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Biomedical subjects

L Collet

Publications and source records attributed to L Collet.

At least 91 records · Page 5Linked to original sources
PubMed1996

Ipsilateral ABR with cochlear implant.

Ipsilateral ABR recording technique was developed with the MXM DIGISONIC DX10 cochlear implant, involving, firstly, setting of recording variables with regard to implant and ABR constraints, and, secondly, enhancement of recording quality by signal processing. The resulting recording quality then enabled us to characterize ABR latency, amplitude and wave reproductibility according to stimulus intensity and stimulation site (electrode stimulated). The findings agree with those of the literature on contralateral human and ipsilateral animal studies. Waves III and V amplitude increased with stimulus intensity. Waves III and V latency was insensitive to stimulus intensity or site. ABR quality diminished basally.

Cochlear Implants↗
PubMed1996

A new stimulation strategy for recording electrical auditory evoked potentials in cochlear implant patients.

Recording electrical auditory brainstem responses (EABR) provides clinical insight about responses of the residual post-cochlear neural system to electrical stimulation in profoundly deaf patients. A new strategy is presented for stimulating patients already implanted with a 15-electrode cochlear implant. Since the device is fully re-programmable via a RS-232 PC interface, it was possible to load a specific stimulating strategy designed to improve the spatial locus and the temporal structure of the impulse stimulation. Waves III to V emerge more clearly when this method is applied.

Adult↗
PubMed1995

Evidence of a medial olivocochlear involvement in contralateral suppression of otoacoustic emissions in humans.

Otoacoustic emissions (OAEs) evoked by click stimuli were recorded in both ears of 20 normal human subjects, in the presence and absence of a contralateral masking broad band noise. No difference in the amplitude of OAE suppression was noted between the first tested ear and the second one. In addition, 20 pathological subjects were tested according to the same protocol. Ten of them belonged to a group of patients whose vestibular nerve was sectioned on one side to relieve incapacitating vertigo and thus represented a group in whom olivocochlear efferents were severed. A great reduction of suppression observed in the operated ear suggested that olivocochlear efferent fibers are necessary to obtain a full suppressive effect. Three of the pathological subjects were patients who had undergone a decompression of the facial nerve which necessitated the same surgical approach as vestibular neurotomy, but without any section of vestibular fibers. This surgical control group demonstrated that the surgical act by itself cannot explain the difference observed in the neurotomized group. Finally, seven of the pathological subjects were patients with Bell's palsy, which paralyses the facial nerve and abolishes the stapedial reflex. No suppression difference was observed between healthy ears and ears without stapedial reflex. Therefore, it appeared that the stapedial reflex was not involved in the contralateral suppression of EOAEs. However, as the tensor tympani muscle remained functional in these patients, its involvement in the suppressive effect cannot be excluded.

Adult↗
PubMed1995

Medial olivocochlear system and loudness adaptation: differences between musicians and non-musicians.

Simple loudness adaptation and crossed olivocochlear feedback were investigated--through the Tone Decay Test (TDT) and Transiently Evoked Otoacoustic Emission (TEOAE) recording, respectively--in a sample of normal-hearing subjects including both musicians and non-musicians. The results for musicians and non-musicians differed statistically: the musicians showed on average less loudness adaptation and a greater reduction in TEOAE amplitude under contralateral acoustic stimulation, suggesting a stronger medial efferent feedback on the auditory periphery in these subjects. This finding, that not only psychoacoustic performance but also the physiological mechanism is different in musicians, strongly suggests that the latter should, like the former, be influenced by auditory "training" such as music studies. This perspective is discussed in detail in the text, since it raises puzzling questions and outlined promising issues in the field of auditory psychophysiology.

Audiometry, Pure-Tone↗
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

Effect of interstimulus interval on evoked otoacoustic emissions.

In order to explore extensively the effect of interstimulus interval, including very short interstimulus intervals, on evoked otoacoustic emissions (EOAEs), several EOAE recordings were carried out using pairs of clicks: a suppressor click preceded the stimulus click generating an EOAE, with various intervals between the two clicks. EOAEs elicited by two clicks separated by intervals under 8-9 ms had significantly smaller amplitudes than EOAEs evoked by the stimulus alone. The amplitude decay correlated with the interclick interval, and was about 40% when the interclick interval decreased from 12 to 1 ms. This phenomenon has been noted before but not precisely quantified. It might reflect an adaptive mechanism within the outer hair cells, which has been previously described, or else mechanical interactions on the basilar membrane. The delay in EOAE decrease is of the same order as the first phase of neural adaptation, known as 'rapid adaptation', and these thus may prove to be correlated.

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

Contralateral suppression of evoked otoacoustic emissions and detection of a multi-tone complex in noise.

Although some findings suggest that auditory efferent fibers are involved in perception in noise, their function remains controversial. The contralateral suppression of evoked otoacoustic emissions (EOAEs) has recently provided a means of exploring the medial olivocochlear system (MOCS) in humans. In an experiment based on this paradigm, the present study examined the relationships between variations of both EOAEs and detection-in-noise thresholds, induced in the same subjects by a contralateral 50-dB-SPL broad-band noise masker. EOAEs were recorded in response to a burst of a multitone complex composed of 1, 1.5 and 2-kHz components. The detection thresholds of this 3-component complex were measured at 2 ipsilateral noise levels: 50 and 70 dB SPL. The main finding was a significant correlation between EOAE suppression and threshold variations under contralateral masking. A relationship was also found between the contralateral suppression of EOAEs and threshold variation induced by the increase in ipsilateral noise level. These findings support the notion that the MOCS is involved in the detection of multicomponent stimuli in noise.

Adult↗
PubMed1995

Physiopathological investigations in a family with a history of unilateral hereditary deafness.

We examined several members of the same family with unilateral sensorineural hearing loss. The defect showed dominant inheritance. Clinical examination and auditory tests, including high-definition audiogram and otoacoustic emission recording, were done to characterize the physiopathological process of hearing loss, and to investigate possible asymptomatic auditory features in the normal ear of affected subjects and nonaffected siblings. Hypotheses as to the underlying mechanisms are discussed, eg, variable expression of bilateral isolated hereditary deafness, incomplete Klein-Waardenburg syndrome with stria vascularis anomalies and highly variable gene expression, or unilateral cochlear aplasia. The phenomenon may also be related to the delayed progressive unilateral loss in patients with bilateral hereditary deafness, involving perhaps unilateral vascular disorders or a genetically induced degeneration of cochlear cells or auditory neurons.

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

Influence of aging on active cochlear micromechanical properties and on the medial olivocochlear system in humans.

Transiently evoked otoacoustic emissions (TEOAEs) without and with contralateral acoustic stimulation (CAS), as well as distortion product otoacoustic emissions (DPOAEs), were recorded on 60 subjects divided into 2 groups, the first constituted by 38 normally hearing young subjects and the second by 22 subjects aged from 70 to 88 years and with normal hearing levels in view of their age. TEOAEs and DPOAE 'audiograms' were recorded in a third group constituted by 15 subjects with ages ranging from 6 to 57 years and with hearing levels not significantly different from those of the second group for frequencies above 500 Hz. TEOAEs were present in 100% of the subjects in the first group and in 91% in the second group, although with smaller amplitude. The fall in TEOAE amplitude under CAS was smaller in the second group. Concerning DPOAE audiograms, in the first group, a response was found in 71 to 95% of cases for frequencies ranging from 1 to 6.35 kHz, and in 7 to 37% of cases in the second group. Mean amplitudes were significantly lower in the second group for frequencies ranging from 2.83 to 5.04 kHz. group for frequencies ranging from 2.83 to 5.04 kHz. Mean 'thresholds' ranged from 38.55 to 43.57 dB SPL for frequencies ranging from 1 to 6 kHz in the first group and from 50 to 58 dB SPL in the second group. No significant difference was found between the second and third groups concerning the amplitude and spectrum of the TEOAEs and DPOAE audiograms. Thus, age influences TEOAEs, DPOAEs and the effect of CAS on TEOAEs.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1994

Auditory selective attention in the human cochlea.

According to current theories, auditory selective attention alters the sensory analysis of acoustic inputs only in the central auditory system. Despite numerous attempts, no evidence of attentional selection has been found in the auditory periphery. Measurements of evoked otoacoustic emissions (EOAEs) during a selective dichotic listening task showed that the EOAEs to tones in one ear had larger amplitude when attention was directed to this ear than when attention was directed to the opposite ear. The results indicate that genuine effects of auditory selective attention can be observed at the cochlear receptor.

Acoustic Stimulation↗
PubMed1994

Attention and otoacoustic emissions: a review.

The possible existence of an attention effect on the peripheral auditory system remains a controversial issue. The aim of the present study is to show the possible contribution of otoacoustic emissions towards demonstrating cognitive control of peripheral auditory processes via the auditory efferent fibers. This measurement technique allows investigation of a further part of the peripheral auditory pathways and of whether efferent fibers, presumably involved in cochlear neurosensory activity, could mediate an attention effect by the selection of auditory information.

Acoustic Stimulation↗
PubMed1994

Differential effects of visual attention on spontaneous and evoked otoacoustic emissions.

A visual task decreases evoked otoacoustic emissions (TEOAE) to an interindividually variable degree. The aim of these two studies was to assess whether the presence or absence of spontaneous otoacoustic emissions (SOAE) is involved in this variability. The first experiment investigated spontaneous otoacoustic emission (SOAE) frequency shifts during a visual attention task with a Fast Fourier Transform analysis, and found no attention effect on SOAEs. Using a larger subject pool, the second experiment concerned the attention effect on transiently evoked otoacoustic emissions and SOAE amplitude, using different measurement methods with the same visual task. The sample was composed of two groups of subjects: group A comprising subjects presenting SOAEs and group B subjects without SOAEs. A decrease in EOAE amplitude for group B during attention was observed and seems to confirm a possible influence of attention on the cochlea via the medial olivocochlear efferent system (MOES). The TEOAE amplitude of group A did not vary during attention, showing the peculiarity of this population of subjects and suggesting a different cochlear functioning.

Acoustic Stimulation↗
PubMed1994

On the role of the olivocochlear bundle in hearing: a case study.

A young patient with normal pure-tone thresholds in both ears underwent a unilateral vestibular neurotomy in January 1992 to relieve severe vertigo ascribed to Ménière's disease. Evidence is provided that the whole vestibular nerve including the olivocochlear bundle (OCB) was sectioned. Just prior to the surgery, the patient was examined in several psychoacoustic tests involving mainly signal detection and selective attention. Over the next 20 months, he was reexamined in those same tests. The patient's ability to detect expected tones in the quiet (including audiograms) or in noise was the same as before the surgery. The one change was a marked improvement in the detection of unexpected signals in noise, which appears to reflect impaired selective attention. During those 20 months, new tests were also performed on discrimination, loudness, pitch, lateralization, and temporary threshold shift. On these tests, the only differences between the operated and unoperated ears concerned binaural diplacusis and loudness adaptation close to threshold, but these differences may well have been present prior to the surgery. Except with respect to what is probably selective attention, we uncovered no other clear role for the OCB in hearing. This outcome agrees with limited measurements on other patients, with their subjective reports, and with a number of published neurophysiological observations.

Acoustic Stimulation↗