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Results for “Neural Conduction”

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At least 937 records · Page 52Linked to original sources
PubMed1980

Inhibitory action of vagal nerve and spinal cord afferents on discharge pattern of bulbar respiratory modulated neurons.

Single vagal nerve stimuli delivered during burst discharge of respiratory modulated neurons entailed lengthening of an interspike interval in 37% of all units tested. Occasionally stimuli delivered to the spinal cord caused lengthening of interspike intervals in respiratory modulated neurons and in other bulbar units the discharge of which was not modulated with respiration. Vagal stimuli often entailed lengthening of the following interspike interval, while the interval during which stimuli were applied remained unaltered; latencies suggested that inhibitory pathways were polysynaptic. In expiratory-inspiratory (EI) and inspiratory (I) neurons, lengthenings of intervals roughly doubled those noted in inspiratory-expiratory (IE) and expiratory (E) units. Lengthening of intervals depended on stimulus incidence within the intervals and was greatest when stimuli were delivered during the late part of the intervals. In EI and I units, lengthening of intervals occurred mainly during the middle part of burst discharge, in IE and E neurons, however, towards the end of the burst. Conditioning of discharge of respiratory modulated neurons could be demonstrated.

Animals↗
PubMed1982

Acquisition of conditioned facial reflexes in the cat: cortical control of different facial movements.

The motor cortex plays a role in determining which of three different facial movements is acquired in Pavlovian conditioning experiments. Three separate facial reflexes can be distinguished by recording electromyographic activity from the orbicularis oculi (eye blink) and levator orii (nose twitch) muscles. One in a pure eye blink; a second is a nose twitch; the third is a compound eye blink and nose twitch. Which of these movements is elicited by a click (conditioned stimulus) following associative conditioning is reflected by the pattern of unit activity elicited by the click at the motor cortex. Activity is enhanced, after conditioning, in those units that project polysynaptically to the specific muscles performing the learned movement. This enhancement of activity is, in turn, relatable to an enhanced electrical excitability of the involved neurons. Analogous changes in the excitability of neurons of the motor cortex to applied currents can be produced by local application of cholinergic agents. Iontophoresis of acetylcholine, aceclidine (a cholinomimetic drug), or intracellularly applied cyclic GMP produces changes in single neuron membrane resistance that increase neuronal excitability. The units of the motor cortex that respond preferentially to these agents and to the click conditioned stimuli with short latencies have been identified as pyramidal cells of layer V. The axons of these neurons form the pyramidal tract, a pathway characterized as serving voluntary movement. It appears that this system supports rapid transmission and processing of auditory-motor information used to perform learned movements adaptively, selectively, and discriminatively.

Animals↗
PubMed1983

[Tumor-induced function disorders of the acoustic nerve and the lower portions of the auditory pathway].

The manyfold features of acoustic neuromas, respectively tumors of the cerebello pontine angle, are tried to explain by pathophysiologic phenomena of the neural conduction. They are the pathologic fatigue of hearing, the disturbed excitability of the acustico facial stapedial reflex, the impaired velocity of nerve conduction, a poor synchronization of conduction as well as the excessively reduced monosyllabic and dichotic discrimination. With respect to the original tissue, localization, size as well as regional spread and growth pressure there result different constellations of symptoms, eventually only marked discretely. However, all 35 tumors of a defined observation period as well could be diagnosed solely by functional hearing tests.

Adult↗
PubMed1983

[Reticular neurons with double axon projections: participation in execution of the reflex startle response in the cat].

Synaptic processes in the bulbar and pontine reticular neurons with mixed ascending descending axon projections were studied on chloralose-anesthetized cats during startle reaction to somatic stimulation (spino-bulbo-spinal reflex). Characteristics of these processes proved to be similar to those reported for genuine reticulospinal neurons. Evidence was obtained that as in case of reticulospinal neurons, about a half of the investigated cells were simultaneously involved in suprasegmental relay of the spino-bulbo-spinal reflexes.

Animals↗
PubMed1983

[Results of static perimetry in subclinical optic neuritis in multiple sclerosis].

Static perimetry of the central visual field was performed using Harms apparatus and Friedmann's analyser in 20 M.S. patients with subclinical optic neuritis at least for one eye. Sub-clinical optic neuritis was defined as delayed or absent pattern reversal visual evoked potentials (VEPs) associated with normal routine ophthalmological examination (visual acuity, optic fundi, colour vision, kinetic perimetry). Results in patients were compared to data obtained in 22 control subjects, matched for age. A highly significant loss of mean retinal sensitivity was observed in the 20 central degrees of the visual field of eyes with abnormal VEPs. Central relative scotomata were disclosed in 18 of the 33 eyes with abnormal VEPs. Static perimetry was found to be abnormal, for at least one eye, in 15 in the 20 M.S. patients. Thus abnormal VEPs in M.S. are often associated to a lowered capacity to detect a stationary stimulus in the central visual field. The Friedmann's visual field analyser allows a quick and reliable evaluation of the loss of retinal sensitivity in M.S. patients.

Adult↗
PubMed1983

[Reception of information by various types of neurons].

The functional dependence of neuronal MP on afferent impulse activity was revealed with the aid of the mathematical model of neuronal integration processes. This dependence enables to regard a neuron as a continuous information reception system. In the system, the mean impulse rates are important rather than the time of appearance of separate APs. This is relevant mostly for the integrative neurons.

Membrane Potentials↗
PubMed1983

BSER abnormalities in a multiple sclerosis patient with normal peripheral hearing acuity.

The measurement of brain stem evoked potentials has proven clinically useful in determining the presence of multiple sclerosis plaques along the auditory areas of the brain stem. Abnormalities in brain stem evoked responses (BSER) have been identified in patients who manifest normal hearing acuity when evaluated via conventional audiometric techniques. The following case presentation illustrates this confounding clinical finding. The patient was a 20-year-old female who had been previously diagnosed as having multiple sclerosis. Within one month after being evaluated by BSER testing, she was struck and killed by lightning. Although she had a detailed history of normal hearing acuity (documented over the last six years), BSER test results yielded significantly abnormal neural conduction times when the left ear was ipsilaterally stimulated. A histopathologic examination of the patient's brain stem verified involvement of the auditory tracts. Thus physical corroboration of the abnormal BSER results was obtained in the presence of normal hearing acuity.

Adult↗
PubMed1983

[Changes in the concentration of extracellular potassium and the slow negative potential in the somatosensory area of the cortex in response to stimulation of the ventroposterolateral nucleus of the thalamus in the cat].

A single electrical stimulus applied to the VPL nucleus with intensity, strong enough to elicit in gyrus sigmoideus posterior slow negativity following the primary response, caused a local increase in [K+]0 reaching 0.2 mM. On the basis of this finding it is supposed that the slow negativity reflects mainly depolarization.

Animals↗