Spatially selective stimulation of the pig vagus nerve to modulate target effect versus side effect.

Electrical stimulation of the cervical vagus nerve using implanted electrodes (VNS) is FDA-approved for the treatment of drug-resistant epilepsy, treatment-resistant depression, and most recently, chronic ischemic stroke rehabilitation. However, VNS is critically limited by the unwanted stimulation of nearby neck muscles-a result of non-specific stimulation activating motor nerve fibers within the vagus. Prior studies suggested that precise placement of small epineural electrodes can modify VNS therapeutic effects, such as cardiac responses.

Fascicles split or merge every ∼560 microns within the human cervical vagus nerve.

Vagus nerve stimulation (VNS) is Food and Drug Administration-approved for epilepsy, depression, and obesity, and stroke rehabilitation; however, the morphological anatomy of the vagus nerve targeted by stimulatation is poorly understood. Here, we used microCT to quantify the fascicular structure and neuroanatomy of human cervical vagus nerves (cVNs).We collected eight mid-cVN specimens from five fixed cadavers (three left nerves, five right nerves).

Visualization of Pig Vagus Nerve "Vagotopy" Using Ultrasound.

Placement of the clinical vagus nerve stimulating cuff is a standard surgical procedure based on anatomical landmarks, with limited patient specificity in terms of fascicular organization or vagal anatomy. As such, the therapeutic effects are generally limited by unwanted side effects of neck muscle contractions, demonstrated by previous studies to result from stimulation of (1) motor fibers near the cuff in the superior laryngeal and (2) motor fibers within the cuff projecting to the recurrent laryngeal. Conventional non-invasive ultrasound, where the transducer is placed on the surface of the skin, has been previously used to visualize the vagus with respect to other landmarks such as the carotid and internal jugular vein.

Conditional Silencing of H-2D Class I Molecule Expression Modulates the Protective and Pathogenic Kinetics of Virus-Antigen-Specific CD8 T Cell Responses during Theiler's Virus Infection.

Theiler's murine encephalomyelitis virus (TMEV) infection of the CNS is cleared in C57BL/6 mice by a CD8 T cell response restricted by the MHC class I molecule H-2D The identity and function of the APC(s) involved in the priming of this T cell response is (are) poorly defined. To address this gap in knowledge, we developed an H-2D LoxP-transgenic mouse system using otherwise MHC class I-deficient C57BL/6 mice, thereby conditionally ablating MHC class I-restricted Ag presentation in targeted APC subpopulations. We observed that CD11c APCs are critical for early priming of CD8 T cells against the immunodominant TMEV peptide VP2 Loss of H-2D on CD11c APCs mitigates the CD8 T cell response, preventing early viral clearance and immunopathology associated with CD8 T cell activity in the CNS.

Sources of off-target effects of vagus nerve stimulation using the helical clinical lead in domestic pigs.

Objective: Clinical data suggest that efficacious vagus nerve stimulation (VNS) is limited by side effects such as cough and dyspnea that have stimulation thresholds lower than those for therapeutic outcomes. VNS side effects are putatively caused by activation of nearby muscles within the neck, via direct muscle activation or activation of nerve fibers innervating those muscles. Our goal was to determine the thresholds at which various VNS-evoked effects occur in the domestic pig—an animal model with vagus anatomy similar to human—using the bipolar helical lead deployed clinically.

Clinically-derived vagus nerve stimulation enhances cerebrospinal fluid penetrance.

Introduction: Vagus nerve stimulation (VNS) is an FDA-approved neuromodulatory treatment used in the clinic today for epilepsy, depression, and cluster headaches. Moreover, evidence in the literature has led to a growing list of possible clinical indications, with several small clinical trials applying VNS to treat conditions ranging from neurodegenerative diseases to arthritis, anxiety disorders, and obesity. Despite the growing list of therapeutic applications, the fundamental mechanisms by which VNS achieves its beneficial effects are poorly understood.

Functional vagotopy in the cervical vagus nerve of the domestic pig: implications for the study of vagus nerve stimulation.

Objective: Given current clinical interest in vagus nerve stimulation (VNS), there are surprisingly few studies characterizing the anatomy of the vagus nerve in large animal models as it pertains to on-and off-target engagement of local fibers. We sought to address this gap by evaluating vagal anatomy in the pig, whose vagus nerve organization and size approximates the human vagus nerve.

Approach: Here we combined microdissection, histology, and immunohistochemistry to provide data on key features across the cervical vagus nerve in a swine model, and compare our results to other animal models (mouse, rat, dog, non-human primate) and humans.

An Injectable Neural Stimulation Electrode Made from an In-Body Curing Polymer/Metal Composite.

Implanted neural stimulation and recording devices hold vast potential to treat a variety of neurological conditions, but the invasiveness, complexity, and cost of the implantation procedure greatly reduce access to an otherwise promising therapeutic approach. To address this need, a novel electrode that begins as an uncured, flowable prepolymer that can be injected around a neuroanatomical target to minimize surgical manipulation is developed. Referred to as the Injectrode, the electrode conforms to target structures forming an electrically conductive interface which is orders of magnitude less stiff than conventional neuromodulation electrodes.

Design Choices for Next-Generation Neurotechnology Can Impact Motion Artifact in Electrophysiological and Fast-Scan Cyclic Voltammetry Measurements.

Implantable devices to measure neurochemical or electrical activity from the brain are mainstays of neuroscience research and have become increasingly utilized as enabling components of clinical therapies. In order to increase the number of recording channels on these devices while minimizing the immune response, flexible electrodes under 10 µm in diameter have been proposed as ideal next-generation neural interfaces. However, the representation of motion artifact during neurochemical or electrophysiological recordings using ultra-small, flexible electrodes remains unexplored.

Brain structure and cognition 3 years after the end of an early menopausal hormone therapy trial.

Objective: The effects of 2 frequently used formulations of menopausal hormone therapy (mHT) on brain structure and cognition were investigated 3 years after the end of a randomized, placebo-controlled trial in recently menopausal women with good cardiovascular health.

Methods: Participants (aged 42-56 years; 5-36 months past menopause) were randomized to one of the following: 0.45 mg/d oral conjugated equine estrogen (oCEE); 50 μg/d transdermal 17β-estradiol (tE2); or placebo pills and patch for 4 years.

Functional Circuitry Effect of Ventral Tegmental Area Deep Brain Stimulation: Imaging and Neurochemical Evidence of Mesocortical and Mesolimbic Pathway Modulation.

The ventral tegmental area (VTA), containing mesolimbic and mesocortical dopaminergic neurons, is implicated in processes involving reward, addiction, reinforcement, and learning, which are associated with a variety of neuropsychiatric disorders. Electrical stimulation of the VTA or the medial forebrain bundle and its projection target the nucleus accumbens (NAc) is reported to improve depressive symptoms in patients affected by severe, treatment-resistant major depressive disorder (MDD) and depressive-like symptoms in animal models of depression. Here we sought to determine the neuromodulatory effects of VTA deep brain stimulation (DBS) in a normal large animal model (swine) by combining neurochemical measurements with functional magnetic resonance imaging (fMRI).

Dopamine Release in the Nonhuman Primate Caudate and Putamen Depends upon Site of Stimulation in the Subthalamic Nucleus.

Unlabelled: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an effective treatment for medically refractory Parkinson's disease. Although DBS has recognized clinical utility, its biologic mechanisms are not fully understood, and whether dopamine release is a potential factor in those mechanisms is in dispute. We tested the hypothesis that STN DBS-evoked dopamine release depends on the precise location of the stimulation site in the STN and the site of recording in the caudate and putamen.

A Diamond-Based Electrode for Detection of Neurochemicals in the Human Brain.

Deep brain stimulation (DBS), a surgical technique to treat certain neurologic and psychiatric conditions, relies on pre-determined stimulation parameters in an open-loop configuration. The major advancement in DBS devices is a closed-loop system that uses neurophysiologic feedback to dynamically adjust stimulation frequency and amplitude. Stimulation-driven neurochemical release can be measured by fast-scan cyclic voltammetry (FSCV), but existing FSCV electrodes rely on carbon fiber, which degrades quickly during use and is therefore unsuitable for chronic neurochemical recording.

Fornix deep brain stimulation circuit effect is dependent on major excitatory transmission via the nucleus accumbens.

Introduction: Deep brain stimulation (DBS) is a circuit-based treatment shown to relieve symptoms from multiple neurologic and neuropsychiatric disorders. In order to treat the memory deficit associated with Alzheimer's disease (AD), several clinical trials have tested the efficacy of DBS near the fornix. Early results from these studies indicated that patients who received fornix DBS experienced an improvement in memory and quality of life, yet the mechanisms behind this effect remain controversial.