%] CIs with male users), frequency-to-place mismatch was negatively correlated with CI-aided speech recognition outcomes, but the association was only significant for precurved electrode arrays and not straight electrode arrays. In the linear mixed effects model for straight electrode arrays, only test interval (β = 1.14 [95% CI, 0.90-1.38]) and daily device use (β = 0.90 [95% CI, 0.42-1.38]) were correlated with the improvement of word recognition over the first year of device use. In the model for precurved electrode arrays, mismatch at 1500 Hz (β = -0.011 [95% CI, -0.011 to -0.006]), scalar location (β = 16.37 [95% CI, 9.01 to 23.74]), test interval (β = 1.18 [95% CI, 1.18-1.41]) and daily device use (β = 1.65 [95% CI, 1.15-2.14]) all were significantly associated with the improvement of word recognition over the first year of device use. In this cohort study of postlingually deafened adult CI users, including both straight and precurved electrode arrays, daily device use and time since CI activation were found to be significantly associated with improved CI-aided speech recognition outcomes. Frequency-to-place mismatch at 1500 Hz and scalar location were associated with word recognition only for precurved arrays. These findings suggest that, for patients with straight arrays, any interference produced by frequency-to-place mismatch may be overcome by adaptation, which could be supported by daily device use. However, for patients with precurved arrays, daily device use may not be sufficient to completely overcome electrode placement factors, including scalar location and mismatch.

Head and shoulders—The impact of an extended head model on the simulation and optimization of transcranial electric stimulation

Abstract Electric field calculations are increasingly used for dose characterization of transcranial electrical stimulation (tES), but existing open-source head models are inaccurate for extracephalic montages that include electrodes placed on the neck or shoulder. We introduce the “Ernie Extended” model, an MRI- and CT-derived open-source head model extending to the upper shoulder region. Simulations of extracephalic tES targeting the cerebellum and supplementary motor area show significant differences in electric fields when using Ernie Extended compared to the non-extended Ernie model. Additionally, we propose an electrode layout that complements the electroencephalography 10–20 system with extracephalic electrode positions. We demonstrate the use of this layout for optimizing multi-electrode tES montages for cerebellar stimulation, enhancing focality, and reducing off-target stimulation, particularly of the spinal cord. Our results highlight the practical value of the Ernie Extended model for accurately characterizing doses produced by extracephalic tES montages and when targeting more caudal brain regions.

Electrode contact estimation based on preoperative versus postoperative imaging as a basis for anatomy-based fitting

Abstract Anatomy-based fitting (ABF) has the potential to lead to better outcomes than conventional clinically-based fitting (CBF). It has already been shown that anatomy-based fitting based on postoperative imaging (postopABF) can improve speech understanding. Moreover, it was demonstrated that patients preferred anatomy-based fitting maps based on preoperative imaging (preop ABF) over CBF. The goal of this study was to examine if a difference between preopABF and postopABF could be observed. Via the software OTOPLAN4 (CAScination, MED-EL) the electrode position was calculated based on preoperatively, as part of the clinical routine, obtained imaging (CT or MRI). If necessary, after the cochlear implantation surgery the selected electrode array was adapted if a different array was chosen intraoperatively. This data was exported into the fitting software MAESTRO to enable a preopABF. The same process was done based on postoperative imaging (CT) so that 1) the frequency bands were compared between preopABF and postopABF data and 2) the difference was displayed in semitones. 27 Patients could be included who got a postoperative CT scan. In addition, subjective tinnitus and dizziness or imbalance issues did not significantly change from the pre-operative appointment over the first fitting to the control fitting one month later. In this study, we could show that there is no significant difference between apical to medial and a significant difference for medial to basal electrode contacts between the preopABF and postopABF regarding the frequency bands. Thus, preopABF is an easy, clinically practicable way to implement ABF, which is promising to lead to better outcomes without extra costs and the radiation burden that comes with postopABF. If patients subjectively prefer either preopABF or postopABF is still to be examined.

EFFECTS OF TRANSCRANIAL DIRECT CURRENT STIMULATION (tDCS) ASSOCIATED WITH BALANCE TRAINING IN INDIVIDUALS WITH PARKINSON'S: STUDY PROTOCOL FOR A RANDOMIZED CLINICAL TRIAL

The present study aimed to investigate the effects of balance training associated with cerebellar tDCS on postural control in individuals with PD. This is a randomized clinical trial in which individuals were allocated to an experimental group (EG) or placebo group (PG), in which a conventional protocol of 10 Physiotherapy sessions for locomotor training and postural control was applied. In the EG, tDCS was applied, with a current setting of 1.5 mA for 20 minutes simultaneously with postural control training. In the PG, tDCS was applied in sham mode, with the same electrode positioning and the same number of sessions as the EG. The sample compared 34 individuals with PD (EG: 17; PG: 17).Cerebellar tDCS associated with balance training may help improve postural control and balance in walkers with Parkinson's Disease. The hypothesis is, if walking improve, the benefits may be accompanied by better balance and reduced fear of falling, and individuals may experience greater free-living physical activity at home and in the community.

Selective Auditory Attention Detection Using Combined Transformer and Convolutional Graph Neural Networks.

Attention is one of many human cognitive functions that are essential in everyday life. Given our limited processing capacity, attention helps us focus only on what matters. Focusing attention on one speaker in an environment with many speakers is a critical ability of the human auditory system. This paper proposes a new end-to-end method based on the combined transformer and graph convolutional neural network (TraGCNN) that can effectively detect auditory attention from electroencephalograms (EEGs). This approach eliminates the need for manual feature extraction, which is often time-consuming and subjective. Here, the first EEG signals are converted to graphs. We then extract attention information from these graphs using spatial and temporal approaches. Finally, our models are trained with these data. Our model can detect auditory attention in both the spatial and temporal domains. Here, the EEG input is first processed by transformer layers to obtain a sequential representation of EEG based on attention onsets. Then, a family of graph convolutional layers is used to find the most active electrodes using the spatial position of electrodes. Finally, the corresponding EEG features of active electrodes are fed into the graph attention layers to detect auditory attention. The Fuglsang 2020 dataset is used in the experiments to train and test the proposed and baseline systems. The new TraGCNN approach, as compared with state-of-the-art attention classification methods from the literature, yields the highest performance in terms of accuracy (80.12%) as a classification metric. Additionally, the proposed model results in higher performance than our previously graph-based model for different lengths of EEG segments. The new TraGCNN approach is advantageous because attenuation detection is achieved from EEG signals of subjects without requiring speech stimuli, as is the case with conventional auditory attention detection methods. Furthermore, examining the proposed model for different lengths of EEG segments shows that the model is faster than our previous graph-based detection method in terms of computational complexity. The findings of this study have important implications for the understanding and assessment of auditory attention, which is crucial for many applications, such as brain-computer interface (BCI) systems, speech separation, and neuro-steered hearing aid development.

Vestibular electrode position stability over time.

In vestibular implants (VI), the electrode position is thought to be important for optimal neural activation. The objective of this study was to evaluate the stability of the vestibular electrode position over time. Seven patients implanted with a VI were followed for one year. When possible, the fenestrations of the semicircular canals were kept very small (approximately 0.8mm) to stabilize the electrode lead. Additionally, the electrodes were fixed at their fenestration sites using bone cement. A temporal bone CT scan was performed intraoperatively, and one week and one year postoperatively. In one patient reliable analysis of the intraoperative CT scan was not possible due to a technical error. A displacement of the vestibular electrodes of more than 0.5mm was considered significant. Fourteen out of 18 electrodes did not show a significant displacement between the intraoperative scan and the first postoperative scan. In the remaining four electrodes, a displacement of ≥ 0.5mm occurred (mean 0.54mm, range 0.50-0.58mm). These four electrodes were found in the two first implanted patients. In both cases, the intraoperative CT scan had a slice thickness of 0.5mm and showed severe scattering. This might imply that the measured displacement was (partially) related to a higher measurement error. None of the vestibular electrodes migrated outside of the ampulla. No displacement was observed in any of the vestibular electrodes between the first postoperative scan and the one-year follow-up scan. The current surgical technique seems to securely stabilize the vestibular VI electrodes over time.