Evaluation of Activated Carbon and Platinum Black as High-Capacitance Materials for Platinum Electrodes.

The application of direct current (DC) produces a rapid and reversible nerve conduction block. However, prolonged injection of charge through a smooth platinum electrode has been found to cause damage to nervous tissue. This damage can be mitigated by incorporating high-capacitance materials (HCM) (e.

A Carbon Slurry Separated Interface Nerve Electrode for Electrical Block of Nerve Conduction.

Direct current (DC) nerve block has been shown to provide a complete block of nerve conduction without unwanted neural firing. Previous work shows that high capacitance electrodes can be used to safely deliver a DC block. Another way of delivering DC safely is through a separated interface nerve electrode (SINE), such that any reactive species that are generated by the passage of DC are contained in a vessel away from the nerve.

Measurement of block thresholds in kiloHertz frequency alternating current peripheral nerve block.

Background: Kilohertz frequency alternating currents (KHFAC) produce rapid nerve conduction block of mammalian peripheral nerve and have potential clinical applications in reducing peripheral nerve hyperactivity. The experimental investigation of KHFAC nerve block requires a robust output measure and this has proven to be the block threshold (BT), the lowest current or voltage at which the axons of interest are completely blocked. All significant literature in KHFAC nerve block, both simulations and experimental, were reviewed to determine the block threshold method that was used.

Activation of the sciatic nerve evoked during epidural spinal cord stimulation in rodents.

Aim: To validate the use of motor activation thresholds (MoT) to titrate stimulation amplitudes for spinal cord stimulation in rodent models.

Methods: We recorded thresholds for MoT and sciatic compound action potentials in ten Sprague-Dawley rats implanted with epidural electrodes. Strength duration curves were fitted to the threshold values.

Electron transfer processes occurring on platinum neural stimulating electrodes: pulsing experiments for cathodic-first, charge-imbalanced, biphasic pulses for 0.566 ⩽ k ⩽ 2.3 in rat subcutaneous tissues.

Objective: Charge injection through platinum neural stimulation electrodes is often constrained by the Shannon limit (Shannon 1992 IEEE Trans. Biomed. Eng.

Reversible conduction block in peripheral nerve using electrical waveforms.

Introduction: Electrical nerve block uses electrical waveforms to block action potential propagation.

Materials & Methods: Two key features that distinguish electrical nerve block from other nonelectrical means of nerve block: block occurs instantly, typically within 1 s; and block is fully and rapidly reversible (within seconds).

Results: Approaches for achieving electrical nerve block are reviewed, including kilohertz frequency alternating current and charge-balanced polarizing current.

Temporary persistence of conduction block after prolonged kilohertz frequency alternating current on rat sciatic nerve.

Objective: Application of kilohertz frequency alternating current (KHFAC) waveforms can result in nerve conduction block that is induced in less than a second. Conduction recovers within seconds when KHFAC is applied for about 5-10 min. This study investigated the effect of repeated and prolonged application of KHFAC on rat sciatic nerve with bipolar platinum electrodes.

Block of motor nerve conduction via transcutaneous application of direct current.

Aims: Nerve conduction block using implanted electrodes is being used increasingly for clinical applications. Alternatively, non-invasive electrical nerve block would be beneficial for applications including pain block and muscle spasticity. Here we developed a novel means of non-invasive electrical nerve conduction blockade - transcutaneous direct current block (tDCB) - that produces direct block of nerve conduction.

Electron transfer processes occurring on platinum neural stimulating electrodes: pulsing experiments for cathodic-first, charge-balanced, biphasic pulses for 0.566 ⩽ k ⩽ 2.3 in rat subcutaneous tissues.

Objective: Our mission is twofold: (1) find a way to safely inject more charge through platinum electrodes than the Shannon limit (k  =  1.75) permits and (2) nurture an interest in the neural stimulation community to understand the electron transfer process occurring on neural stimulating electrodes.

Approach: We report here on measurements of the electrode potential, performed on platinum neural stimulating electrodes in the subcutaneous space of an anesthetized rat under neural stimulation conditions.

Electron transfer processes occurring on platinum neural stimulating electrodes: a tutorial on the i(V e) profile.

The aim of this tutorial is to encourage members of the neuroprosthesis community to incorporate electron transfer processes into their thinking and provide them with the tools to do so when they design and work with neurostimulating devices. The focus of this article is on platinum because it is the most used electrode metal for devices in commercial use. The i(V e) profile or cyclic voltammogram contains information about electron transfer processes that can occur when the electrode-electrolyte interface, V e, is at a specific potential, and assumed to be near steady-state conditions.

Continuous Direct Current Nerve Block Using Multi Contact High Capacitance Electrodes.

Charge-balanced direct current (CBDC) nerve block can be used to block nerve conduction in peripheral nerves. Previous work demonstrated that the CBDC waveform could be used to achieve a 10% duty cycle of block to non-block repeatedly for at least two hours. We demonstrate that the duty cycle of this approach can be significantly increased by utilizing multiple electrode contacts and cycling the CBDC waveform between each contact in a "carousel" configuration.

Characterization of high capacitance electrodes for the application of direct current electrical nerve block.

Direct current (DC) can briefly produce a reversible nerve conduction block in acute experiments. However, irreversible reactions at the electrode-tissue interface have prevented its use in both acute and chronic settings. A high capacitance material (platinum black) using a charge-balanced waveform was evaluated to determine whether brief DC block (13 s) could be achieved repeatedly (>100 cycles) without causing acute irreversible reduction in nerve conduction.

Alternating current and infrared produce an onset-free reversible nerve block.

Nerve block can eliminate spasms and chronic pain. Kilohertz frequency alternating current (KHFAC) produces a safe and reversible nerve block. However, KHFAC-induced nerve block is associated with an undesirable onset response.

Combined KHFAC + DC nerve block without onset or reduced nerve conductivity after block.

Objective: Kilohertz frequency alternating current (KHFAC) waveforms have been shown to provide peripheral nerve conductivity block in many acute and chronic animal models. KHFAC nerve block could be used to address multiple disorders caused by neural over-activity, including blocking pain and spasticity. However, one drawback of KHFAC block is a transient activation of nerve fibers during the initiation of the nerve block, called the onset response.

Direct current contamination of kilohertz frequency alternating current waveforms.

Kilohertz frequency alternating current (KHFAC) waveforms are being evaluated in a variety of physiological settings because of their potential to modulate neural activity uniquely when compared to frequencies in the sub-kilohertz range. However, the use of waveforms in this frequency range presents some unique challenges regarding the generator output. In this study we explored the possibility of undesirable contamination of the KHFAC waveforms by direct current (DC).

Does patterned afferent stimulation of sacral dermatomes suppress urethral sphincter reflexes in individuals with spinal cord injury?

Aims: Dyssynergic contractions of the external urethral sphincter prevent efficient bladder voiding and lead to numerous health concerns. Patterned electrical stimulation of the sacral dermatomes reduces urethral sphincter spasms and allows functional bladder emptying in cats after chronic SCI. Reflex suppression in animals is strongly dependent on stimulus location and pattern.

A Novel Waveform for No-Onset Nerve Block Combining Direct Current and Kilohertz Frequency Alternating Current.

Kilohertz frequency alternating current (KHFAC) has been shown to produce a fast acting, reversible nerve block. The principal drawback to this technique is a short, but intense burst of firing at the initiation of the KHFAC which is referred to as the "onset response". The "onset response" can be eliminated by the use of a second electrode which delivers direct current (DC) briefly during the onset duration.

Different clinical electrodes achieve similar electrical nerve conduction block.

Objective: We aim to evaluate the suitability of four electrodes previously used in clinical experiments for peripheral nerve electrical block applications.

Approach: We evaluated peripheral nerve electrical block using three such clinical nerve cuff electrodes (the Huntington helix, the Case self-sizing Spiral and the flat interface nerve electrode) and one clinical intramuscular electrode (the Memberg electrode) in five cats. Amplitude thresholds for the block using 12 or 25 kHz voltage-controlled stimulation, onset response, and stimulation thresholds before and after block testing were determined.

Electrical stimulation of sacral dermatomes can suppress aberrant urethral reflexes in felines with chronic spinal cord injury.

Aims: Uncoordinated reflex contractions of the external urethral sphincter (EUS) are a major component of voiding dysfunction after neurologic injury. Patterned stimulation of sacral afferent pathways can reduce abnormal EUS reflexes after acute spinal cord injury (SCI); however, effectiveness following chronic SCI is unknown.

Methods: Four adult male cats were implanted with bilateral extradural sacral root electrodes to allow bladder activation and underwent subsequent spinal transection (T10-12).

High frequency sacral root nerve block allows bladder voiding.

Aims: Dyssynergic reflexive external urethral sphincter (EUS) activity following spinal cord injury can prevent bladder voiding, resulting in significant medical complications. Irreversible sphincterotomies or neurotomies can prevent EUS activation and allow bladder voiding, but may cause incontinence or loss of sacral reflexes. We investigated whether kilohertz frequency (KF) electrical conduction block of the sacral roots could prevent EUS activation and allow bladder voiding.

Design, fabrication and evaluation of a conforming circumpolar peripheral nerve cuff electrode for acute experimental use.

Nerve cuff electrodes are a principle tool of basic and applied electro-neurophysiology studies and are championed for their ability to achieve good nerve recruitment with low thresholds. We describe the design and method of fabrication for a novel circumpolar peripheral nerve electrode for acute experimental use. This cylindrical cuff-style electrode provides approximately 270° of radial electrode contact with a nerve for each of an arbitrary number of contacts, has a profile that allows for simple placement and removal in an acute nerve preparation, and is designed for adjustment of the cylindrical diameter to ensure a close fit on the nerve.

Frequency- and amplitude-transitioned waveforms mitigate the onset response in high-frequency nerve block.

High-frequency alternating currents (HFAC) have proven to be a reversible and rapid method of blocking peripheral nerve conduction, holding promise for treatment of disorders associated with undesirable neuronal activity. The delivery of HFAC is characterized by a transient period of neural firing at its inception, termed the 'onset response'. The onset response is minimized for higher frequencies and higher amplitudes, but requires larger currents.

Bursting stimulation of proximal urethral afferents improves bladder pressures and voiding.

Reflex bladder excitation has been evoked via pudendal nerve, pudendal nerve branch and intraurethral stimulation; however, afferent-evoked bladder emptying has been less efficient than direct activation of the bladder via sacral root stimulation. A stimulation method that improves activation of the urethra-bladder excitatory reflex with minimal sphincter recruitment may lead to improved bladder emptying. Fine wire electrodes were placed in the wall of the urethra in five cats.

Suppression of reflex urethral responses by sacral dermatome stimulation in an acute spinalized feline model.

Aims: Reflex contractions of the external urethral sphincter (EUS) are a major component of voiding dysfunction after neurological injury or disease. Aberrant urethral reflexes can prevent voiding and cause serious medical complications. Characterizing these urethral reflexes during genitourinary studies is necessary for evaluating novel pharmacological or neuroprosthetic approaches.

Intraurethral stimulation for reflex bladder activation depends on stimulation pattern and location.

Aims: Reflex bladder excitation has been demonstrated by stimulation of the pudendal nerve and several of its distal branches. However, excitation parameters have not been consistent and the relationship to anatomical locations within the urethra has not been fully investigated. An improved understanding of the lower urinary tract neurophysiology will improve human studies and neuroprosthetic device development.