PURPOSE: The objective detection of local visual field defects using multi-focal pattern visual evoked potentials (VEP) has recently been described. The individual waveforms show variable polarity in different parts of the visual field due to underlying cortical convolutions. Normal trace arrays were examined to determine if certain areas of similar ...

This study was designed to evaluate the pathophysiological response of the cochlea following long-term intracochlear electrical stimulation using a poorly charge-balanced stimulus regime, leading to direct current (DC) levels >0.1 microA. Four normal-hearing adult cats were bilaterally implanted with scala tympani electrode arrays and unilaterally stimulated for periods up to ...

Urethane is a standard anesthetic utilized for in vivo recordings in the hippocampus. In studies of long-term potentiation (LTP), the measure of interest is the response amplitude minutes to hours following train delivery. In the absence of experimental treatment, we have consistently observed upward drift in the amplitude of the ...

In order to improve the technique of transoesophageal atrial stimulation (TAS), the effects of body position, interelectrode spacing and electrode surface area on pacing threshold were assessed in two substudies. The effects of intra-oesophageal local anaesthesia and of two different pacing wave configurations on pacing threshold and discomfort were also ...

A common approach to test the time-response of carbon fibre microelectrodes entails the use of a flow injection system which allows delivery of a bolus of test compound in the flow stream to a detector electrode. The introduced bolus is distorted from its original form by convective and dispersive forces ...

We report on a multichannel liquid-crystal-based wave-front corrector with smooth modal influence functions. The phase is controlled by application of spatially localized ac voltages to a distributed voltage divider formed by a liquid-crystal layer sandwiched between a high-conductance and a low-conductance electrode. The shape of the influence function depends on ...

Excised antennae have been used to record aphid electroantennograms (EAGs) but these preparations have small, rapidly declining responses and a short usable life. An improved EAG technique is described and evaluated using alate virginoparae of the black bean aphid, Aphis fabae, and a series of plant volatiles. EAG recording with ...

Muscular action potential conduction velocity (CV) and mean power frequency (MPF) are commonly used parameters to describe the surface electromyographic signal (SEMG). The discrepancies concerning the behavior and interpretation of these main parameters in the literature have motivated this work. Our objective was to evaluate within- and between-individual reproducibility, sensitivity ...

Gap detection thresholds were measured as an indication of the amount of interaction between electrodes in a cochlear implant. The hypothesis in this study was as follows: when the two stimuli that bound the gap stimulate the same electrode, and thus the same neural population, the gap detection threshold will ...

An electrostatic haptic display with three 7 x 7 electrode arrays of three different sizes was fabricated on a 4-in wafer using lithographic microfabrication techniques. The display utilizes electrostatic stimulation to generate a tactile sensation of texture on a scanning finger. The tactile sensation appeared to be a result of ...

We examined the attenuation and integration of spontaneous excitatory postsynaptic potentials (sEPSPs) in the dendrites of presumed motoneurons (MNs) of organotypic rat spinal cord cultures. Simultaneous whole cell recordings in current-clamp mode were made from either the soma and a dendrite or from two dendrites. Direct comparison of the two ...

Bipolar intramuscular wire electrodes and spectral analysis of the electromyographic signal have been used to measure fatigue in muscles that cannot be studied with surface electrodes. Intramuscular electrodes can detect a greater range of frequencies from muscle, obtain a less distorted signal, and are therefore felt to be more sensitive ...

Percutaneous microneurography is a powerful technique allowing studies of activity in single nerve fibres of conscious humans. However, the mechanisms by which single-unit recordings are achieved with this technique are not fully understood. To further elucidate these mechanisms, dual-lead recordings, using a modified concentric needle electrode with two separate recording ...

BACKGROUND: The use of a specific electrode type in laryngeal electromyography has not been standardized. Laryngeal electromyography is usually performed with hooked-wire electrodes or concentric needle electrodes. Hooked-wire electrodes have the advantage of allowing laryngeal movement with ease and comfort, whereas the concentric needle electrodes have benefits from a technical ...

A prototype photon-beam-position monitor has been designed, fabricated and tested at the Taiwan Light Source of the Synchrotron Radiation Research Center. Aluminium was chosen as the material of the blade electrodes due to its low atomic number and high thermal conductivity. The resolution of this photon-beam-position monitor was <+/-1 micro ...

BACKGROUND: Electrical mapping studies indicate an interval of 40 to 100 ms between a defibrillation shock and the earliest activation that propagates globally over the ventricles (globally propagated activation, GPA). This study determined whether activation occurs during this interval but propagates only locally before being blocked (locally propagated activation, LPA). ...

Experiments have been performed to characterize the electrical properties and functionality of a poly(3-hexylthiophene)-coated platinum electrode developed as a sensor for immunoassay read-out. Admittance measurements were performed on the coated electrodes as a function of frequency. The admittance spectra obtained show that the sensor is capacitive in nature. A circuit ...

Use of brainstem potentials in audiology is based on identifying a response in the near-threshold range. Wave V has turned out to be the component of the brainstem potentials that can be detected with a great deal of reliability when assessment of the threshold for the particular stimulus is desirable. ...

This study considers the precision and accuracy of bipolar corneal electrodes compared with unipolar intravitreal methods in collecting electroretinographic (ERG) recordings from a small animal. Flash ERGs were obtained from 9 adult guinea pigs on three occasions. Corneal bipolar (Burian-Allen) electrodes were used to collect data on the first two ...

Various methods for detrusor EMG in the living mammal have been described in the literature. These methods do insufficiently take into account signal components that are caused by movement between the electrodes and the bladder wall. Reliable detrusor EMG has not been achieved yet. This study investigates the feasibility of ...

OBJECTIVES: Clinical knowledge about myoelectrical frequency is well known, but the factors responsible for recorded myoelectrical amplitude remain less clear. METHODS: We assembled an electrogastrographic system that could automatically compute the dominant myoelectrical frequency and power and power ratio. We enrolled 50 healthy volunteers (25 men and 25 women) to ...

Several problems arise when electrophysiological measurements are attempted on cells exposed to an electric field. In addition to field distortion produced by the reference electrode, membrane potential measurements by conventional microelectrode or patch-clamp techniques suffer serious interference from the applied field. We describe here a novel method for measurement of ...

We assessed relationships of evoked electrical and light scattering changes from cat dorsal hippocampus following Schaeffer collateral stimulation. Under anesthesia, eight stimulating electrodes were placed in the left hippocampal CA field and an optic probe, coupled to a photodiode or a charge-coupled device camera to detect scattered light changes, was ...

To fully understand the mechanisms of defibrillation, it is critical to know how a given electrical stimulus causes membrane polarizations in cardiac tissue. We have extended the concept of the activating function, originally used to describe neuronal stimulation, to derive a new expression that identifies the sources that drive changes ...

The purpose of this study was to determine whether changes in bioelectrical impedance (BI) can reveal regional extracellular fluid (ECF) alterations. ECF changes were induced by holding various arm positions for ten minutes, and they were evaluated through the measurement of BI in eight normal adult subjects. A low frequency ...

The feasibility of using the spiral nerve cuff electrode design for recordings of respiratory output from the hypoglossal (HG) and phrenic nerves is demonstrated in anesthetized, paralyzed, and artificially ventilated cats. Raw neural discharges of the HG nerve were analyzed in terms of signal-to-noise ratios and frequency spectra. The rectified ...

The compound action potential (CAP) thresholds provide a reliable indicator for cochlear functional integrity during experimentation in birds as well as in mammals. However, if experimental manipulations are necessary in the middle ear/inner ear spaces, the round window electrodes are often inconvenient. In search for an alternative for CAP recordings, ...

The purpose of this study was to assess the capability of magnitude-squared coherence and bicoherence to differentiate monomorphic ventricular tachycardia (MVT) and polymorphic ventricular tachycardia (PVT) in a canine model and to relate these results to the epicardial isochronal maps on a beat-to-beat basis. Unipolar electrograms were simultaneously recorded from ...

Temporal-integration functions and psychometric functions for detection were obtained in eight users of the Nucleus 22-electrode cochlear implant. Stimuli were 100-Hz, 200-microseconds/phase trains of biphasic pulses with durations ranging from 0.44 to 630.4 ms (1 to 64 pulses). Temporal-integration functions were measured for 21 electrodes. Slopes of these functions were ...

The small intestinal basic electrical rhythm (BER) was detected simultaneously with serosal electrodes and a transabdominal superconducting quantum interference device (SQUID) magnetometer in anesthetized rabbits. We induced mesenteric ischemia to correlate serosal electrode recording of changes in BER with the SQUID magnetometer. The BER frequency was obtained by spectral analysis ...

Conduction velocity and recovery of excitability are central facets of reentry arrhythmias, and yet there are no satisfactory techniques for the simultaneous measurement of both from the same area of myocardium. We have developed an electrode arrangement that allows the simultaneous recording of conduction velocity, repolarization of the myocardium together ...

The crural diaphragm electromyogram (EMGdi) is recorded from a sheet of muscle, the fiber direction of which is mostly perpendicular to an esophageal bipolar electrode. The region from which the action potentials are elicited, the electrically active region of the diaphragm (EAR(di)) and the center of this region (EAR(di ctr)) ...

The diaphragm electromyogram (EMGdi) is susceptible to contamination by non-diaphragm related electrical signals such as the ECG, electrode motion artifacts, and other sources of noise. It is difficult to distinguish between these contaminating signals and those that are representative of the non-contaminated EMGdi, especially during periods when the EMGdi amplitude ...

Studies were undertaken to investigate the ability of a user of the Nucleus multi-electrode cochlear implant to judge pitch in the context of musical intervals. The subject had qualified as a musical instrument tuner before he received his implant, and was able to judge the intervals between electrical sensations with ...

In an in vitro study of the sheep's meniscus, the possibilities to reduce the thermal tissue necrosis caused by high-frequency electrosurgery of the meniscus were studied. Under standardized conditions, machine-made sections through the meniscus were cut using electrodes of various thicknesses and different settings of the electric generator. The thermal ...

Pattern electroretinograms are small physiologic signals that require good patient cooperation and long recording times, particularly when conditions are not optimal. Six electrodes were compared to evaluate their efficacy. Pattern electroretinograms were recorded in eight healthy volunteers to high-contrast, pattern-reversal checks (40' width) with Burian-Allen, DTL fiber, C-glide, gold foil, ...

Two groups of rats with bipolar electrodes implanted unilaterally into the left ventral tegmental area were trained to lever-press for the response contingent electrical stimulation. After preliminary lever-press training, two types of daily sessions were held on 10 consecutive days: type T+, current intensity set at the Threshold level and ...

This study arose from the impression that there is a wide variation in the amplitude of the compound sensory nerve action potential (SNAP) when recorded using surface electrodes. Both the physiological factors influencing the SNAP and the method of measurement itself can be viewed as inputs to a system that ...

Gymnotiform electric fish are capable of locating and approaching an electrically discharging conspecific over a range of 1-2 m in a behavior called passive electrolocation. This paper investigates the movements of two species in experiments with approaches to stationary dipoles that are either silenced or jumped to a new direction ...

The electrochemical noise from dry NASICON-based surface electrodes and pregelled Ag-AgCl electrodes is evaluated in saline solutions and on the skin. The electrochemical noise from the electrode/electrolyte interface is found to be negligible (less than 1 microV peak to peak). On the skin, the noise level is highly dependent on ...

The response of cardiac tissue to a stimulus delivered late in the action potential (AP) is important in studies of defibrillation and certain models of ischemia in which reentrant trajectories produce such stimulation. Such stimuli are often strong and delivered in complex spatial arrangements. In this work a two-dimensional computer ...

Traditional multibarreled pipette electrodes are still widely used in microiontophoresis studies. Although better electrodes have been introduced, they are difficult and time-consuming to make. Construction of a carbon fiber recording and microiontophoresis assembly is described here. The construction of a carbon fiber electrode assembly is easy and carbon fibers have ...

The recording characteristics of the monopolar needle in three dimensions have not been well established. A simple spherical recording territory is commonly assumed with the very tip proposed to have a greater spatial recording sensitivity by some authors. We demonstrate by enlarged physical modeling in a homogeneous volume conductor that ...

Cochlear implant users with some residual hearing in the non-implanted ear compared the pitch sensations produced by acoustic pure tones and pulsatile electric stimuli. Pitch comparisons were obtained for pure tones and electrical stimuli presented at different positions (electrodes) in the scala tympani, keeping the electric pulse rate fixed at ...

Many of the molecules involved in biological signaling processes are easily oxidized and have been monitored by electrochemical methods. Temporal response, spatial considerations, and sensitivity of the electrodes must be optimized for the specific biological application. To monitor exocytosis from single cells in culture, constant potential amperometry offers the best ...

The question of how well the temporal structure in pulsatile electrical stimulation is perceived, and the nature of the information that may be conveyed by this temporal structure, is of importance to the further development of speech processing strategies for cochlear implants. The two experiments described here investigated the perception ...

This study demonstrates the impact of the bipolar electrode transfer function on the canine diaphragm electromyogram (EMG) power spectrum, as evaluated with a new electrode design and implantation technique. The results show that: (a) changes in interelectrode distance transformed single-peaked power spectrums into double-peaked spectrums; (b) the mean action potential ...

Simultaneous auditory brainstem responses (ABRs) to click stimuli at 30 and 60 dB nHL were recorded from 16 full term neonates with four electrode arrays: vertical (Cz-Nape of neck), ipsilateral (Cz-Mi), contralateral (Cz-Mc), and horizontal (Mc-Mi). Results indicated that ABR waveforms were morphologically similar to those recorded in adults: Waves ...

Animal electrocorticogram (ECoG) studies have shown that spatial patterns in the gamma band (>20 Hz) reflect perceptual categorization. Spatio-temporal correlations were investigated in the 20-50 Hz range in search for similar phenomena in human ECoG. ECoGs were recorded in a somatosensory discrimination task from 64-electrode subdural grid arrays, with inter-electrode ...

This study, the second of a two-part investigation, assessed changes over time in functional measures of the electrically stimulated auditory system following ototoxic deafening. Guinea pigs were trained to respond behaviorally to threshold level acoustic stimuli and then unilaterally deafened and implanted with a bipolar pair of electrodes within the ...