Towards a closed loop retinal prosthesis: measuring electrically evoked retinal responses using large electrodes.

Sensory prostheses use arrays of electrodes to stimulate neural tissue and restore a sense of vision or hearing. At perceptible levels of stimulation, the current from each electrode spreads and causes overlapping regions of neural activation. This lack of specificity results in perceptual deficits.

Abdominal Vagus Nerve Stimulation Increases Firing in the Rat Locus Coeruleus.

Background: Cervical vagus nerve stimulation (VNS) is a clinically available treatment for refractory epilepsy and depression. Animal studies show that electrical activation of the noradrenergic brain region, locus coeruleus (LC), is essential for the therapeutic effects of cervical VNS for the treatment of these conditions. Cervical VNS often causes side effects such as coughing, headache, and apnea-hypopnea.

Objective assessment of tinnitus laterality.

Tinnitus is a condition which involves hearing sounds not present externally. This common condition can lead to a range of symptoms, including depression, resulting in a severe impact on quality of life. There are currently no reliable treatments for tinnitus.

Spatially precise activation of the mouse cochlea with a multi-channel hybrid cochlear implant.

Cochlear implants are among the few clinical interventions for people with severe or profound hearing loss. However, current spread during monopolar electrical stimulation results in poor spectral resolution, prompting the exploration of optical stimulation as an alternative approach. Enabled by introducing light-sensitive ion channels into auditory neurons (optogenetics), optical stimulation has been shown to activate a more discrete neural area with minimal overlap between each frequency channel during simultaneous stimulation.

Overcoming failure: improving acceptance and success of implanted neural interfaces.

Implanted neural interfaces are electronic devices that stimulate or record from neurons with the purpose of improving the quality of life of people who suffer from neural injury or disease. Devices have been designed to interact with neurons throughout the body to treat a growing variety of conditions. The development and use of implanted neural interfaces is increasing steadily and has shown great success, with implants lasting for years to decades and improving the health and quality of life of many patient populations.

Graphene-Based Microelectrodes with Reinforced Interfaces and Tunable Porous Structures for Improved Neural Recordings.

Invasive neural electrodes prepared from materials with a miniaturized geometrical size could improve the longevity of implants by reducing the chronic inflammatory response. Graphene-based microfibers with tunable porous structures have a large electrochemical surface area (ESA)/geometrical surface area (GSA) ratio that has been reported to possess low impedance and high charge injection capacity (CIC), yet control of the porous structure remains to be fully investigated. In this study, we introduce wet-spun graphene-based electrodes with pores tuned by sucrose concentrations in the coagulation bath.

Cochlear implant induced changes in cortical networks associated with tinnitus severity.

We investigated tinnitus-related cortical networks in cochlear implant users who experience tinnitus and whose perception of tinnitus changes with use of their implant. Tinnitus, the perception of unwanted sounds which are not present externally, can be a debilitating condition. In individuals with cochlear implants, use of the implant is known to modulate tinnitus, often improving symptoms but worsening them in some cases.

Magnetically Coupled Percutaneous Connector for Chronic Electrical Peripheral Nerve Stimulation and Recording in Awake Rats.

Unlabelled: A fast-growing field of neuroscience and medicine is the treatment of disease via electrical stimulation of the peripheral nervous system. Peripheral nerve stimulation delivers stimulation to nerves of the periphery where the target nerve can and is often located deep within the abdomen. Long-term preclinical animal models that demonstrate the safety and/or efficacy of electrical stimulation have predominantly used a skull mount to connect to neural interfaces.

Gene Electrotransfer via Conductivity-Clamped Electric Field Focusing Pivots Sensori-Motor DNA Therapeutics: "A Spoonful of Sugar Helps the Medicine Go Down".

Viral vectors and lipofection-based gene therapies have dispersion-dependent transduction/transfection profiles that thwart precise targeting. The study describes the development of focused close-field gene electrotransfer (GET) technology, refining spatial control of gene expression. Integration of fluidics for precise delivery of "naked" plasmid deoxyribonucleic acid (DNA) in sucrose carrier within the focused electric field enables negative biasing of near-field conductivity ("conductivity-clamping"-CC), increasing the efficiency of plasma membrane molecular translocation.

Implantation Surgery for Abdominal Vagus Nerve Stimulation and Recording Studies in Awake Rats.

Abdominal vagus nerve stimulation (VNS) can be applied to the subdiaphragmatic branch of the vagus nerve of rats. Due to its anatomical location, it does not have any respiratory and cardiac off-target effects commonly associated with cervical VNS. The lack of respiratory and cardiac off-target effects means that the intensity of stimulation does not need to be lowered to reduce side effects commonly experienced during cervical VNS.

Multimodal assessment of tinnitus using functional near-infrared spectroscopy and psychophysiological measures.

Objective: To use a multimodal approach to classify individuals with tinnitus from controls, and individuals with mild versus severe tinnitus.

Design: We have previously shown feasibility of a non-invasive imaging technique called functional near-infrared spectroscopy (fNIRS) to detect tinnitus-related changes in cortical activity and classify individuals with tinnitus from controls, as well as individuals with mild versus severe tinnitus. In this study we have used a multimodal approach by recording heart rate, heart rate variability and skin conductance, in addition to fNIRS signals, from individuals with tinnitus and controls.

Spread of activation and interaction between channels with multi-channel optogenetic stimulation in the mouse cochlea.

For individuals with severe to profound hearing loss resulting from irreversibly damaged hair cells, cochlear implants can be used to restore hearing by delivering electrical stimulation directly to the spiral ganglion neurons. However, current spread lowers the spatial resolution of neural activation. Since light can be easily confined, optogenetics is a technique that has the potential to improve the precision of neural activation, whereby visible light is used to stimulate neurons that are modified with light-sensitive opsins.

Selective recording of physiologically evoked neural activity in a mixed autonomic nerve using a minimally invasive array.

Real-time closed-loop control of neuromodulation devices requires long-term monitoring of neural activity in the peripheral nervous system. Although many signal extraction methods exist, few are both clinically viable and designed for extracting small signals from fragile peripheral visceral nerves. Here, we report that our minimally invasive recording and analysis technology extracts low to negative signal to noise ratio (SNR) neural activity from a visceral nerve with a high degree of specificity for fiber type and class.

Stimulation parameters for directional vagus nerve stimulation.

Background: Autonomic nerve stimulation is used as a treatment for a growing number of diseases. We have previously demonstrated that application of efferent vagus nerve stimulation (eVNS) has promising glucose lowering effects in a rat model of type 2 diabetes. This paradigm combines high frequency pulsatile stimulation to block nerve activation in the afferent direction with low frequency stimulation to activate the efferent nerve section.

Combined optogenetic and electrical stimulation of the sciatic nerve for selective control of sensory fibers.

Introduction: Electrical stimulation offers a drug-free alternative for the treatment of many neurological conditions, such as chronic pain. However, it is not easy to selectively activate afferent or efferent fibers of mixed nerves, nor their functional subtypes. Optogenetics overcomes these issues by controlling activity selectively in genetically modified fibers, however the reliability of responses to light are poor compared to electrical stimulation and the high intensities of light required present considerable translational challenges.

Auditory nerve responses to combined optogenetic and electrical stimulation in chronically deaf mice.

. Optogenetic stimulation of the auditory nerve offers the ability to overcome the limitations of cochlear implants through spatially precise stimulation, but cannot achieve the temporal precision nor temporal fidelity required for good hearing outcomes. Auditory midbrain recordings have indicated a combined (hybrid) stimulation approach may permit improvements in the temporal precision without sacrificing spatial precision by facilitating electrical activation thresholds.

Abdominal vagus nerve stimulation alleviates collagen-induced arthritis in rats.

Rheumatoid arthritis (RA) is a chronic, autoimmune inflammatory disease. Despite therapeutic advances, a significant proportion of RA patients are resistant to pharmacological treatment. Stimulation of the cervical vagus nerve is a promising alternative bioelectric neuromodulation therapeutic approach.

Effects of an enhanced acoustic environment on residual hearing following chronic cochlear implantation and electrical stimulation in the partially deafened cat.

There is an increasing trend to provide cochlear implants for people with useful residual hearing, typically in the low frequency range (<2 kHz). These recipients typically use both electrical stimulation from their implant and acoustic stimulation that has been amplified with a hearing aid to access their residual hearing, so called electro-acoustic stimulation (EAS). However, a significant problem is the loss of residual hearing following implantation that can occur immediately following surgery or delayed over many months.

Rapid electrophoretic deposition of biocompatible graphene coatings for high-performance recording neural electrodes.

The electrical and biological interfacial properties of invasive electrodes have a significant impact on the performance and longevity of neural recordings in the brain. In this study, we demonstrated rapid electrophoretic deposition and electrochemical reduction of graphene oxide (GO) on metal-based neural electrodes. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and other characterizations confirmed the existence of a uniform and effectively reduced graphene oxide coating.

Animal Models of Hearing Loss after Cochlear Implantation and Electrical Stimulation.

Many hearing-impaired patients may significantly benefit from the Hybrid or electro-acoustic stimulation (EAS) cochlear implant (CI). However, as much as 30-55% of CI recipients lose residual hearing after implantation and the potential for associated benefits of EAS over traditional electric-only stimulation. The cause of this post-implantation hearing loss may be immediate or delayed and result from several factors, including surgical trauma, electric stimulation, and the foreign body response.

Blood glucose modulation and safety of efferent vagus nerve stimulation in a type 2 diabetic rat model.

Vagus nerve stimulation is emerging as a promising treatment for type 2 diabetes. Here, we evaluated the ability of stimulation of the vagus nerve to reduce glycemia in awake, freely moving metabolically compromised rats. A model of type 2 diabetes (n = 10) was induced using a high-fat diet and low doses of streptozotocin.

Effects of chronic implantation and long-term stimulation of a cochlear implant in the partial hearing cat model.

The expansion of criteria for cochlear implantation has resulted in increasing numbers of cochlear implant subjects having some level of residual hearing. The present study examined the effects of implantation surgery and long-term electrical stimulation on residual hearing in a partially deafened cat model. Eighteen animals were partially deafened, implanted and chronically stimulated.

Improving Deep Brain Stimulation Electrode Performance Through Use of Conductive Hydrogel Coatings.

Active implantable neurological devices like deep brain stimulators have been used over the past few decades to treat movement disorders such as those in people with Parkinson's disease and more recently, in psychiatric conditions like obsessive compulsive disorder. Electrode-tissue interfaces that support safe and effective targeting of specific brain regions are critical to success of these devices. Development of directional electrodes that activate smaller volumes of brain tissue requires electrodes to operate safely with higher charge densities.

Computational modelling of nerve stimulation and recording with peripheral visceral neural interfaces.

Neuromodulation of visceral nerves is being intensively studied for treating a wide range of conditions, but effective translation requires increasing the efficacy and predictability of neural interface performance. Here we use computational models of rat visceral nerve to predict how neuroanatomical variability could affect both electrical stimulation and recording with an experimental planar neural interface.We developed a hybrid computational pipeline,sceralervensembleecording andtimulation (ViNERS), to couple finite-element modelling of extracellular electrical fields with biophysical simulations of individual axons.