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Biomedical subjects

R R Marsh

Publications and source records attributed to R R Marsh.

At least 55 records · Page 3Linked to original sources
PubMed1984

Sedation in brainstem response audiometry.

In many children, sedation is virtually essential for reducing myogenic interference during brainstem response (BSR) audiometry. The most widely accepted sedative for young children is chloral hydrate. Children who are tired before the sedation is given fall asleep much more quickly with sedation, and in turn, require fewer doses of chloral hydrate. Instructing the parents to keep the child tired has produced significant increases in percent of those sleeping after the first dose (z = 2.08, P less than 0.05).

Audiometry↗
PubMed1984

Resistance of the auditory brain stem response to high barbiturate levels.

In the comatose patient the auditory brain stem response may be one of the few indices of CNS function available. Because barbiturates may be administered to control intracranial pressure and its sequelae, demonstration of the effect of barbiturates on the brain stem response is desirable. In cats preloaded with 63 mg/kg of pentobarbital, intravenous injection of an additional 60 mg/kg reduced, but did not abolish, the later waves of the response. One cat that survived a cumulative dose of 183 mg/kg continued to show a well-defined brain stem response. Even doses of barbiturate nearly incompatible with survival do not abolish this response.

Animals↗
PubMed1983

Hearing loss induced by viscous fluids in the middle ear.

Dextran solutions of low viscosity (7.5 centipoise) and high viscosity (2.2 poise) were instilled in turn into the middle ears of guinea pigs, using an open bulla preparation. The degree of conductive hearing loss induced was assessed by measurement of the cochlear microphonic. Both solutions produced a comparable degree of hearing loss which was frequency dependent, ranging from 30 dB at 500 Hz to almost zero at 4000 Hz. The results indicate that the degree of conductive hearing loss produced by a serous effusion in otitis media is due solely to an effect on compliance in the middle ear and is independent of the viscosity of the effusion.

Animals↗
PubMed1983

A trial of Biolite ventilation tubes in children: is further use warranted?

A prospective controlled pilot study was undertaken in which Biolite (carbon-coated) ventilation tubes were placed in 44 ears and a conventional silicone tube in the contralateral ear. Long-term follow-up of these patients has revealed little difference in the incidence of tube occlusion or early extrusion. In addition, there were several disadvantages noted with the Biolite tubes: incomplete coating of the tube (especially within the lumen), shedding of the Biolite coating over time, "tattooing" of the tympanic membrane, poor otoscopic visibility, and the higher cost of these tubes. Since the Biolite tube has no documented advantages and, actually, several disadvantages, we believe its use in the treatment of middle ear disorders should be discontinued until significant benefits are demonstrated and present deficiencies are corrected.

Adolescent↗
PubMed1983

Portions of tone pips contributing to frequency-selective auditory brain stem responses.

The portions of tone pips that are effective in increasing the amplitudes of auditory brain stem responses were studied using 6 cats. The responses evoked by pips with identical slopes but different rise times were compared to one another. The results indicated that the effective portion of the tone pips extended more than 4 ms from onset at 500 and 1 000 Hz, and more than 2 ms at 2 000 Hz. Each cycle within these ranges contributed to the increase in response amplitude. These results support the contention that the frequency selectivity of the brain stem response elicited by tone pips is sufficient for objective audiometry.

Acoustic Stimulation↗
PubMed1982

Auditory brain stem responses in infantile spasms.

Auditory brain stem evoked responses (ABRs) and behavioral thresholds were studied in 30 infants with infantile spasms to determine the level of the lesion causing their inattention to sound stimuli. ABR thresholds, peak latencies of waves I and V and the peak interval latency of wave V-I were measured; behavioral audiometric thresholds were determined through conditioned-orientation-reflex (COR) audiometry. Thirty per cent of the infants (9 cases) with infantile spasms showed ABR abnormalities with respect to age-matched controls. The ABR abnormalities were classified into partial disappearance of latter waves (5 cases), prolongation of the wave V-I peak interval (3 cases) and no response (1 case). These findings are clear evidence that brain stem involvement may occur in infantile spasms. Eighty-six per cent of the patients showed threshold elevation by behavioral audiometry which may reflect by cortical dysfunction inherent in psychomotor retardation, as there was no peripheral hearing loss. Our results reveal that brain stem involvement can occur in patients with infantile spasms and their poor responses to sound are due to psychomotor retardation.

Adolescent↗
PubMed1982

Contributing generator of frequency-following response in man.

A contributing generator of the frequency-following response (FFR) was identified in a patient with severe neurological impairment, by comparing latencies and phase shifts of the FFR to the latency of the auditory brainstem evoked responses (ABR), and by comparing the duration of the FFR to that of the acoustic stimulus. In this patient, the ABR comprised only waves I and II; activity in the inferior colliculus was not identified. Both onset and offset latencies and phase shifts of the FFR were substantially shorter than the latency of the first wave of the ABR. The duration of the FFR corresponded precisely to that of the acoustic stimulus. These results are interpreted as supporting the view that the cochlear microphonic potential (CM) contributes to the scalp-recorded FFR.

Brain↗
PubMed1981

A recorder for off-line acquisition of brain stem auditory response data.

A modified cassette tape recorder collects brain stem response data for later off-line analysis. This simple device permits assessments of brain stem function when a signal-averaging computer is not immediately available, and at locations not readily accessible to the computer.

Auditory Perception↗
PubMed1976

Modification of the rat's acoustic startle response by antecedent visual stimulation.

Male hooded and albino rats were exposed to a light flash followed at various temporal intervals by a startle-eliciting 117 db. (re 20 muN/m2) burst of white noise. The visual stimulus engendered startle response inhibition (maximally when the lead time was 64-250 msec) as well as startle response latency reduction (maximally when the lead time was 2-8 msec). The temporal functions for the effects of visual stimuli paralleled those previously reported for startle modification by acoustic events. Further study revealed that, given optimal lead times, inhibition is produced reliably by weaker visual stimuli (3 X 10-6 cd-sec/cm2) than latency reduction (3 X 10-4 cd-sec/cm2). This differential sensitivity to visual stimuli is also analogous to previously reported findings for events in the acoustic environment. It reveals that the neural mechanisms that mediate latency reduction and inhibition can be engaged by either acoustic or visual stimulation.

Acoustic Stimulation↗
PubMed1976

Interaction versus independence of startle-modification processes in the rat.

In a series of experiments it was found that the amount of inhibition produced by a weak acoustic stimulus occurring 64 msec prior to a startle-eliciting stimulus is unaffected by a second weak acoustic stimulus occurring 4 msec prior to the startle-eliciting stimulus. Likewise, the amount of latency reduction produced by an antecedent stimulus with a 4-msec lead time is unaffected by the presence of an antecedent stimulus with a 64-msec lead time. Finally, it was found that both the amount of inhibition produced by a prestimulus with a 64-msec lead time and the amount of latency reduction produced by a prestimulus with a 4-msec lead time are independent of the intensity of the startle-eliciting stimulus. These findings suggest that the inhibition effect is independent of the latency reduction effect and that both are independent of the absolute level of activation in the neural mechanisms responsible for the overt startle response.

Acoustic Stimulation↗
PubMed1976

Modification of the pigeon's visual startle reaction by the sensory environment.

A series of seven experiments related amplitude and latency of the pigeon's startle response, elicited by an intense visual stimulus, to antecedent auditory and visual events in the sensory environment. The data indicated that (a) within broad limits the amplitude of the reflex is a positive function of the intensity of the sensory background prevailing at the time of startle elicitation, (b) a change in the sensory environment occurring 15-2,000 msec prior to the startle-eliciting stimulus inhibits the amplitude of the response, and (c) a change in the sensory environment less than 10 msec prior to the startle-eliciting stimulus reduces the latency of the response. These findings are consistent with previous research on acoustic elicited startle in the rat. The overall configuration of the results suggests that a pathway including the reticulospinal tract and the bulbopontine reticular nuclei could be the major mediator of startle. In these terms, latency-reduction effects would occur because of partial activation of this pathway, amplitude inhibition would occur because of cerebellar influence, and amplitude facilitation would reflect cerebral or striatal influences.

Acoustic Stimulation↗
PubMed1975

The role of small changes in the acoustic environment in modifying the startle reflex.

When either the intensity or frequency spectrum of an approximately 70-db. SPL narrow-band noise was abruptly changed by a small amount, the rat's response to a startle stimulus presented 64 msec later was inhibited. When similar small frequency changes preceded the startle stimulus by ony 5 msec, the latency of the startle response was reduced, but even relatively large changes in intensity of the antecedent stimulus had no effect on response latency. These findings provide added support for the generalization that the neural processes associated with startle are engaged by small changes in the auditory environment. They also point to a measure of separation between the processes responsible for inhibition and those responsible for latency shift.

Animals↗