Most cochlear prostheses use multichannel electrode arrays implanted in the scala tympani to generate multiple parallel channels of activity in the tonotopically mapped auditory nerve. Various materials and geometrical arrangements of contacts and locations within the scala tympani have been used, resulting in substantial differences in the required stimulus strengths ...

BACKGROUND: Although the intensity of neurostimulation (i.e., charge) is a product of current intensity and pulse duration, the effects of the latter on the amplitude of evoked response and subjective discomfort are unknown. Therefore, the authors investigated the effects of current intensity and pulse width, and their interaction with electrode ...

In the Mongolian gerbil, round window (RW) recordings of averaged responses to phase-locked acoustic stimuli which are not alternated in polarity can include both the cochlear mirophonic (CM) and auditory nerve neurophonic (ANN). The ANN can dominate the recordings when the RW electrode is referenced to some portion of the ...

At some synaptic connections in the central nervous system, amplitude distributions of evoked synaptic currents exhibit surprisingly sharp and regularly spaced peaks. At these connections, detailed analysis of the peaks has led to the proposal that the 'quantal' synaptic current displays very little variability, not only at a release site, ...

This study was designed to test the hypothesis that the effects of a strong electrical stimulus on reentrant wavefronts in ventricular fibrillation (VF) are dependent on the timing of the stimulus. We studied six open-chest dogs by computerized mapping techniques. A plaque electrode array with up to 509 bipolar electrodes ...

Technical and instrumentation factors play an important role in obtaining reliable information during electrodiagnostic studies. With contemporary electrodiagnostic equipment, neurophysiologic potentials are detected using a variety of electrodes and undergo differential amplification, filtering, conversion to digital form, and finally, analysis and display. Understanding the signal processing principles, limitations, and sources ...

Behavioral thresholds were measured in four cats by training them to respond behaviorally to acoustic auditory stimuli using food as a reward in an operant reinforcement paradigm. Following training, the subjects were implanted unilaterally with either a scaled-UCSF electrode containing four contacts or an electrode array containing eight intracochlear contacts ...

The distribution of electrical self-stimulation (ESS) foci within the ventral pallidum (VP) was mapped using moveable electrodes in rats. The function relating ESS bar-pressing rate to the frequency of cathodal rectangular pulses (0.4 mA and 0.1 ms) was obtained for several positions of a moveable electrode in the VP and ...

Psychophysical detection threshold vs frequency functions for sinusoidal electrical stimulation of the deafened cochlea were measured in 18 nonhuman primate subjects. Functions for monopolar or widely-spaced ( > 2.5 mm) bipolar stimulation were lower and usually had steeper slopes than those for more narrowly-spaced ( < 2.0 mm) bipolar stimulation. ...

In six healthy subjects, the integrated electromyographic (IEMG) activity of the right masseter muscle was recorded during 10 s of maximum voluntary teeth clenching, without and with manual movements (at a rate of 1.6 Hz, with a force of approximately 3N) of the bipolar surface electrodes affixed to the cheek. ...

An electrical stimulus must create an electric field of approximately 1 V/cm in the extracellular space to stimulate myocardium during diastole. To initiate fibrillation by premature stimulation during the vulnerable period or to defibrillate, an extracellular electric field of approximately 6 V/cm is required, a value approximately six times greater ...

The time of the minimum slope (i.e., the fastest negative deflection) in monopolar (MP) electrograms from normal hearts compares closely with time of phase 0 of the action potential in cells underlying the electrode, but poor rejection of far-field activity may limit the utility of MP electrode technology in dense ...

The site of the recording electrode influences the amplitude of the compound muscle action potential (CMAP) and its variation over a length of nerve. The effects of large electrodes on this source of intraindividual variability were assessed. Right median nerves of 20 healthy subjects were studied, and recordings made at ...

Estimates of electrical auditory brainstem response (EABR) thresholds are compared with behavioral thresholds for electrical stimulation in the same subject using identical stimuli and electrode configurations. Four cats were behaviorally trained to measure acoustic auditory thresholds using food as a reward in an operant reinforcement paradigm. One of the animals ...

Detailed spatial analysis of propagation of individual action potential was performed during spontaneous bursts of activity in the isolated 17-day pregnant rat myometrium. Use was made of high-resolution mapping with simultaneous recordings from 240 extracellular electrodes. Positioning of the electrode assembly by itself did not have any adverse effects, and ...

The reproducibility of transtympanic electrocochleographic components was investigated in normal-hearing subjects and in patients with Menière's disease. The electric responses to short clicks and long tone bursts were studied using repeated stimuli within the same test (intratest), and after replacement of all electrodes (intertest). The parameters of the response to ...

A new technique is presented for extracting the magnitude and direction of ventricular depolarization at the body surface from surface electrocardiographic (ECG) map data. Bipolar electrocardiograms were obtained from 36 sites on the chest surface in five normal subjects. The direction and magnitude of depolarization as seen from the chest ...

A simplified method to manufacture durable, glass-insulated, tungsten microelectrodes with sufficient control of the final electrode impedance is described. This method requires only two instruments, an electrolytic etcher for wires and pipette puller, for manufacturing these electrodes. The manufacture of these electrodes involves 3 steps: (1) etching tungsten wire to ...

Recent data have implicated the size of surface electrodes as an important factor affecting peripheral nerve excitation. Therefore, we studied the effects of electrode size on the basic excitatory responses and on stimulus characteristics. Four different sizes of self-adhesive surface electrodes were applied over the medial and lateral gastrocnemius muscle ...

A dry, tetrapolar electrode array was used to detect the differential impedance signal at the wrists of 11 adult human subjects. Experiments were conducted to determine the importance of potential-sensing electrode spacing to detect each wearer's pulse rate and respiratory rate. The current-injecting electrodes were at the sides of the ...

We investigated the effects of continuous microstimulation in the cats' posteroventral cochlear nucleus, using chronically implanted activated iridium microelectrodes. We examined 51 electrode sites (39 pulsed sites, and 12 unpulsed sites). Seven hours of continuous stimulation at 500 Hz often produced tissue injury near the tips of the pulsed microelectrodes. ...

This paper describes the design, fabrication and testing of a prototype dry surface electrode for EEG signal recording. The new dry electrode has the advantages of no need for skin preparation or conductive paste, potential for reduced sensitivity to motion artifacts and an enhanced signal-to-noise ratio. The electrode's sensing element ...

Electrically evoked compound action potentials (EECAP) were produced by the injection of pulsed sinusoidal current through metal electrodes into the basal turn. Plots of current threshold against frequency closely resembled conventional compound action potentials (CAP) audiograms for frequencies represented apically of the electrode location. EECAPs were masked by sound and ...

The changes in transmembrane potential during a stimulation pulse in the heart are not known. We have used transmembrane potential sensitive dye fluorescence to measure changes in transmembrane potential along fibers in an anisotropic arterially perfused rabbit epicardial layer. Cathodal or anodal extracellular point stimulation produced changes in transmembrane potential ...

A patient who uses the Ineraid cochlear implant, and who has hearing thresholds less than 50 dB HL for frequencies under 500 Hz in his nonimplanted ear, was asked to match the pitch of low-frequency signals presented to his two ears. The patient produced pitch matches, for frequencies of 125, ...

The object of this work was to develop a monitoring device for measuring the volume of urine in the bladder to signal, in advance, the need to urinate and thus help prevent urinary incontinence. A high-frequency electric current of 50 KHz transmitter was applied to a pair of terminals placed ...

Monopolar and concentric reusable and disposable EMG needle electrodes from several manufacturers were studied at various stages of usage. Needle tips were examined and measured microscopically, and needles were tested for spontaneous noise and resistive and capacitative characteristics at four different test signal frequencies. Resistive and capacitative characteristics were found ...

Pulse frequencies that sustain the same % of the maximum self-stimulation rate (equipotent frequencies) are equipreferred by rats because they elicit identical reward signals. However, when two equipotent frequencies are delivered through different electrodes, lack of equipreference can be expected if the resulting neural signals belong to different rewarding processes ...

A recent study found that the gold foil electrode produces large pattern electroretinogram amplitudes, but the test-retest reliability was low. In a three-center study, we observed that 90% of 29 patients who were tested with gold foil electrodes used three times appeared to have markedly lower amplitudes than when tested ...

The aims of this study were to 1) investigate gastric myoelectrical activity in patients with gastroparesis, 2) validate the cutaneous electrogastrogram (EGG) in tracking the frequency change of the gastric slow wave, and 3) investigate the effect of electrical stimulation on gastric myoelectrical activity. Gastric myoelectrical activity was recorded in ...

The Spectral Maxima Sound Processor (SMSP) incorporates a bank of 16 band-pass filters which are assigned to 16 intracochlear electrodes. In each stimulation period 6 electrodes are activated, based on the outputs of the filters with the largest amplitudes. The SMSP has previously been compared with the present MSP(MULTIPEAK) processor ...

Monolayer networks, obtained from murine spinal cord tissue and grown on a matrix of 64 photo-etched, indium-tin oxide (ITO) microelectrodes, can be electrically stimulated through such thin-film recording electrodes. Multichannel coordinated network activity can be evoked and spontaneous network activity can be modified by generation of additional, multichannel bursting. Although ...

Functional neuromuscular stimulation (FNS) has been used in upper extremity neuroprostheses to provide grasp and release for quadriplegic individuals. The goal of this project was to determine the electrode/muscle input/output characteristics with the greatest influence on the grasp output. This was evaluated by simulating the grasp synthesis procedure, using a ...

1. The issue of isochronicity of olivocerebellar fibre conduction time as a basis for synchronizing complex spike activity in cerebellar Purkinje cells has been addressed by latency measurement, multiple-electrode recording and Phaseolus vulgaris leucoagglutinin (PHA-L) tracing of climbing fibres in the adult rat. 2. The conduction time of the olivocerebellar ...

We measured the contractile properties of the first dorsal interosseous muscle by surface electrodes and needle electrodes during submaximal voluntary contraction. Twenty-seven single motor units were recorded from 5 volunteers by surface electrodes, which were confirmed by subsequent needle electrode recordings. Twitch tension ranged from 0.6 to 10.0 g with ...

Although both monopolar and concentric needle electrodes (MNE and CNE) are widely used in clinical EMG examinations, relatively little attention has been paid to the different recording characteristics of these electrodes. We compared motor unit potentials (MUPs) recorded with MNE and CNE and confirmed that larger MUP pick-up fields and ...

PURPOSE: To examine a photoelectric artifact associated with the ERG-jet corneal contact lens electrode (Universe SA, La Chaux-de-Fons, Switzerland). METHODS: An artifact associated with the ERG-jet, gold foil corneal contact lens electrode was reproduced in vitro and in vivo using 50 msec light flashes. In vitro responses were examined using ...

Assessment of the motor unit architecture based on concentric electrode motor unit potentials requires a thorough understanding of the recording characteristics of the concentric EMG electrode. Previous simulation studies have attempted to include the effect of EMG electrodes on the recorded waveforms by uniformly averaging the tissue potential at the ...

This study compares noninvasive vs invasive electrodes for electrocochleography in chinchillas. Summating potential (SP) amplitude, action potential (AP) amplitude, and AP threshold, recorded with five types of noninvasive electrodes, were compared with simultaneous bulla recordings. Noninvasive electrodes included a needle electrode over the bulla, gold Tiptrode (Etymotic Research, Elk Grove ...

It was hypothesized that intracochlear stimulating electrodes oriented toward the modiolus would require a lower stimulus current to elicit a threshold neural response than longitudinal band electrodes. Electrically evoked auditory brain stem responses (EABRs) and electrode impedances were recorded with full-band and oriented half-band scala tympani electrodes in anesthetized, deafened ...

The purpose of this investigation was to develop a reliable method for in vivo mapping of small exogenously applied electrical fields in the mammalian spinal cord. Experiments were performed in vitro to validate the technique in addition to recordings made in vivo on normal and spinal cord injured rats. Sine ...

The ulnar, hypothenar compound muscle action potential often shows a double-peaked configuration in the negative phase component while the median, thenar potential has a simple dome shape. To investigate the origin of these differences we evaluated the activity at the belly and tendon electrode locations by referencing those sites to ...

Head-restrained rats were conditioned to perform a CNV task: to press a lever in response to an imperative auditory stimulus (S2) given 1.5 sec after a warning stimulus (S1) for a drop of jelly food. With an electrode on the surface of the forelimb cortex, (1) sharp wave complexes immediately ...

Histological studies have shown that the Melbourne/Cochlear electrode array lies along the outer wall of the scala tympani and is therefore some distance from the residual VIIIth nerve elements. In order to investigate the influence of electrode position on neural excitation we systematically varied the position of the electrode array ...

Tissue cutting by electrosurgery is often accompanied with stimulation of nerves and muscles, despite the high frequency of the alternating current being applied. The main source of this stimulation is thought to be the generation of low frequency current by the nonlinear sparking process. However, measurement of this low-frequency current, ...

The effect of electrode position on the upper trapezius muscle on the myo-electric signal amplitude was investigated with special reference to arm position and estimate of force output. Previously, a depression of the electromyogram (EMG) signal has been reported midway between the seventh cervical vertebrae (C7) and acromion (Veiersted 1991, ...

A two-lever choice paradigm with concurrent variable interval schedules of reward was used to measure the growth in the subjective magnitude of reward as a function of current, by finding the adjustment in the stimulating current required to offset a given difference in the rates at which two rewards were ...

The danger in utilizing electrocautery during a surgical procedure on a pacemaker patient depends, to a great extent, on the position of the electrodes. We have studied this influence in an experimental model consisting of a plexiglass tank filled with a saline solution. Seven pacemakers were successively attached to an ...

Spike analysis was performed to determine if surface sphenoidal electrodes were suitable substitutes for depth sphenoidal or anterior temporal electrodes in outpatient EEG recordings for the diagnosis of complex partial seizures of anterior temporal origin. Spike measurements consisted of spike detection rate, spike amplitude, and location of maximal amplitude spikes. ...

BACKGROUND: During atrial flutter, double potentials may be recorded at specific sites in the atria. It has been suggested that double potentials represent sequential activations at the center of the reentrant circuit. An alternative hypothesis is that double potentials represent electrical activity in an area of slow conduction. Understanding their ...