Search Results (679)

Cochlear implantation (CI) effectively restores hearing across the whole lifespan but may be followed by vestibular complaints, especially in adult recipients. The aim of this narrative review is to provide a comprehensive characterization of vestibular complaints after CI in adults, collecting clinical and instrumental data, as well as discussing the risk factors for their development. From data reported in the literature, we defined five recurring clinical presentations of postoperative vestibular disturbances (phenotypes): acute postoperative vestibular syndrome, benign paroxysmal positional vertigo (BPPV), delayed Ménière-like vertigo attributable to secondary endolymphatic hydrops, chronic postoperative disequilibrium, and stimulation-linked vertigo. According to the different pathogeneses underlying each presentation, the management of postoperative vestibular complaints should be phenotype-guided, including short-course vestibular suppressants and early mobilisation for acute presentations; canalith repositioning for BPPV; empiric therapy for hydropic-like episodes; and vestibular rehabilitation when imbalance is persistent, programming changes for stimulation-linked symptoms. Alongside this phenotype-driven approach, subjective symptoms are common across cohorts but are usually transient and persistent disability is uncommon. Furthermore, instrumental data across the studies indicate that objective abnormalities cluster in otolith and low-frequency canal measures: Cervical, ocular VEMP, and caloric responses are more often impaired than high-frequency canal function on vHIT, confirming histopathological studies showing preferential saccular involvement during the insertion of the electrode array. The risk of postoperative vestibular complaints not only appears to be modulated more by patient-related factors, especially pre-existing vestibular loss, but also by the aetiology of deafness, or age, rather than by device characteristics; atraumatic surgical approaches may further reduce this risk. This review emphasizes that future research on vestibular complaints after CI should adopt standardized phenotypes when evaluating symptoms, objective vestibular function, falls, and quality of life. Additionally, it should correlate these outcomes with hypothetical risk factors and detailed surgical reports. Full article

Transcutaneous electrical nerve stimulation (TENS) is constrained by high skin impedance and unstable electrode contact. This study proposes a novel composite electrode system comprising a polyvinyl alcohol/silver (PVA/Ag) microneedle array and a highly conductive polyacrylamide/lithium chloride (PAAm/LiCl) hydrogel. The PVA/Ag microneedles (~365 µm in height, ~48 µm tip diameter) possess sufficient mechanical strength to penetrate the stratum corneum, establishing a low-resistance pathway. The complementary PAAm/LiCl hydrogel exhibits high conductivity (10.28 S/m) and mechanical flexibility, further optimizing the interface contact. The experimental results demonstrate that this composite system achieves low electrochemical impedance and induces stable, clear electromyographic responses in vivo. It effectively addresses the common issues of electrode detachment and signal attenuation associated with conventional electrodes, offering a promising hardware solution for efficient and comfortable wearable rehabilitation devices. Full article

Electrochemiluminescence immunoassay (ECLIA) is widely used in clinical diagnostics owing to its high sensitivity, broad dynamic range, and excellent analytical stability. However, the influence of magnetic bead deposition behavior on electrochemiluminescence (ECL) signal performance remains insufficiently characterized. In this study, a quantitative evaluation method for magnetic bead distribution uniformity on the electrode surface was established and applied to optimize fluidic parameters in an ECLIA measurement system. By combining microscopic imaging with image analysis, magnetic bead spreading behavior under different flow conditions was systematically characterized and correlated with luminescence signal intensity. Optimization of the flow rate (18.46 µL·s⁻¹) improved bead distribution uniformity and resulted in a 26.32% increase in luminescence intensity without altering bead coverage or assay chemistry. The optimized system was further validated using thyroid-stimulating hormone (TSH) detection, showing a linear response over 0.016–120 µIU·mL⁻¹ (R² > 0.996) and high consistency with a commercial analyzer (R² = 0.998) from Roche. These results demonstrate that quantitative control of magnetic bead distribution provides an effective strategy for improving ECLIA performance and offers a general optimization framework for bead-based electrochemiluminescence systems. Full article

Background/Objectives: This study aimed to describe temporal trends in deep brain stimulation (DBS) use for Parkinson’s disease (PD), essential tremor (ET), and dystonia; characterize patient age and sex distribution and comorbidity; assess postoperative complications and in-hospital mortality (IHM) after implantation and explantation; and explore sex-specific differences in utilization and outcomes. Methods: We conducted a retrospective nationwide population-based study using the Spanish National Hospital Discharge Database (RAE-CMBD) from 2002 to 2019. All hospital admissions with DBS implantation or explantation/revision and a diagnosis of PD, ET, or dystonia were identified. Sociodemographic variables, the Charlson Comorbidity Index (CCI), length of hospital stay (LOHS), postoperative complications, and IHM were analyzed across three calendar periods and stratified by diagnosis and sex. Results: A total of 4883 admissions for DBS electrode implantations and 497 admissions for DBS explantation/revision were recorded. PD accounted for 82.6% of implantations, followed by ET (11.2%) and dystonia (6.3%). DBS activity increased significantly over time, while median LOHS declined from 12 to 6 days for implantations and from 13 to 5 days for explantations. Overall IHM after implantation was 0.27%, decreasing to 0.05% in 2014–2019; IHM after explantation was 0.6%. Most hospitalizations had low comorbidity (CCI = 0 in 87.8%), although comorbidity increased over time. Men represented approximately 60% of procedures in PD and ET. Women with PD underwent DBS at older ages, despite similar LOHS and IHM. Postoperative complications were recorded in 14.6% of implantations, mainly hardware-related issues (5–6%) and infections (1–2%), whereas infections (33%) and mechanical problems (27%) predominated among explantations. Conclusions: DBS use in Spain has expanded substantially, with shorter hospital stays and very low in-hospital mortality. Sex-related differences in utilization are increasing, and hardware complications and infections remain the most frequent conditions associated with explantation. As complications were identified only during the same hospitalization as the DBS procedure, late post-discharge events are not captured and could be underestimated; patient-level risks cannot be derived. Full article

High-resolution, multi-modal neural interfaces are essential for advancing systems neuroscience and brain–computer interface technologies. This study designed and fabricated a 128-channel comb-shaped flexible micro-electrode array. The device integrates a biocompatible Parylene substrate with a flexible thin-film microprobe array, enabling simultaneous recording of electrocorticography (ECoG), intracortical local field potentials (LFP), and neuronal action potentials (spikes) from the cortical surface and superficial layers. Microelectrode sites were modified with platinum black nanoparticles, significantly reducing impedance. In vivo experiments in rats demonstrated the array’s ability to capture high-fidelity signals across different recording depths. Key findings included the acquisition of opposing LFP trends and polarity reversals between adjacent channels, reflecting local microcircuit dynamics. The array also reliably recorded neural activity during audiovisual cross-modal sensory stimulation. These results validate the device as an effective tool for multi-scale electrophysiology, successfully balancing high spatial resolution and signal quality with minimal tissue invasiveness, thereby offering significant potential for fundamental research and neural engineering applications. Full article

This pilot EEG study examined the feasibility of a soundscape-based 40 Hz auditory stimulation format by using a soundscape-only condition as a contrast control. We tested whether a nature-based soundscape with an additively layered pure 40 Hz sine component (40 Hz ON; not amplitude-modulated) yields a more pronounced narrowband response centered at 40 Hz than the same soundscape without the 40 Hz layer (40 Hz OFF). Participants completed both conditions in a single-blind, randomized-order, within-participant crossover session with a washout interval. EEG outcomes included 40 Hz power, frequency-domain SNR around 40 Hz, scalp distribution of 40 Hz power, and phase-based connectivity in the gamma range. This study evaluates EEG-level detectability of 40 Hz–centered neural signatures and does not assess cognitive/clinical efficacy or therapeutic benefit. Across metrics, the 40 Hz ON soundscape showed a consistent ON > OFF directionality, including localized electrode-level signals and a temporal-region summary measure under nominal, uncorrected testing, accompanied by a clearer narrowband feature near 40 Hz in spectral profiles. Overall, the observed trends are consistent with the feasibility of embedding an additive 40 Hz layer into a naturalistic soundscape in a manner that yields EEG-quantifiable, 40 Hz centered signatures; however, because this is an exploratory pilot without multiplicity control, all effects should be interpreted as hypothesis-generating and warrant confirmation in larger, preregistered studies with multiplicity-aware inference. Full article

Peripheral nerve regeneration is most rapid during the early post-injury period but gradually slows over time, often limiting functional recovery. Electrical stimulation (ES) delivered via percutaneous needle electrodes has been shown to modulate the local neural microenvironment and promote axonal regeneration; however, the optimal temporal window and duration of stimulation remain unclear. This study aimed to evaluate the time-dependent effects of needle-based ES on peripheral nerve regeneration in a rat model of sciatic nerve transection, using a well-established silicone nerve conduit as a stable and reproducible non-biodegradable repair model. Female Sprague–Dawley rats underwent sciatic nerve transection and repair. Postoperatively (PO), animals were randomly assigned to control (C) needle insertion or needle-based ES groups, receiving stimulation for either 3 weeks (C-3W-PO and ES-3W-PO, respectively) or 7 weeks (C-7W-PO and ES-7W-PO, respectively). Functional recovery was evaluated using cold plate latency and rotarod performance tests. Electrophysiological assessments included measurements of nerve conduction velocity (NCV), compound muscle action potential amplitude, and muscle action potential (MAP) area. Histomorphometric analysis of regenerated nerve tissue quantified total nerve cross-sectional area, endoneurial space, axon number, and axon density. Retrograde labeling with fluoro-gold (FG) was used to quantify reinnervated motor neurons. Immunohistochemical analyses of calcitonin gene-related peptide (CGRP) and macrophage-associated markers were conducted to assess sensory neuropeptide expression and immune cell infiltration within the regenerated nerve. ES significantly improved both sensory and motor recovery in a duration-dependent manner. Behavioral data showed increased cold pain thresholds and improved motor coordination in ES groups, with the most pronounced functional gains observed in the ES-7W-PO group. Electrophysiological measures revealed higher NCV, amplitude, and MAP area in ES-treated animals, with the most pronounced improvements at 7 weeks. Morphologically, ES enhanced nerve regeneration, as evidenced by increased total and endoneurial areas, axonal counts, and axon density. FG-labeled neuron counts were significantly elevated in ES groups, indicating enhanced motor reinnervation. At 3 weeks, ES induced higher CGRP expression and macrophage density, suggesting transient activation of sensory-associated and pro-regenerative immune responses during the early post-injury phase. These findings demonstrate that ES accelerates peripheral nerve repair in rats and that sustained stimulation across the early regenerative window yields superior structural and functional outcomes. Full article

Background and Objectives: The aim of this retrospective study was to assess brachial plexus decompression throughout the sequential stages of the Roos procedure and to elucidate the role of first rib resection in the surgical management of Thoracic Outlet Syndrome (T.O.S). Materials and Methods: A total of 34 patients with a mean age of 34.6 years were included in this retrospective analysis. All patients underwent transaxillary first rib resection following anterior scalenotomy, consistent with the Roos procedure. Intraoperative brachial plexus functionality was assessed using recording electrodes for sensory and motor stimulation on the deltoid, biceps, triceps brachii, and abductor digiti minimi muscles. Mixed linear models with log-transformed data were used to assess changes in muscle measurements across surgical stages, with statistical significance at p less than 0.05. Results: The electromyographic values of the deltoid, biceps brachii, triceps brachii, and abductor digiti minimi muscles were significantly higher in the final post-operative neutral position compared to both the post-anterior scalenotomy and initial preoperative neutral positions. No significant differences were observed between the initial preoperative neutral position and the post-anterior scalenotomy values for these muscles. However, the abductor digiti minimi muscle exhibited a trend toward decreased values following anterior scalenotomy in comparison to the initial neutral position. Conclusions: Intraoperative outcomes of brachial plexus decompression during the Roos procedure demonstrate that first rib resection contributes to complete decompression of the relevant anatomical structures in Thoracic Outlet Syndrome. Full article

Steady-state visual evoked potentials (SSVEPs) are one of the key paradigms used in brain–computer interface (BCI) systems. Their performance, however, is substantially degraded by EEG artifacts of muscular, motion-related, and ocular origin. This issue is particularly pronounced in individuals exhibiting increased facial muscle tension or involuntary eye movements. The aim of this study was to develop and evaluate an EEG artifact reduction method based on auxiliary channels, including central (Cz), frontal (Fp1), electrooculographic (HEOG), and muscular electrodes (neck, cheek, jaw). Signals from these channels were used to model the physical sources of interference recorded concurrently with occipital brain activity (O1, O2, Oz). EEG signal cleaning was performed using linear regression in 1-s windows, followed by frequency-domain analysis to extract features related to stimulation frequencies and SSVEP classification using SVM and CNN algorithms. The experiment involved three visual stimulation frequencies (7, 8, and 9 Hz) generated by LEDs and the recording of controlled facial and jaw-related artifacts. Experiments conducted on 12 participants demonstrated a 9% increase in classification accuracy after artifact removal. Further analysis indicated that the Cz and jaw channels contributed most significantly to effective artifact suppression. The results confirm that the use of auxiliary channels substantially improves EEG signal quality and enhances the reliability of BCI systems under real-world conditions. Full article

Transcutaneous electrical nerve stimulation techniques (TENS) are rapidly gaining attention for their potential in various clinical applications. One such technique is transcutaneous auricular vagus nerve stimulation (taVNS), and it involves delivering nerve stimulation through the skin of the external ear. However, taVNS relies on electrodes that must conform to the complex anatomy of the ear while maintaining stable electrical performance. Conventional taVNS electrodes, typically rigid metal or adhesive pads, are uncomfortable, difficult to position, prone to drying, and costly to produce. Here, we present and evaluate two complementary fabrication approaches for soft dry electrodes suitable for taVNS, which are compliant with curved anatomical features and can be operated without gel. The first employs wet spinning of a conductive elastomer into fibers, while the second extends this method to create hollow cylindrical geometries. The resulting spongy polymer composite electrodes exhibit tunable geometry, high conductivity, mechanical resilience under strain and compression, and low material impedance confirmed through bench and human testing, even under dry conditions. These properties are critical for in-ear and broader transcutaneous stimulation applications, highlighting the potential of these fabrication methods for next-generation soft bioelectronic interfaces. Full article

Neural oscillations are fundamental to the integration of sensory, affective, and cognitive processes that contribute to pain perception. Transcranial alternating current stimulation (tACS) provides a valuable tool for investigating and modulating these oscillatory dynamics. In this review, we examine the effects of tACS on pain perception and pain-related oscillations in both healthy participants and individuals with chronic pain, highlighting methodological variability and mechanistic uncertainties that may contribute to mixed findings. We identified 14 studies, including 9 studies of experimental pain in healthy individuals and 5 of clinical pain disorders, comparing tACS to sham. Somatosensory alpha was the most frequently targeted oscillatory feature. Results varied considerably. Several studies reported reductions in pain, increases in alpha power, or changes in sensorimotor and prefrontal connectivity, but others showed no meaningful neural or behavioral effects. Out of the 14 studies, 6 demonstrated analgesic benefits and 2 showed improvements only under specific conditions or within subgroups, for a total of 8/14 studies with positive findings. Possible sources of heterogeneity include variation in stimulation duration, electrode montage, frequency alignment with individual rhythms, contextual state, and anatomical and neurophysiological differences across individuals. Pre-registered studies with sufficient power are needed to replicate effects within the most promising intervention protocols to establish a foundation in the field. We also recommend inclusion of brain imaging or electrophysiological recordings to verify whether stimulation effectively modulates the targeted neural oscillations. Finally, recent methodological advances, including phase-specific tACS, amplitude-modulated tACS, and individualized electric-field modeling, offer new opportunities to enhance mechanistic precision and clinical applicability. We argue that by integrating these approaches, future research can move beyond fixed, one-size-fits-all protocols toward personalized, state-dependent, closed-loop tACS approaches. Exploring these frontiers will transform tACS from an exploratory tool into a reliable intervention for pain. Full article

Background/Objectives: Amblyaudia (AMB) and dichotic dysaudia (DD) are distinct subtypes of dichotic listening deficits characterized by different behavioral profiles. AMB is associated with marked interaural asymmetry, whereas DD is defined by bilaterally poor but relatively symmetric performance. The present study investigated whether these behavioral distinctions are reflected in the auditory middle latency response (MLR). Specifically, we examined whether children with AMB exhibit asymmetric MLR patterns and whether children with DD demonstrate more symmetric responses, relative to typically performing (TYP) peers. Methods: Thirty-seven children aged 9–12 years with normal peripheral hearing were recruited through clinical referrals and community outreach. Participants were classified as AMB, DD, or TYP based on performance on standardized dichotic listening measures. MLRs were recorded in response to monaural click stimulation delivered to each ear at both slow and fast presentation rates. Peak-to-peak Na–Pa amplitude and latency were analyzed to assess ear- and electrode-related effects across groups. Results: Children with AMB showed significant ear effects, with larger Na–Pa amplitudes elicited by left-ear stimulation, particularly at electrode C4, consistent with their behavioral asymmetry. In contrast, the DD group exhibited minimal amplitude asymmetry but showed prolonged Na–Pa latencies for right-ear stimulation at faster presentation rates. TYP children demonstrated small, expected asymmetries without significant latency delays. No reliable electrode effects were observed across groups. Conclusions: The MLR differentiated between subtypes of dichotic listening deficits in ways that paralleled behavioral performance, with amplitude asymmetry characterizing AMB and rate-dependent latency differences observed in DD. These findings suggest that the MLR may provide complementary, objective information relevant to the characterization of distinct dichotic listening profiles in children. Full article

Poly(3,4-ethylenedioxythiophene)–polystyrene sulfonate (PEDOT:PSS) is widely used to fabricate conductive organic coatings for electrodes in electrophysiology. As these devices move toward clinical translation, establishing sterilization methods that preserve their functional properties is essential. Ethylene oxide (EtO) is routinely used for sterilizing heat- and moisture-sensitive medical devices due to its high penetration efficiency and low thermal load. However, the absence of systematic studies evaluating its impact on PEDOT:PSS raises concerns about the compatibility of EtO sterilization with organic electrophysiology interfaces. Here, we report the first comprehensive evaluation of EtO sterilization on PEDOT:PSS electrodes electrochemically deposited onto cortical interfaces designed for intraoperative monitoring and stimulation. EtO exposure induced only minimal changes in surface topography, with no detectable alteration of the electrical or electrochemical performance of the electrodes. Impedance spectroscopy, cyclic voltammetry, and charge-injection capacity measurements all revealed that EtO-treated electrodes retained properties comparable to untreated controls. Moreover, EtO-sterilized PEDOT:PSS coatings demonstrated robust long-term stability under accelerated lifetime testing, exhibiting negligible degradation over extended operation. These findings demonstrate that EtO sterilization is fully compatible with PEDOT:PSS-based bioelectronic interfaces and constitutes a viable pathway toward their safe and effective integration into clinical electrophysiology. This work represents an important step toward translating organic conducting polymer technologies into real-world biomedical applications. Full article

Background: Through the direct electrical stimulation of spiral ganglion neurons (SGNs) of the hearing nerve, cochlear implants overcome functionally impaired or missing hair cells in patients with profound to severe hearing loss. In routine clinical fitting, regions with severe local SGN degeneration (modiolar “dead regions”) cannot be identified. As a result, the electrical fields of neighboring electrodes are broadened, which can lead to increased channel interaction and, consequently, poorer speech understanding and hearing. The objective of this study was to ascertain whether neural health status can be evaluated by using cochlear implants’ inbuilt measures. Methods: Electrode impedance (MP1-, MP2-, MP1/MP2-, common ground mode), transimpedance matrix (TIM) and electrically evoked compound action potential (eCAP) measurements were performed before and after laser-induced induction of lesions on the modiolus of the guinea pig. Laser treatment-related shifts in impedance, TIM, and eCAP characteristics (threshold, amplitude, and a modified version of the failure index, referred to as the efficiency index (EI)) were correlated with the histologically assessed damage in three predefined areas of the basal modiolus within the electrode region. Results: Modiolar damage resulted in a significant reduction in the electrode impedance in MP2- and MP1/2-mode, the eCAP amplitude, and the EI. In contrast, TIM values and eCAP thresholds were significantly elevated. MP1, MP1/MP2 electrode impedance, TIM, and the eCAP thresholds were not correlated with the extent of modiolar damage. The shifts in eCAP amplitudes and the EI were significantly correlated with the damage at all regions of the basal modiolus. Conclusions: The eCAP amplitude and the EI are both capable of objectively evaluating the neural health status of the cochlea. Thus, a modiolar dead region could be expected from a local drop in eCAP amplitude values or the modified EI within the electrode array. Full article

The integration of complementary metal–oxide–semiconductor (CMOS) and micro-electromechanical systems (MEMSs) technologies for miniaturized biosensor fabrication enables unprecedented spatiotemporal resolution in monitoring the bioelectrical activity of the nervous system. Wafer-level CMOS technology incurs high costs, but multi-project wafer (MPW) runs mitigate this by allowing multiple users to share a single wafer. Still, monolithic CMOS biosensors require specialized surface materials or device geometries incompatible with standard CMOS processes. Performing MEMS post-processing on the few square millimeters available in MPW dies remains a significant challenge. In this paper, we present a MEMS post-processing workflow tailored for CMOS dies that supports both surface material modification and layout shaping for intracortical biosensing applications. To address lithographic limitations on small substrates, we optimized spray-coating photolithography methods that suppress edge effects and enable reliable patterning and lift-off of diverse materials. We fabricated a needle-like, 512-channel simultaneous neural recording active pixel sensor (SiNAPS) technology based neural probe designed for integration with optical fibers for optogenetic studies. To mitigate photoelectric effects induced by light stimulation, we incorporated a photoelectric shield through simple modifications to the photolithography mask. Optical bench testing demonstrated >96% light-shielding effectiveness at 3 mW of light power applied directly to the probe electrodes. In vivo experiments confirmed the probe’s capability for high-resolution electrophysiological measurements. Full article