Biomedical subjects

R Duclaux

Publications and source records attributed to R Duclaux.

At least 37 records · Page 2Linked to original sources

PubMed1996

Development of cochlear active mechanisms in humans differs between gender.

Despite onset of function early during the third term of gestation, the human auditory system demonstrates continued maturation, thought previously to occur primarily at the neural level. The electromotile properties of outer hair cells appear to contribute substantially to hearing sensitivity and frequency selectivity and lead to the generation of otoacoustic emissions (OAEs). This report demonstrates continued development of cochlear active mechanisms (i.e. end-organ level) after onset of cochlear function, as reflected by OAEs. Significant gender differences also are reported, corresponding to recently observed intersex differences in cochlear length and precursory to gender differences observed in the adult.

Cochlea↗

PubMed1996

Transient evoked otoacoustic emissions in nonsurgical ear.

Several studies have reported contralateral hearing deficits following ear surgery. This study aimed to evaluate changes in micromechanical cochlear properties which could occur in the contralateral ear following ear surgery, using transient evoked otoacoustic emission (TEOAE) recording. Surgery involved tympanic membrane surgery in 13 cases and middle ear surgery in 16 cases. TEOAEs were recorded and compared for contralateral ears before (day 1: D1) and after (day 2: D2) ear surgery. Two patients failed to show a TEOAE reproductibility > 75%, and were excluded from the study, thus reducing the number of patients to 27. Results were compared to those of a control group of 12 normal hearing subjects, recorded in similar conditions also on day one (D1) and day two (D2). The difference between D1 and D2 was not significant in either group. Pre/postsurgery variations in TEOAE amplitude for the patient group were negatively and significantly correlated with the corresponding preoperative levels in that the greater the presurgical TEOAE level, the larger the decrease in postoperative level. Compared to the variation confidence intervals in the control group, TEOAE amplitude remained stable in 15 patients, increased in four and decreased in eight. These three groups of patients differed only regarding preoperative TEOAE amplitude values, which were significantly greater in the group which presented a decrease in TEOAE amplitude than in the others. Increase in TEOAE amplitude was more frequent after tympanic membrane surgery. On the other hand, TEOAE amplitude decrease was more frequent after middle ear surgery, and is significant compared to the tympanic membrane surgery results. The results show that cochlear micromechanical properties may be reduced in the ear contralateral to surgery and that this decrease depends on the severity of the surgical procedures in the operated ear, such as drilling or opening of the oval window.

Acoustic Stimulation↗

PubMed1996

Clinical interest of brainstem auditory evoked potentials in 72 children with inadequate language development.

The present study is of brainstem auditory evoked potentials (BAEP) in 72 children, of 2 to 13 years of age, showing inadequate language development. The age of the children was mainly below the age of 4 (39 cases = 54%), peaking between 3 and 4 years of age (33 cases = 46%). Even so, 82% of our patients were 3 years old or over: 64% were boys, 36% girls, the proportion of boys falling off with age 26% (19 cases) of BAEPs recorded were normal, 74% (53 cases) pathological. High prevalence of undiagnosed hearing loss was found. Physiopathological BAEP classification showed endocochlear impairment in 68% (36 cases), conductive impairment in 21% (11 cases) and retrocochlear impairment in 11% (6 cases) of subjects. Unilateral impairment (20 cases = 28%) cannot account for inadequate language development; but, in the 8 cases (11%) of total bilateral hearing loss, and the 15 cases (21%) of partial bilateral impairment, hearing loss more or equal to 50 dB HL, impaired hearing would play a role in the retardation.

Aging↗

PubMed1995

Influence of auditory stimulation and visual attention on otoacoustic emissions.

Transient Evoked otoacoustical Emissions (TEOAEs) express the micromechanical activity of the cochlear outer hair cells (OHCs). The inhibitory effects of contralateral acoustic stimulation and of visual attention tasks on TEOAE amplitude is well-established. Contralateral auditory stimulation and attention affect cochlear micromechanics via the medial olivocochlear efferent system. The present study is a quantitative comparison of the individual and combined effects of these two inhibitory phenomena in the same subjects. TEOAEs were recorded in seven normal-hearing subjects in absence of inhibitory stimulus (S1), under contralateral 95 dB SPL white-noise stimulation (S2), during a visual attention task (S3) and with simultaneous presentation of both forms of stimulus (S4). Significant reductions in TEOAE amplitude were found with contralateral stimulation (S2) and visual attention (S3) (p = 0.01 and 0.05 respectively, in confirmation of previous studies. The inhibitory effect of combined stimulation (S4) was found to be yet more significant (p = 0.004) than the inhibition obtained with each stimulation presented alone.

Acoustic Stimulation↗

PubMed1995

Spontaneous and evoked otoacoustic emissions in pre-term and full-term neonates: is there a clinical application?

In neonates and infants, hearing impairment leads to impaired language and cognitive development. For that reason, early detection of this sensory deficit is of outstanding importance, particularly in pre-term neonates, who constitute a high risk population in regard to very early acquired hearing loss. Evoked (EOAE) and spontaneous otoacoustic emission (SOAE) recording in 93 pre-term and full-term neonates revealed that this technique is potentially useful for auditory screening in neonatology units. EOAEs and SOAEs can be recorded successfully from 30 weeks of conceptional age. SOAEs were found to be prevalent in females and presented higher peak numbers in right than in left ears. Furthermore, SOAE incidence in pre-term and full-term neonates was found to be high in EOAE positive ears, associated with strong and robust EOAEs.

Acoustic Stimulation↗

PubMed1995

Spontaneous otoacoustic emissions in preterm neonates: prevalence and gender effects.

A number of lines of evidence indicate that the human cochlea is fully functional as a mature sound transducer by 6 months of age. However, information about the development of the active cochlear mechanisms and notably the development of outer hair cell (OHC) activity is yet incomplete. Recording and analysis of otoacoustic emissions (OAEs), probably generated by the OHCs of the organ of Corti, have led to a better understanding, in humans, of how sounds are analysed in the cochlea by means of active mechanisms. Evoked OAEs (EOAEs) and spontaneous OAEs (SOAEs), when they can be recorded in full-term and preterm neonates, show different characteristics from those in adults, suggesting that maturation of the peripheral auditory system is incomplete at birth. To learn more about this maturation, using the best-established facts concerning SOAEs in adults, such as their greater prevalence in females and also in right ears, SOAEs were studied in more detail in 81 preterm neonates, from 30 to 40 weeks of conceptional age, all presenting bilateral EOAEs according to objective criteria. The first finding of this study was that SOAEs existed and could be recorded as of 30 weeks of conceptional age in humans. Some SOAE characteristics in preterm neonates, such as prevalence, peak number and acoustic frequencies, showed similarity with full-term neonates. Comparison of other criteria between the two populations, such as greater SOAE prevalence in right ears and higher SOAE peak number in females, suggested that these developmental factors emerge around term in humans. Comparison of SOAE characteristics between male and female preterms suggested that male preterms were less advanced in peripheral auditory development than were female preterms.

Acoustic Stimulation↗

PubMed1995

Influence of hyperthermia on cochlear micromechanical properties in humans.

We investigated the effect of body temperature on transient evoked otoacoustic emissions (TEOAEs) in humans. Hyperthermic conditions were obtained in adults in a climatic chamber. During hyperthermia up to an average temperature of 38.4 degrees C, significant falls were found in total amplitude and peak values of TEOAEs: by 1.3 dB SPL/degree C and 2.3 dB/degree C, respectively. This inhibition affected all spectrum components equally. These findings indicate that the outer hair cell micromechanical activity that is presumed to be measured by TEOAEs is not independent of variations in body temperature. The reduction found in hyperthermia suggests that temperature-dependent mechanisms are involved in the generation of TEOAEs.

Adult↗

PubMed1995

[Sonomotor vestibular reflex in acoustic neuroma].

Despite recent advance in diagnosis and surgical techniques of acoustic neuroma, ideal criteria for hearing preservation attempt remain unsatisfactory. This study reports sonomotor vestibular reflex recorded pre and postoperatively in 20 patients with acoustic neuroma. Hearing preservation was attempted according to tumor size and preoperative pure tone audiometry results. The studied population was divided in 2 groups according to hearing preservation was attempted (group 1 n = 13, retrosigmoid approach) or not (group 2 n = 7, translabyrinthin approach). In accordance with postsurgical audition, the subjects of group 1 were distributed in group 1-A (postsurgical preserved audition n = 4) or group 1-B (postsurgical unpreserved audition n = 9). Presurgical sonomotor vestibular reflex in response to pathological stimulation were compared in the different groups. In preoperative period, sonomotor vertibular reflex in response to pathological side stimulation were present in all the patients of group 1-A with a similar amplitude to those obtained when stimulating healthy side. In 6 subjects of group 1-B these responses were present but with a smaller amplitude than those obtained when stimulating healthy side. The responses were absent in 3 subjects of group 1-B and in all the subjects of the group 2. These result tend to demonstrate that preoperative presence of sonomotor vestibular reflex in response to neuroma side stimulation with amplitude similar to those obtained by healthy side stimulation is a favorable criterion for hearing preservation attempt. On the opposite, the decrease in the amplitude of these responses or their absence seems to be unfavorable for hearing preservation attempt.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

Lack of association between transiently evoked otoacoustic emission amplitude and experimentation linked-factors (repeated acoustic stimulation, cerebrospinal fluid pressure, supine and sitting positions, alertness level).

Changes in transiently evoked otoacoustic emissions (TEOAEs) occur during sleep and during tasks requiring attention. This can be due to a central nervous system effect on the cochlea. But, an additional or dominant influence by non-controlled factors is possible. In this paper, the effect of click-stimulus repetition, lying and sitting positions, state of alertness (awake or asleep) and CSF pressure variation on TEOAE features were studied. None of these factors affected TEOAE amplitude. In 2 subjects, TEOAE amplitude increased considerably during the night while remaining stable in 7 subjects during daytime sleep. This may be due to circadian variations of TEOAE amplitude.

Acoustic Stimulation↗

PubMed1993

Contralateral auditory stimulation alters acoustic distortion products in humans.

It is now generally accepted that otoacoustic emissions (OAE) represent the only objective and non-intrusive means of functional exploration of the active micromechanical characteristics of the outer hair cells of the organ of Corti. Previous studies showed a decrease of the transiently evoked otoacoustic emissions and spontaneous otoacoustic emissions in humans, during acoustic stimulation of the contralateral ear, and attributed this effect to the medial efferent system. Such an effect has been shown on acoustic distortion product otoacoustic distortion emissions (DPOAE) in guinea pigs, but has not been investigated for DPOAEs recorded in humans, although DPOAEs represent the easiest means of exploring active micromechanical cochlear properties both in humans and in laboratory animals. The present study sought to investigate the existence and characteristics of a contralateral auditory stimulation effect on DPOAEs recorded in humans. This study shows that contralateral broad-band noise (BBN) has a suppressive effect on DPOAEs recorded from 0.5 kHz to 5 kHz. This effect is not due to air conduction, as no change in the noise floor occurred under increasing contralateral stimulation, and as no reduction in DPOAE amplitude was obtained in subjects whose contralateral ear was sealed with a plastic ear plug. Moreover, cross-over attenuation by bone transmission has been ruled out, as no change in DPOAE amplitude was recorded in the healthy ear of total unilaterally deaf patients during acoustic stimulation of the deaf ear. The effect seen was not entirely due to the acoustic reflex, as it was found and could indeed be even greater in subjects with no acoustic reflex. Results presented here show that the contralateral BBN effect is greater at low levels of ipsilateral stimulation, which leads us to discuss the involvement of both passive and active mechanisms in DPOAE generation at high stimulation levels. The contralateral BBN effect seems to be greater in mid frequency cochlear regions. There is strong evidence that the medial efferent system is involved and that afferent and efferent inputs are, at least partly, integrated at a brainstem level in order to ensure cochlear interaction. DPOAEs provide an interesting model for functional exploration of the efferent system, since they seem to be the only type of otoacoustic emission that can be recorded in both humans and in the majority of animals, and since results are obtained in the same way from both animals and humans, which allows experimental animal models very close to the human model.

Acoustic Impedance Tests↗

PubMed1993

Naltrexone improves blood gas patterns in obstructive sleep apnoea syndrome through its influence on sleep.

Endogenous opiates have been shown to depress ventilation, and could therefore play a role in sleep apnoea syndrome (SAS). Hence, opiate antagonists have been used to treat SAS. The improvement they seem to give in blood-gas monitoring could derive either from a direct blocking of endorphins that inhibit respiration or else, indirectly, through an influence on sleep patterns. The present study used a double blind cross-over protocol to investigate the relationships between the effects on blood-gas and on sleep patterns of the oral opiate antagonist naltrexone in obstructive SAS. Sleep patterns and transcutaneous blood gas (tcPO2 and tcPCO2) were recorded in parallel. Control recordings, without treatment, were carried out over two nights, followed by two nights of recording after administration either of naltrexone followed by a placebo or of a placebo followed by naltrexone. The number of obstructive apnoea and hypopnoea events per hour of sleep (Apnoea-Hypopnoea Index: AHI), of hypoxic events (defined as a tcPO2 fall of at least 10, 15 or 20 mm Hg) and of hypercapnic events (defined as a tcPCO2 increase of at least 5 mm Hg) were counted. A Metabolic Suffering Index (MSI) was calculated, defined as the product of the number, duration and magnitude of hypoxic and hypercapnic events. Compared to placebo, naltrexone resulted in significant improvements in blood-gas patterns for the duration and MSI of hypoxic events and for the number, duration and MSI of hypercapnic events. Likewise, compared to placebo, naltrexone induced significant decreases in total sleep time, slow-wave sleep and rapid eye movement (REM) sleep, and, on the other hand, significant increases in total wake time and in the number of wakenings per hour of sleep (Nw h-1). Certain naltrexone-linked blood-gas improvements were closely correlated with certain of the sleep pattern changes: the decrease in number and duration of hypoxic events correlated with REM-time decrease and the decrease in number and duration of hypercapnic events correlated with the increase in Nwh-1. These findings suggest that the improvement in blood-gas patterns induced by naltrexone in SAS may be mediated by sleep pattern effects: i.e. a decrease in REM-time and an increase in intra-sleep wakening.

Journal Article↗

PubMed1991

Hemispheric asymmetry of late auditory evoked response induced by pitch changes in infants: influence of sleep stages.

Late auditory evoked potentials (LAEPs) have been recorded in response to a 1000 Hz standard (occurrence 80%) or a 2000 Hz deviant (occurrence 20%) tone on the left (T3) and right (T4) temporal scalp in 6-week-old full-term newborns during pure quiet or active sleep states. Sleep states were premanently controlled by polygraphic recording including EEG, EOG, EMG, EKG and respiratory movements. During quiet sleep LAEPs consisted of a clear polygraphic response: N1-P2-N2-P3. Mean latencies ranges on T3 and T4 were: N1 = 28-70 ms; P2 = 343-407 ms; N2 = 966-1178 ms; and P3 = 1461-1492 ms. During active sleep LAEPs consisted of a N1-P2-N2 response. Mean latency ranges on T3 and T4 were: N1 = 36-79 ms; P2 = 278-304 ms; N2 = 555-620 ms. N2 latency was significantly shorter in AS than in QS. Amplitude of the N1-P2-N2 complex was significantly lower during active sleep. In response to standard stimuli, mean amplitudes and latencies of the LAEP were similar on T3 and T4 during active or quiet sleep states. In response to deviant stimuli mean amplitude of the N1-P2-N2 complex was significantly higher and mean latencies of N1 and N2 were significantly shorter on T3 during quiet sleep. No significant difference was observed during active sleep. These results confirm that sleep stages have a considerable influence on cortical auditory pathways. The auditory message is amplified during quiet sleep and inhibited during active sleep. Therefore sleep states need to be controlled to analyze LAEPs in young children.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗

PubMed1991

Effect of contralateral acoustic stimulation on active cochlear micromechanical properties in human subjects: dependence on stimulus variables.

1. Outer hair cells (OHCs) have active micromechanical properties that are thought to be the origin of evoked otoacoustic emissions (EOAEs). In the present study, click-evoked otoacoustic emissions were recorded in humans with or without various contralateral acoustic stimulations. A previous study, concentrating on contralateral stimulation with broadband noise, had shown a decrease of the EOAE amplitude in humans. Results support a role for the efferent system in cochlear mechanics; indeed, medial efferent neurons of the olivocochlear bundle terminate on the OHCs. To obtain a better understanding of the medial efferent system functioning in humans, the present study looked at the contralateral suppressive effect as a function of stimulus parameters. 2. The study of the input-output function of the EOAE amplitude with and without a 50-dB SPL contralateral broadband noise showed that the suppressive effect was equivalent to a mean reduction of 3.77 dB. 3. For the EOAEs to tone pips, the contralateral suppressive effect was strongest when the contralateral ear stimuli were narrow bands that were centered around the central EOAE frequency. This frequency specificity disappeared for contralateral narrow band noise levels greater than 50 dB SPL. 4. The contralateral suppressive effect was also observed with transient contralateral sounds (nonfiltered clicks). Significant reductions of the EOAE amplitude were seen with contralateral click levels as low as 17.5 dB SL. Above this level, the EOAE amplitude decreased as the contralateral stimulus level increased. This effect was still present in subjects without any stapedial reflex, but absent in total unilateral hearing-loss subjects. Therefore this suppressive effect is unlikely to be due to alteration of the middle ear function or to transcranially conducted sound. 5. When the contralateral interclick interval exceeded 14.2 ms. the suppressive effect was smaller. With contralateral stimulus level maintained subjectively constant, the effect was found to disappear when the interclick interval was greater than 49.9 ms. A saturation of the contralateral suppressive effect was observed for click rates greater than 70/s (interclick interval less than 14.2 ms). 6. Our study confirms and specifies the contralateral sound suppression effect on cochlear mechanisms in humans, assessing the equivalent reduction, showing a frequency specificity and extending these findings to contralateral transient sounds. Any influence of the acoustic crosstalk was eliminated. A role played by middle ear muscles cannot be absolutely ruled out but is not necessary to produce such a contralateral suppressive effect (the effect being found in subjects after surgical removal of the stapedius muscle) and could not explain the frequency specificity.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗

PubMed1991

Electrophysiological correlates of auditory lexical decision: an attempt to test the "Cohort Model".

The electrophysiological correlates of spoken word recognition were investigated in an auditory lexical decision task. N4 and P7 waves were found at Cz and Pz for both words and nonwords, with significantly higher peak amplitudes for the latter; this result was independent of subject's sex and of hand usage for the task response. The results were then analyzed in terms of the "Recognition Point" for words and nonwords as defined in Marslen-Wilson's "Cohort Model" of auditory word recognition (Marslen-Wilson & Welsh 1978). A correlation was found between nonword "Recognition Point" latency and the associated late positive wave. The contribution of the "Cohort Model" to electrophysiological investigation of auditory word-recognition is discussed.

Adult↗

PubMed1990

Effect of contralateral auditory stimuli on active cochlear micro-mechanical properties in human subjects.

The present study investigates the possibility that contralateral auditory stimulation along medial efferent system pathways may alter active cochlear micromechanics and hence affect evoked oto-acoustic emissions in humans. A first experiment, involving 21 healthy subjects showed reduction of oto-acoustic emission amplitude under low intensity contralateral white noise (from 30 dB SPL, 10 dB SL, upwards). The effect is found for intensities below the acoustic reflex threshold (85.2 dB HL). A second experiment, involving 10 of the above 21 subjects, sought to rule out any technical artefact. Recording was again carried out, but after sealing of the contralateral ear with a silicon putty plug. No contralateral intensity effect on oto-acoustic emission amplitude was found for contralateral intensities below 65 dB SPL. In subjective perception terms (dB SL) an effect was found under sealing when the sound reached or passed above the 10 dB SL level. These two findings confirm the preceding experiment. The third experiment investigated the role of transcranial transmission of the contralateral auditory stimulus. 16 subjects having total unilateral deafness and one healthy ear were tested by the same procedure as above. No fall-off in oto-acoustic emission amplitude was found for contralateral stimuli equal to or less than 80 dB SPL. There is thus a contralateral auditory stimulus effect on active cochlear micromechanics. The most appropriate explanation involves the medial cochlear efferent system, excited at brainstem level via the afferent auditory pathways. Alteration of active cochlear micromechanics seems promising at a basic level, pointing, as it does, to an interactive cochlear functioning which can be investigated by simple, non-intrusive, objective techniques which can be used with human subjects. We have here a model for functional exploration of the medial olivocochlear efferent system.

Acoustic Stimulation↗

PubMed1988

Effect of sleep on middle latency response (MLR) in infants.

Auditory middle latency responses (MLR), with two click-rates (1.3 Hz, 8.9 Hz) and simultaneous polygraphic recording with EEG, EOG, EMG, ECG and respiratory rhythm have been recorded in 16, 6 or 7 week old infants to study the effect of sleep on the amplitudes of MLR. For both click-rates, response amplitude depended upon waking and sleep states, the Na-Pa complex being always greater during waking states. It is of very low amplitude during quiet and active sleep but significantly lower in quiet sleep. In some infants it disappears entirely in quiet sleep. MLRs have been said to be hard to reproduce in infants. Our results would suggest that this is due to a strong alertness effect on MLRs in infants.

Age Factors↗

PubMed1988

Cerebral evoked potentials after endorectal mechanical stimulation in humans.

Although numerous clinical studies have proved that impaired rectal sensation is a major factor in fecal continence dysfunctions, objective studies in this field are still lacking. To provide information on normal rectal afferents, a study of cerebral potentials evoked by mechanical stimulation of the rectal wall was carried out in 10 healthy volunteers (5 male, 5 female; age, 33-52 yr). The stimulating device consisted of a rectal balloon rhythmically inflated and deflated by means of an animal breathing ventilator. Recordings were obtained 2 cm behind the vertex (C'z, International system 10-20). The responses were averaged from 300 to 800 sweeps. The average was triggered either on inflation ("on effect") or on deflation ("off effect"). Inflation volume and pressure were adjusted to induce a clear but not painful pulsing sensation. Reproducible responses were recorded by both on and off effects. The evoked potentials were polyphasic with a succession of positive and negative waves (peak latencies between 78 and 310 ms). The shape of the response (morphology, latency, and amplitude) was perfectly reproducible in the same subject. With regard to intrasubject reproducibility, variability was displayed: only the early waves (latency less than 100 ms) were perfectly reproducible; late waves exhibited variable latency and morphology. The present findings are the first demonstration of the possibility of recording an evoked potential on the scalp after a mechanical stimulation of the rectum.

Adult↗

PubMed1987

Hemispheric lateralization of emotions: absence of electrophysiological arguments.

EEG lateralization was examined during happy and sad emotional expression in 24 subjects. Happy and sad emotional states were induced by asking subjects to mentally review previously shown film-sequences. Our results failed to replicate those of previous studies, in that they showed no frontal alpha lateralization as a function of emotion. The authors discuss the literature and suggest caution before asserting the existence of electrophysiological arguments in favor lateralization of emotions in humans.

Adolescent↗