Search Results (139)

The development of implantable neural interfaces is essential for enabling bidirectional communication between the nervous system and prosthetic devices, yet their evaluation still relies primarily on in vivo models which are costly, variable, and ethically constrained. Here, we report a bio-inspired artificial nerve simulator engineered as a reproducible ex vivo platform for pre-implantation testing of plug-type electrodes. The simulator is fabricated from a conductive hydrogel composite based on reduced graphene oxide (rGO), polyaniline (PANI), agarose, sucrose, and sodium chloride, with embedded conductive channels that replicate the fascicular organization and conductivity of peripheral nerves. The resulting construct exhibits impedance values of ~2.4–2.9 kΩ between electrode needles at 1 kHz, closely matching in vivo measurements (~2 kΩ) obtained in Sus scrofa domesticus nerve tissue. Its structural and electrical fidelity enables systematic evaluation of electrode–nerve contact properties, signal transmission, and insertion behavior under controlled conditions, while reducing reliance on animal experiments. This bio-inspired simulator offers a scalable and physiologically relevant testbed that bridges materials engineering and translational neuroprosthetics, accelerating the development of next-generation implantable neural interfaces. Full article

Background/Objectives: This article brings forward a novel methodology for the intra-op approach of forearm amputation stumps to facilitate their subsequent wireless connection to a neural prosthesis. A neural prosthesis offers the amputee more motor functions compared to myoelectric prostheses, but the neural prosthesis must be connected to the patient’s stump nerves. Methods: An experimental animal study was conducted on 15 Wistar rats. Under anesthesia, the sciatic nerve was carefully dissected and preserved using a folding technique to maintain maximum length without tension. Nerves were repositioned with consideration for future use with biocompatible conduits. Morphometric measurements (nerve length, external diameter, fascicle count) were performed, followed by statistical analysis of length–diameter correlations. Results: The techniques show that the length of the nerves in the amputation stump can be preserved and integrated into the muscle masses with appropriate methods and biomaterials, which ensures the transmission of motor impulses to control the movements of a prosthesis. Fibrosis and mechanical injury have a lower risk of occurring with the nerves protected in the muscle mass. Through statistical analysis we find that sciatic nerve length and diameter have a positive correlation (r = 0.71, p = 0.003), supporting anatomic plausibility for human extrapolation of results. Conclusions: The amputation technique preserves much of the nerve length and viability and is simple to perform. Neural electrode implantation can be facilitated by folding the nerve within a large muscle mass and using biomaterial conduits. Better rehabilitation of the patient may occur with the use of a prosthesis equipped with more functions and superior control. Full article

Ageing results in the progressive loss of near vision, known as presbyopia, which impacts individuals and society. Existing corrective methods offer only partial compensation and do not restore dynamic focusing at varying distances. This work presents a closed-loop correction system for presbyopia, employing biopotential signals from the ciliary muscle and an artificial neural network to predict the eye’s accommodative state in real time. Non-invasive contact lens electrodes collect biopotential data, which are preprocessed and classified using a multi-layer perceptron. The classifier output guides a control system that adjusts an external focus-tunable lens, enabling both accommodation and disaccommodation similar to a young eye. The system demonstrated an accuracy of 0.79, with F1-scores of 0.78 for prediction of accommodation and 0.77 for disaccommodation. Using the system in two presbyopic subjects, near visual acuity improved from 0.28 and 0.38 to 0.04 and −0.03 logMAR, while distance acuity remained stable. Despite challenges such as signal quality and individual variability, the findings demonstrate the feasibility of restoring near-natural accommodation in presbyopia using neuromuscular signals and adaptive lens control. Future research will focus on system validation, expanding the dataset, and pre-clinical testing in implantable devices. Full article

Iron oxide nanoparticles (IONs) exhibit biocompatibility, ease of drug loading, and potential for generating forces and heat in a magnetic field, enhancing Magnetic Resonance Imaging (MRI). This study proposes coating IONs on electrode surfaces to improve performance and neuron bonding. Methods included synthesizing IONs, grafting chondroitin sulfate (CS), and co-depositing with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). Results showed reduced impedance, increased charge storage, and improved signal quality in vivo. Full article

Silicon carbide (SiC)-coated carbon nanowalls (CNWs) have been proposed for use as implantable scaffold electrodes. Therefore, we investigated the effects of the SiC coating on CNWs and assessed the effects of the application of electrical stimulation (ES) on human mesenchymal stem cells cultured on SiC-coated CNWs. Measurements were conducted using immunofluorescence staining, proliferation assays, and quantitative reverse transcription polymerase chain reaction. Our results showed that the SiC coating increased the cell adhesion area, and the combination of the SiC coating and ES promoted cell proliferation. Furthermore, ES enhanced osteogenic differentiation on CNWs, both with and without the SiC coating. In SiC-coated samples, the increase in wall thickness of CNWs by the SiC coating promoted neural differentiation. These findings indicate that scaffold electrodes composed of SiC-coated CNWs enhance cell adhesion and proliferation; the application of ES to such electrodes promotes osteogenic differentiation, while the SiC coating itself promotes neural differentiation. Full article

Intracortical microelectrode arrays (MEAs) are tools for recording and stimulating neural activity, with potential applications in prosthetic control and treatment of neurological disorders. However, when chronically implanted, the long-term functionality of MEAs is hindered by the foreign body response (FBR), characterized by gliosis, neuronal loss, and the formation of a glial scar encapsulating layer. This response begins immediately after implantation and is exacerbated by factors such as brain micromotion and the mechanical mismatch between stiff electrodes and soft brain tissue, leading to signal degradation. Despite progress in mitigating these issues, the underlying mechanisms of the brain’s response to MEA implantation remain unclear, particularly regarding how cells sense and respond to the associated mechanical forces. Mechanosensitive ion channels, such as the Piezo family, are key mediators of cellular responses to mechanical stimuli. In this study, silicon-based NeuroNexus MEAs consisting of four shanks were implanted in the rat somatosensory cortex for sixteen weeks. Weekly neural recordings were conducted to assess signal quality over time, revealing a decline in active electrode yield and signal amplitude. Immunohistochemical analysis showed an increase in GFAP intensity and decreased neuronal density near the implant site. Furthermore, Piezo1—but not Piezo2—was strongly expressed in GFAP-positive astrocytes within 25 µm of the implant. Piezo2 expression appeared relatively uniform within each brain slice, both in and around the MEA implantation site across cortical layers. Our study builds on previous work by demonstrating a potential role of Piezo1 in the chronic FBR induced by MEA implantation over a 16-week period. Our findings highlight Piezo1 as the primary mechanosensitive channel driving chronic FBR, suggesting it may be a target for improving MEA design and long-term functionality. Full article

Understanding the mechanical behavior of implanted neural electrode arrays is crucial for BCI development, which is the foundation for ensuring surgical safety, implantation precision, and evaluating electrode efficacy and long-term stability. Therefore, a reliable FE models are effective in reducing animal experiments and are essential for a deeper understanding of the mechanics of the implantation process. This study established a novel finite element model to simulate neural electrode implantation into brain tissue, specifically characterizing the nonlinear mechanical responses of brain tissue. Synchronized electrode implantation experiments were conducted using ex vivo porcine brain tissue. The results demonstrate that the model accurately reproduces the dynamics of the electrode implantation process. Quantitative analysis reveals that the implantation force exhibits a positive correlation with insertion depth, the average implantation force per electrode within a multi-electrode array decreases with increasing electrode number, and elevation in electrode size, shank spacing, and insertion speed each contribute to a systematic increase in insertion force. This study provides a reliable simulation tool and in-depth mechanistic analysis for predicting the implantation forces of high-density neural electrode arrays and offer theoretical guidance for optimizing BCI implantation device design. Full article

Implantable electronic devices are driving innovation in modern medical technology and have significantly improved patients’ quality of life. This review comprehensively analyzes the latest technological trends in implantable electronic devices used in major organs, including the heart, brain, and skin. Additionally, it explores the potential for application in the gastrointestinal system, particularly in the field of biliary stents, in which development has been limited. In the cardiac field, wireless pacemakers, subcutaneous implantable cardioverter-defibrillators, and cardiac resynchronization therapy devices have been commercialized, significantly improving survival rates and quality of life of patients with cardiovascular diseases. In the field of brain–neural interfaces, biocompatible flexible electrodes and closed-loop deep brain stimulation have improved treatments of neurological disorders, such as Parkinson’s disease and epilepsy. Skin-implantable devices have revolutionized glucose management in patients with diabetes by integrating continuous glucose monitoring and automated insulin delivery systems. Future development of implantable electronic devices incorporating pressure or pH sensors into biliary stents in the gastrointestinal system may significantly improve the prognosis of patients with bile duct cancer. This review systematically organizes the technological advances and clinical outcomes in each field and provides a comprehensive understanding of implantable electronic devices by suggesting future research directions. Full article

Background/Objectives: Cerebellar cognitive affective syndrome (CCAS) is a well-recognized postoperative complication in children following resection of brain tumors involving cerebellar midline structures. The fastigial nucleus is regarded as relevant, but the underlying neural mechanisms remain incompletely understood. This study uses an oddball paradigm designed to model attentional and learning processes relevant to CCAS to investigate how early-life lesions of the fastigial nucleus in rats affect cognitive performance and neural information processing in the medial prefrontal cortex (mPFC) in adulthood. Methods: Fastigial lesions were induced stereotaxically in 23-day-old male Sprague Dawley rats [n = 9]. Naïve [n = 9] and sham-lesioned rats [n = 6] served as controls. As adults, all rats were trained in an oddball paradigm requiring discrimination of a rare target tone from a rare distractor and a frequent standard tone. Local field potentials (LFPs) were recorded from electrodes implanted in the mPFC during oddball testing and event-related potentials (ERPs) were analyzed. Results: Rats with fastigial lesions required significantly more training days to reach ≥70% correct performance criterion. In fully trained rats, analysis of neural recordings during behavioral testing revealed reduced ERP amplitudes and prolonged latencies of late ERP components after target stimuli. Developmental fastigial lesions lead to lasting deficits in cognitive learning capacity and neural mPFC processing, highlighting the integrative role of cerebellar midline structures in higher-order cognitive function and sensory discrimination. Conclusions: This rodent model provides a valuable translational platform for further investigating the neural basis of CCAS and may inform neurosurgical strategies aimed at minimizing cognitive sequelae in children undergoing cerebellar tumor resection. Full article

Many speech coding strategies have been developed over the years, but comparing them has been convoluted due to the difficulty in disentangling brand-specific and patient-specific factors from strategy-specific factors that contribute to speech understanding. Here, we present a comparison with a ‘virtual’ patient, by comparing two strategies from two different manufacturers, Advanced Combination Encoder (ACE) versus HiResolution Fidelity 120 (F120), running on two different implant systems in a computational model with the same anatomy and neural properties. We fitted both strategies to an expected T-level and C- or M-level based on the spike rate for each electrode contact’s allocated frequency (center electrode frequency) of the respective array. This paper highlights neural and electrical differences due to brand-specific characteristics such as pulse rate/channel, recruitment of adjacent electrodes, and presence of subthreshold pulses or interphase gaps. These differences lead to considerably different recruitment patterns of nerve fibers, while achieving the same total spike rates, i.e., loudness percepts. Also, loudness growth curves differ significantly between brands. The model is able to demonstrate considerable electrical and neural differences in the way loudness growth is achieved in CIs from different manufacturers. Full article

Background/Objectives: The human insula is a key structure implicated in integrating internal states and external food cues, yet its precise role remains unclear, in part due to the temporal limitations of neuroimaging techniques like fMRI. To address this gap, we conducted an exploratory study using an intracranial EEG (iEEG) to investigate how the insula encodes both the subjective and objective properties of food-related stimuli, and how this encoding is modulated by hunger and satiety. Methods: Eight patients with drug-resistant epilepsy undergoing a pre-surgical evaluation between 2017 and 2023 participated in this study. Depth electrodes implanted in the insular cortex recorded event-related potentials (ERPs) in response to visual food cues. The sessions were conducted in two prandial states (hungry and satiated). The subjective ratings (appetite and palatability) and objective nutritional values (e.g., calories, carbohydrates) were collected and analyzed using paired t-tests, MANOVAs, and partial correlations. Results: Hunger increased the ERP amplitudes within the 350–450 ms interval, consistent with the EPIC model and positive alliesthesia, while satiety unexpectedly enhanced the early responses (150–250 ms). Importantly, the neural activity related to nutritional values was largely uncorrelated with the subjective ratings, suggestive of distinct processing streams. The mid- and posterior insula showed greater sensitivity to both subjective and nutritional information than the anterior insula. Conclusions: These findings offer novel electrophysiological insights into how the insula differentiates between implicit and explicit food-related signals, depending on the homeostatic state. This work supports a dual-route model of food cue processing, and may inform interventions targeting insular activity in disordered eating. Full article

Epilepsy is a neurological disorder characterized by recurrent, unprovoked seizures, affecting millions worldwide. While anti-seizure medications serve as first-line treatment, approximately one-third of patients develop drug-resistant epilepsy (DRE), necessitating alternative interventions. Deep brain stimulation (DBS) has emerged as a promising therapy for DRE, particularly for patients who are ineligible for resective surgery. DBS involves stereotactic implantation of electrodes into target brain regions, such as the anterior nucleus of the thalamus (ANT), centromedian nucleus (CMT), and hippocampus (HC), to modulate aberrant neural activity and to reduce seizure frequency. Anesthesia plays a critical role in DBS implantation, influencing both patient safety and procedural success. The choice of anesthetic technique must balance patient comfort with the preservation of neurophysiological signals used for intraoperative electrode localization. A well-chosen anesthetic strategy can enhance the efficacy of electrode placement by minimizing patient movement and preserving critical neurophysiological signals for real-time monitoring. This precise targeting enhances safety via a reduction in perioperative risks and an improvement in long-term seizure control. Anesthetic considerations in epilepsy patients differ from those in movement disorders due to variations in their nuclei targets during DBS. Despite the increasing use of DBS for epilepsy following its FDA approval in 2018, research on anesthetic effects specific to this population remains limited. This narrative review, therefore, examines anesthetic approaches, pharmacological implications, potential complications, and evolving methods for DBS implantation in epilepsy patients, highlighting new insights and unique considerations in this population. Understanding these factors is essential for optimizing surgical outcomes and improving the safety and efficacy of DBS in epilepsy treatment. Full article

Background/Objectives: Intracranial macroelectrode implantation is a pivotal clinical tool in the evaluation of drug-resistant epilepsy, allowing further insights into the localization of the epileptogenic zone and the delineation of eloquent cortical regions through cortical stimulation. Additionally, it provides an avenue to study brain functions by analyzing cerebral responses during neuropsychological paradigms. By combining macroelectrodes with microelectrodes, which allow recording the activity of individual neurons or smaller neural clusters, recordings could provide deeper insights into neuronal microcircuits and the brain’s transitions in epilepsy and contribute to a better understanding of neuropsychological functions. In this study, one or two hybrid macro-micro electrodes were implanted in the anterior-inferior insular region in patients with refractory epilepsy. We report our experience and share some preliminary results; we also provide some recommendations regarding the implantation procedure for hybrid electrodes in the insular cortex. Methods: Stereoelectroencephalography was performed in 13 patients, with one or two hybrid macro-microelectrodes positioned in the insular region in each patient. Research neuropsychological paradigms could not be implemented in two patients for clinical reasons. In total, 23 hybrid macro-microelectrodes with eight microcontacts each were implanted, of which 20 were recorded. Spiking activity was detected and assessed using WaveClus3. Results: No spiking neural activity was detected in the microcontacts of the first seven patients. After iterative refinement during this process, successful recordings were obtained from 13 microcontacts in the anterior-inferior insula in the last four patients (13/64, 20.3%). Hybrid electrode implantation was uneventful with no complications. Obstacles included the absence of spiking activity signals, unsuccessful microwire dispersion, and the interference of environmental electrical noise in recordings. Conclusions: Human microelectrode recording presents a complex array of challenges; however, it holds the potential to facilitate a more comprehensive understanding of individual neuronal attributes and their specific stimulus responses. Full article

Cytomegalovirus (CMV) infection in pregnant women is one of the most common causes of congenital infection in children. It is often asymptomatic but can lead to serious complications, including progressive sensorineural hearing loss. Profound hearing loss is an indication for cochlear implantation (CI). Electrode impedance and neural response telemetry (NRT) thresholds can be measured to confirm correct electrode placement and speech processor programming. Background/Objectives: The aim of the study is to evaluate the hearing outcome of children with profound sensorineural hearing loss or deafness due to cCMV infection after CI compared to a control group of children born with other causes of congenital hearing loss and to identify prognostic factors predicting the outcome of patients with hearing loss due to cCMV infection after CI. Methods: A retrospective study was conducted in patients implanted between 2016 and 2023 at the Department of Otolaryngology of the Institute of the Polish Mother’s Memorial Hospital Research Institute in Łódź. Pre- and postoperative hearing levels, electrode impedance and neural response telemetry (NRT) thresholds were compared. The degree of pre-implantation hearing loss was assessed by the level of the recorded V-wave in the ABR test. Post-implantation hearing assessment was based on the last available free-field tonal audiometry measurement. Impedance measurements were included: intraoperative, 1, 6, 12 months after CI, respectively, and NRT thresholds. Results: The final analysis included 84 patients with profound sensorineural hearing loss and complete audiological follow-up data: 13 patients with congenital CMV (cCMV) infection and 71 patients with other causes of deafnes. The analysis included 175 implanted ears: 17 in the CMV group and 158 in the control group. The age at implantation ranged from 1 to 11 years in the CMV and from 1 to 13 years in the control group. Mean preoperative hearing thresholds were 94.54 dB in the CMV group and 97.04 dB in the control group. At the most recent postoperative evaluation, mean thresholds improved to 33.83 dB and 36.42 dB, respectively. No statistically significant differences were observed between the groups. Mean intraoperative NRT values were 79.74 in the CMV group and 86.90 in the non-CMV group. Final NRT values were 129.77 and 130.76, respectively. Mean impedance values measured intraoperatively and at 1, 6 and 12 months postoperatively were 11.09 kOhm, 13.40 kOhm, 8.35 kOhm and 8.25 kOhm in the CMV group; and 12.28 kOhm, 14.06 kOhm, 9.60 kOhm and 8.00 kOhm in the control group, respectively. Conclusions: CI in children with deafness caused by cCMV infection is an effective treatment option. Initial electrical impedance values of the electrodes increase after implant activation and decrease in subsequent months of follow-up, suggesting the absence of active adhesion processes in the cochlea. Full article

Understanding brain function requires advanced neural probes to monitor electrical and chemical signaling across multiple timescales and brain regions. Microelectrode arrays (MEAs) are widely used to record neurophysiological activity across various depths and brain regions, providing single-unit resolution for extended periods. Recent advancements in flexible MEAs, built on micrometer-thick polymer substrates, have improved integration with brain tissue by mimicking the brain’s soft nature, reducing mechanical trauma and inflammation. These flexible, subcellular-scale MEAs can record stable neural signals for months, making them ideal for long-term studies. In addition to electrical recording, MEAs have been functionalized for electrochemical neurotransmitter detection. Electroactive neurotransmitters, such as dopamine, serotonin, and adenosine, can be directly measured via electrochemical methods, particularly on carbon-based surfaces. For non-electroactive neurotransmitters like acetylcholine, glutamate, and γ-aminobutyric acid, alternative strategies, such as enzyme immobilization and aptamer-based recognition, are employed to generate electrochemical signals. This review highlights recent developments in flexible MEA fabrication and functionalization to achieve both electrochemical and electrophysiological recordings, minimizing sensor fowling and brain damage when implanted long-term. It covers multi-time scale neurotransmitter detection, development of conducting polymer and nanomaterial composite coatings to enhance sensitivity, incorporation of enzyme and aptamer-based recognition methods, and the integration of carbon electrodes on flexible MEAs. Finally, it summarizes strategies to acquire electrochemical and electrophysiological measurements from the same device. Full article