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Biomedical subjects

A Morgon

Publications and source records attributed to A Morgon.

At least 235 records · Page 13Linked to original sources
PubMedDate not supplied

Evoked and spontaneous otoacoustic emissions. A comparison of neonates and adults.

Evoked otoacoustic emissions (EOAEs) and spontaneous otoacoustic emissions (SOAEs) were compared between neonates and adults. Several differences were seen for EOAEs: (i) the occurrence of EOAEs was significantly greater in adults than in neonates, and in neonates it increased with extra-uterine age; (ii) the high frequency EOAE intensity was greater in neonates than in adults; (iii) the EOAE intensity was significantly greater in neonates than in adults. No age-related differences for SOAEs were found: (i) age was not significantly related to the presence/absence of SOAEs in neonates or adults; (ii) the occurrence of SOAEs was, however, significantly greater in females than in males in both neonates and adults.

Acoustic Stimulation↗
PubMedDate not supplied

Maturation and effect of stimulus rate on brainstem auditory evoked potentials.

Brainstem auditory evoked potentials (BAEPs) at three stimulus rates (20, 41.3 and 61.3 c/s) were recorded in 104 normal preterm infants, distributed in four age groups between 32 and 39 weeks (conceptional age), and in 20 normal adults. The latency shifts between 61.3 c/s and 20 c/s, and between 41.3 c/s and 20 c/s, were calculated for each wave, and studied as a function of age. A significant effect of conceptional age was shown on the '61.3-20 c/s' and the '41.3-20 c/s' wave V latency shifts, and a significant difference between adults and newborns was noted for the wave V and wave III latency shifts. No significant difference was obtained for the wave I latency shifts. This suggests that the changes of auditory adaptation with maturation may be predominantly at a central level, i.e. on central synapses.

Acoustic Stimulation↗
PubMedDate not supplied

Control by the evoked potential of the brain stem of the administration of dibekacine in premature infants.

The administration of dibekacine to 10 newborn carriers of a germ infection--or staphylococcus, was controlled for auditory tolerance. The auditory threshold was controlled by the evoked potential of the brain stem. Medication never caused the threshold to change. The evolution of latency in waves J1, J3 and J5 could not be seen except in wave 1 where latency decreased, as can be seen in other premature infants of babies born at term.

Auditory Threshold↗
PubMedDate not supplied

Anatomical parameters of the voice.

Analysis of the anatomical parameters of the voice allows us to observe the relations--which exist not only within the cortical centres but also in the underlying centres--between structures governing phonation functions and those concerned with the functions of hearing and of language. Voice, articulation, speech, language and hearing are so many elements of one and the same function of communication.

Auditory Cortex↗
PubMedDate not supplied

Maturational changes in the intensity latency relation of the brainstem auditory evoked potentials in humans.

The effects of stimulus intensity variation on brainstem auditory evoked potentials have been studied on 111 preterm, 36 fullterm neonates and 50 adults. When intensity decreases the lengthening of latencies is greater in preterm neonates. This effect is clearer with wave I than waves III and V and suggests an immaturity of the basal part of the human cochlea in preterm neonates.

Acoustic Stimulation↗
PubMedDate not supplied

Experimental study of collagen as eardrum graft support in dogs.

This experimental study involving dogs tested type IV human collagen as a biomaterial for use in the tympanic membrane reconstruction. A loss of substance was induced for the two tympanic membranes, and a type IV collagen graft made to one side. The kinetics of receiver fibroblast colonisation of the graft, as well as in the case of resorption, were studied. Anatomopathological examination revealed the process of reconstitution. This animal study prepares the way for studies on man.

Animals↗
PubMedDate not supplied

Auditory-evoked brainstem responses elicited by maximum-length sequences in normal and sensorineural ears.

Auditory brainstem responses (ABRs) were recorded using pseudo-random pulse trains called maximum-length sequences (MLSs), which allow high stimulus rates and simultaneous recording from both ears, and were compared to ABRs obtained by conventional averaging. In normally hearing subjects, ABRs by MLSs produced the same waves as conventional ABRs, although wave latencies increased and amplitudes decreased. In normal as in sensorineural ears, MLS-ABR thresholds were similar to conventional ABR thresholds (except when binaural recordings were made) and were correlated with high-frequency audiometric thresholds. Binaural MLS-ABR recordings represent the individual response of each ear, as shown by recordings of monaurally deaf subjects.

Acoustic Stimulation↗
PubMedDate not supplied

Auditory brainstem response (ABR) latency: relative importance of age, sex and sensorineural hearing-loss using a mathematical model of the audiogram.

Influences of age, sex and audiogram on ABR latencies have been studied. Using a mathematical model of audiogram, the analysis of data finds a relative importance of age, sex and audiogram similar to previous studies. Audiogram slope was correlated only with the latencies of waves I and V, and multiple regression analyses indicate the slope effect is relatively weak compared to that of the other parameters. Using a mathematical model of audiogram did not improve the ABR variance across subjects, underscoring the need to discover other relevant variables to explain ABR latency.

Acoustic Stimulation↗
PubMedDate not supplied

Differential maturation of brainstem auditory evoked potentials in preterm infants according to birthweight.

Brainstem auditory evoked potentials (BAEPs) were recorded from 39 preterm infants, divided into 3 groups: small-for-gestational-age, with a birthweight less than or equal to 1500 g (SGA); appropriate-for-gestational-age, with a birthweight less than or equal to 1500 g (AGA1); and appropriate-for-gestational-age, with a birthweight higher than 1500 g (AGA2). A significant shortening of the I-V interval due to an increase in wave I latency was found in the SGA group. The lower-weight AGA group (AGA1) was never significantly different from the SGA group. Although there was no correlation between conceptional age and weight at the time of the examination for the studied population, negative correlations were found between wave I latency and weight at the time of the examination. These findings confirm previous research and suggest the existence of a link between weight and basal cochlear maturation.

Acoustic Stimulation↗
PubMedDate not supplied

Contralateral suppression of transiently evoked otoacoustic emissions and tinnitus.

The present paper reports individual data obtained in three different patients who consulted for unilateral tinnitus in the Department of Otolaryngology. After pure tone and high-frequency audiometry, Audioscan audiometry was recorded, and tinnitus measurement which comprised a determination of pitch and loudness matches. Spontaneous, transient evoked and 2f1-f2 distortion product otoacoustic emissions at 65 dB SPL stimulus intensity were then determined. The functioning of the medial olivocochlear system (MOC) was also tested from a comparison between OAE input/output curves obtained in the presence and absence of 30 dB SL contralateral stimulation by a broadband noise: MOC global effectiveness was assessed through transient evoked emissions while those concerning distortion product emissions allowed a precise testing at the tinnitus frequency itself. The examples here displayed illustrate the diversity of results that can be found in such investigations, thereby preventing a general law to be established from the global testing of MOC functioning. On the contrary, the local testing at the precise frequency of tinnitus revealed the existence of an alteration of MOC functioning in at least one ear as shown by either a weak, null or inverse effect of contralateral stimulation. A better understanding of the sensorineural forms of tinnitus should come from the extensive investigation of MOC efficiency along the basilar membrane when routine clinical investigations lead one to suspect an involvement of this system, due to discordant damaging between inner and outer hair cells. Such studies would allow one to test the validity of hypotheses which invoke MOC-related mechanisms as an essential link for the emergence and persistence of tinnitus.

Acoustic Stimulation↗