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At least 19 recordsLinked to original sources
PubMed1976

Electrophysiological recordings in peripheral nerve surgery: a review.

The use of electrophysiological techniques as an adjunct in the surgical repair of peripheral nerve injuries can improve the quality of the repair and thus the degree of functional recovery. These techniques provide objective information needed to assess the degree of injury and can assist the surgeon in making proper decisions regarding treatment of peripheral nerve lesions. The purposes of this paper are to review: (1) the current theories of the functions of peripheral nerves and their and organs, (2) the development of electrophysiological techniques, (3) the principles involved in their use, and (4) the present and possible future applications of these techniques in peripheral nerve surgery and to outline them.

Action Potentials↗
PubMed1977

[A new method for calibration of electrophysiological recording systems (author's transl)].

The method described in this paper permits determination of amplification, band-pass properties, and electrode impedance in electrophysiological experimental setups. The battery powered test-signal generator drives square-wave current pulses through a 2 ohm resistance, which acts as a source of 100 muV p-p pulses. The 2 ohm resistor is wired in series with one of the electrode leads and remains there permanently. For calibration of the above-mentioned properties, one need only turn the generator on, without changing the measurement setup. By observing the shape of the square waves after passing through the system, it is possible to judge the band-pass characteristics of the entire system. Electrode impedance may be measured by putting a (variable) resistor in parallel with the preamplifier input. The test signal current is of the same order of magnitude as currents from biological signal sources. This method makes working with electrophysiological measurement systems which are used in electroretinography, electrooculography, and recording of visually-evoked cortical potentials in ophthalmology much easier.

Amplifiers, Electronic↗
PubMed1979

Electrophysiological recordings from spontaneously contracting reaggregates of cultured smooth muscle cells from guinea pig vas deferens.

Smooth muscle cells were enzymatically dispersed from vasa deferentia of adult male guinea pigs (250-400 g). These cells reassociated in vitro to form monolayers and small spherical reaggregates (0.05-0.3 mm in Diam). Within 48 h of being placed in culture, cells in both types of preparation began to contract spontaneously. The contractions were rhythmic and slow. Cells in the monolayers stopped contracting after approximately 1 wk in vitro, but the reaggregates continued to contract spontaneously for at least 3 wk. Electron microscopy of the reaggregates revealed the presence of thick and thin myofilaments. Overshooting action potentials were recorded in many of the cells penetrated (primarily in reaggregates), and were accompanied by visible contractions of the aggregate or monolayer. Quiescent cells could often be excited by intracellularly applied depolarizing and hyperpolarizing (anodal-break) current pulses. The resting potentials had a mean value of -58 +/- 2 mV. The action potentials were usually preceded by a spontaneous depolarization. The action potentials had slow rates of rise (1--4 V/s) which were unaffected by tetrodotoxin (TTX, 1 microgram/ml), a known blocker of fast Na+ -channels. Verapamil (1 microgram/ml) blocked the action potentials. The mean value of input resistance was 6.9 +/- 0.5 M omega (n = 12). These electrophysiological properties are similar to those of intact adult vas deferens smooth muscle cells. Thus, the cultured adult vas deferens smooth muscle cells retain their functional properties in vitro even after long periods.

Action Potentials↗
PubMed1977

The isolation amplifier, an interface between EEG recorder and data processor.

An isolation amplifier is presented which is intended as an interface between electrophysiological recorders and standard data processing equipment. Due to its floating input and output, differences in ground potentials do not disturb the transmitted signal. Hence, recorder and data processors can be grounded according to the manufacturer's recommendation. Powerline leakage currents are also prevented from loading the ground of the electrophysiological recorder. Compared to the isolation transformer this device saves space, while polarity restorations can be made and no modifications are needed in any piece of equipment.

Amplifiers, Electronic↗
PubMed1977

Cardiac receptors activated during the hypothalamic defence reaction.

The increases of arterial blood pressure, cardiac inotropy and venous return seen during the hypothalamic defence reaction are likely to lead to concomitant excitation of left ventricular receptors with nonmedullated afferents. The integrated efferent pattern of response resulting from the central interaction between the defence reaction and influences from the mentioned cardiac receptors was recently analyzed. These two, essentially opposing influences on the circulation were then seen to interact in such a way as to produce an optimal cardiovascular response with respect to increases in cardiac output and blood supply to the skeletal muscles. However, direct electrophysiological recordings from nonmedullated cardiac efferents during defence area stimulation have hitherto been lacking. The present experiments, performed on chloralose-anesthetized cats and utilizing electrophysiological recordings, clearly demonstrate that the left ventricular receptors are activated by the cardiovascular readjustments induced by the defence reaction. Defence area stimulation increased the activity of these receptors, which work within a very narrow, low frequency range, from 1.1 +/- 0.3 imp/s to 2.7 +/- 0.7 imp/s associated with rises in systolic blood pressure (afterload) and heart rate. Normally such a receptor activation would induce considerable bradycardia and sympathetic inhibition, but particularly the reflex bradycardia is centrally supressed by a concomitant defence area activation. The marked bradycardia often seen immediately upon interruption of the defence area stimulation is, however, probably to a great extent initiated from the excited ventricular receptors.

Animals↗
PubMed1978

Electrophysiological responses in hydranencephaly.

We recorded electrophysiological responses, both electroretinograms (ERGs) and visual evoked responses (VER), at 4 and 21 months of age in a child with hydranencephaly. As expected, the ERG was normal. Despite the apparent absence of most of the cerebral cortex, a VER was present at both visits. The child's visual performance definitely improved both subjectively and electrophysiologically. The VER contained multiple early components in contrast to previous reports, where only a slow, monophasic response was detected.

Anencephaly↗
PubMedDate not supplied

Effects of urethane on hippocampal unit activity in the rat.

The effect of urethane on hippocampal single unit activity in rats paralyzed with gallamine triethiodide was examined to determine possible influences of urethane as an anesthetic for electrophysiological recordings. With intravenous injections of urethane (1.0 g/kg body weight), hippocampal units responded initially with a substantial decrease in spontaneous firing rate. Activity in some cells recovered partially after a period of approximately 45 min. The activity of the remainder of cells recorded remained depressed for periods of time up to 1.5 hr. Longer periods of depression were observed in some cells. The difference in susceptibility to urethane in the population of hippocampal cells may offer a selective alteration in patterns of spontaneous activity in the hippocampus and systems efferent to the hippocampus. A knowledge of such alterations may prove important in interpreting the results of electrophysiological recording in preparations under urethane anesthesia.

Animals↗
PubMed1979

Development of the segmental innervation of the chick forelimb.

A number of recent studies have shown that during embryonic development the initial innervation of a target structure may be made up, in part, by axons which do not form part of the mature innervation of that structure. In the present study we have examined the motor innervation of the major muscles of the chick forelimb at different stages of development using HRP-uptake-labelling of motoneurons, electrophysiological recording and measurement of muscle contraction. In the mature White Leghorn chick the major contribution to the motor innervation of the forelimb is from spinal segments 14, 15 and 16. Using the HRP-labelling technique we have shown that at stages 26-29 of development motoneurons in segments 12-17 have axon terminals in the presumptive biceps muscle. Between stages 30 and 35, however, the axon terminals arising from segments 12, 13, 16 and 17 are lost, leaving the mature innervation from segments 14 and 15. We have also observed the loss of innervation of the biceps muscle by segment 16 using electrophysiological recording of compound action potentials in the biceps nerve and by measurement of the local contraction of the biceps muscle in response to stimulation of the segmental nerves. Similar changes in the innervation of the triceps, extensor metacarpi radialis, flexor carpi ulnaris and flexor digitorum profundus muscles have also been observed. These results are discussed in relation to the hypothesis that (i) the motoneuron pools and muscles in the developing spinal cord and forelimb are matched, (ii) that some axons which arrive in a particular muscle during early development are unable to form a stable connexion and (iii) that the inability of an axon terminal to form a stable connexion in a muscle results in the death of the motoneuron. Intracellular recording from muscle cells at stage 35 shows that the synaptic site on each cell is innervated by about three separate axons. Over the next few stages, however, all but one of the innervating axons is lost. From our contraction studies it is clear that the removal of the excess axon terminals after stage 35 is not associated with the establishment of the mature segmental innervation pattern of the muscle.

Action Potentials↗
PubMed1977

Neuroanatomical aspects of the gerbil inner ear: light microscope observations.

A specialization of the Mongolian gerbil inner ear allows easy access for electrophysiological recording from the auditory nerve and other structures of the internal auditory meatus. The round-window membrane is recessed, creating a cavity connecting the bulla and the external wall of the modiolus. This cavity has been named the round-window antrum. A small opening made in the dorsomedial wall of the round-window antrum gives access directly to the modiolus and internal auditory meatus, with no other openings in the cranium required. This surgery is less drastic than that needed for similar access in most other mammals. The anatomy of the specialized region is presented from studies with the light microscope. Emphasis is placed on the relationship between external features of the wall of the round-window antrum and the internal anatomy of the modiolus and internal auditory meatus. In addition, these studies reveal that cell bodies of the acoustic-nerve nucleus are located in the auditory nerve, central to the glial dome. About 22 +/- 8 cells are found in an auditory nerve. Their appearance with a Nissl stain is similar to cells found in rat, mouse, and man. The cell dendrites are preferentially oriented perpendicular to the longitudinal course of the auditory-nerve fibers. The anatomy of the gerbil auditory system should allow direct electrophysiological recording from these cells.

Animals↗
PubMed1979

Normal short-latency electrophysiological filtered click responses recorded from vertex and external auditory meatus.

We recorded normal electrophysiological responses to third-octave filtered clicks from external auditory meatus (EAM) and vertex electrodes referred to coupled earlobe electrodes (forehead ground). From both vertex and EAM, polarity-sensitive responses predominated at low frequencies and exhibited characteristics of both phase-locked neural responses (frequency-following response or FFR) and cochlear microphonics (CM). The FFR-like response predominated at the vertex site and the CM-like response predominated at EAM. At high frequencies, polarity-insensitive responses closely resembled rectangular-pulse click action potentials and brainstem evoked potentials, with clearly defined N1 and V peaks recorded from EAM and vertex, respectively. As frequency was lowered, the N1 and V peak latencies increased, the peaks broadened, and the latency-intensity curves steepened with greater prolongation occurring at lower click intensities. Lowering click frequency also shortened the N1-V interval and caused the plot of N1-V interval versus click intensity to become steeper. Plots of polarity-insensitive response amplitudes and thresholds against frequency revealed a high frequency bias for both N1 and V, but the V "frequency response" was flatter. A possible explanation of the shortened N1-V interval at low click frequencies based on this flatter V "Frequency response" is presented.

Acoustic Impedance Tests↗
PubMed1979

A microdrive for use with glass or metal microelectrodes in recording from freely-moving rats.

A new subminiature microdrive assembly is described for electrophysiological recording from behaving rats. This very small, lightweight system allows excellent precision in electrode placement and can maintain stable recordings over extended periods. Since the electrode is nonrotating, tissue damage is minimized. Either metal or glass microelectrodes may be used with the system, offering the possibility of iontophoresis for cell marking or neuropharmacological manipulations.

Animals↗
PubMed1979

Effects of brain-stem and thalamic lesions on the corneal reflex: an electrophysiological and anatomical study.

In 9 patients with Wallenberg's lateral medullary syndrome, one patient with a midbrain lesion involving the right side of the tegmentum, and 2 patients with a thalamic lesion, corneal reflexes were investigated by a new electromyographic technique. The electrophysical results were compared with the results obtained by clinical observation. In the lateral medullary lesions the electrophysiologically obtained reflex responses showed four types of abnormality. Type A consisted of a bilateral delay and type B a bilateral absence of the corneal reflex response to stimulation on the affected side in combination with a normal reflex response on both sides when the cornea on the normal side was stimulated. Type C, which was present in one case, and type D which was seen in 3 cases, consisted of a bilateral absence of the corneal reflex upon stimulation on the affected side; stimulation on the unaffected side produced a normal reflex response on the intact side in combination with, respectively, a delay or absence of the corneal reflex response on the affected side. Comparison of the clinical observations with the electrophysiological findings revealed minor discrepancies in type A and B abnormalities. However, the electrophysiological type C and D abnormalities were not detected by clinical observation. These findings demonstrate that electrophysiological recording of the corneal reflex may reveal clinically undetectable abnormalities. From the electrophysiological findings it is concluded that the corneal reflex is conducted along medullary pathways running both ipsilaterally and contralaterally from the stimulated side before connecting, respectively, with the ipsilateral and contralateral facial nucleus. From the anatomical findings it is suggested that the ascending pathways from the spinal fifth nerve complex to the facial nuclei are located in the lateral reticular formation of the lower brain-stem. The normal corneal reflex responses in the presence of thalamic and midbrain lesions involving nociceptive fibres in the trigeminothalamic tract do not support a previously postulated long-loop reflex arc passing through this tract. The suprabulbar influence upon the corneal reflex is discussed.

Brain Diseases↗