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Biomedical subjects

N Dillier

Publications and source records attributed to N Dillier.

41 records · Page 3Linked to original sources
PubMed1978

Activation of an inhibitory noradrenergic pathway projecting from the locus coeruleus to the cingulate cortex of the rat.

Repetitive stimulation of the locus coeruleus evoked strong inhibition of the firing rate of about 50% of cells of the cingulate rat cortex. Forty per cent of the cells were not affected and 9% were excited by stimulation of the locus coeruleus. Pretreatment of the rats with reserpine and alpha-methyl-p-tyrosine drastically reduced the percentage of cells inhibited by locus coeruleus stimulation. The cells inhibited in response to stimulation of the locus coeruleus as well as those not inhibited were depressed by microiontophoretically applied norepinephrine. This inhibitory action of NE was observed in rats anesthetized either with urethane, chloral hydrate or with Nembutal. The transsynaptically elicited, as well as the norepinephrine elicited, depression of the cells' discharge rate was antagonized by the microiontophoretically applied beta-receptor blocking drug MJ 1999. These data suggest that the inhibitory action on cingulate cortical cells of locus coeruleus stimulation is mediated by the dorsal ascending noradrenergic pathway.

Adrenergic Fibers↗
PubMed1978

[Electrical stimulation of hearing in humans: a survey of the actual state of development of an implantable prosthesis for sensorineural deafness (author's transl)].

Recent clinical results show that electrical excitation of hearing sensations with implanted electrodes in the inner ear can be successful in suitable deaf persons. A critical literature review shows that some results have been described too vaguely and that there still exist numerous methodical and technical deficiencies. Even with multichannel stimulation, true tonotopical hearing could not be achieved. Periodicity hearing alone is not sufficient for the discrimination of one-syllable words. However, most deaf persons fitted with surgically implanted electrodes judged the new hearing sensations as being agreeable and quite useful. There seem to be no long term harmful effects of these implants upon the state of the acoustic nerve. However there are still a series of basic questions in auditory physiology pending which can only be solved through intensive collaboration of the clinical disciplines involved.

Animals↗
PubMedDate not supplied

A simple two-component model of the electrically evoked compound action potential in the human cochlea.

Neural response telemetry (NRT) permits in situ intracochlear recordings of the electrically evoked compound action potential from the auditory nerves using scala tympani electrodes. The recorded NRT waveforms can generally be categorized under either single positive peak or double positive peak waveforms. This is similar to the observations from Stypulkowski and van den Honert, who suggested that the double peak complex arises from two components that could be axonal and dendritic in origin, respectively. Using a simple mathematical model which linearly combines two separate waveforms similar in shape but differing in amplitude and latencies, it was possible to simulate the various NRT waveform categories. The simulation results support the view that the two waveform components originate from dendritic or axonal processes and implies that the shape of the response waveform may provide information about the degree of neural survival in the stimulated cochlea. This information could be useful for determining optimal speech coding parameters for cochlear implant users on an individual basis.

Cochlea↗
PubMedDate not supplied

Multicentric field evaluation of a new speech coding strategy for cochlear implants.

In a multicentric study involving 4 European cochlear implant centers, the speech perception abilities of 20 native German-speaking individuals implanted with the Nucleus 22 Channel Cochlear Implant System when using a new spectral peak (SPEAK) speech coding strategy were investigated. This strategy continuously analyzes the speech signal using 20 digital programmable bandpass filters and presents up to 10 spectral maxima to the 22 implanted electrodes. Each subject's performance on a variety of auditory perceptual tasks was evaluated with the experimental encoder (SPEAK), relative to his or her performance in a reference condition. An ABAB experimental design was used whereby each strategy was reversed and replicated. The reference levels of auditory performance were established using the multipeak (MPEAK) speech-processing strategy of the Nucleus speech processor. Only subjects who achieved open-set monosyllable word recognition in the reference condition were included in this study. Significant differences in group mean scores for most speech recognition subtests were obtained for the SPEAK versus the MPEAK strategy. The largest overall improvements were observed for the sentence tests under noisy conditions.

Cochlear Implants↗