Biomedical subjects

C Micheyl

Publications and source records attributed to C Micheyl.

44 records · Page 3Linked to original sources

PubMed1996

Involvement of the olivocochlear bundle in the detection of tones in noise.

To investigate the involvement of auditory efferents in hearing-in-noise in humans, olivocochlear bundle (OCB) functioning and detection-in-noise abilities were compared in 30 subjects. OCB function was assessed in terms of contralateral attenuation of evoked otoacoustic emissions (EOAE): i.e., the reduction in EOAE amplitude elicited by a 30-dB SL contralateral broadband noise. Correspondingly, the detection thresholds for 1- and 2-kHz tone pips embedded in 50-dB SPL broadband noise were measured in the same ear as the EOAEs, successively in the presence and in the absence of a 30-dB SL broadband noise in the opposite ear. The shifts in detection threshold induced by the contralateral stimulation could thus be compared to those in EOAEs. The results indicated significant statistical correlations between the contralateral attenuation of EOAEs and (1) the detection threshold of the 2-kHz signal and (2) the contralaterally induced shift in the 1- and 2-kHz thresholds. Furthermore, the correlation between contralaterally induced reduction of EOAE amplitude and contralaterally induced threshold shift was observed only in the group of subjects who had first performed the detection task in the presence of contralateral stimulation. These results, which suggest that OCB is involved in detection of tones in noise in humans, are discussed in relation to previous physiological and behavioral studies of OCB function.

Acoustic Stimulation↗

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↗

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

Neuronal correlates of perceptual amplitude-modulation detection.

The goal of the present paper is to relate the coding of amplitude modulation (AM) in the auditory pathway to the behavioral detection performance. To address this issue, the detectability of AM was estimated by modelling a single neuron located in the central nucleus of the inferior colliculus (IC). The computational model is based on cochlear nucleus responses and a coincidence detection mechanism. The model replicated the main feature of the neuronal AM transfer function, namely a bandpass function. The IC-unit model was initially tuned to a 200-Hz modulation frequency. A single neurometric function for AM detection at this modulation frequency was generated using a 2-interval, 2-alternative forced-choice paradigm. On each trial of the experiments, AM was taken to be correctly detected by the model if the number of spikes in response to the modulated signal exceeded the number of spikes in an otherwise identical interval that contained an unmodulated signal. Psychometric functions for 4 human subjects were also measured under the same stimulus conditions. Comparison of the simulated neurometric and psychometric functions suggested that there was sufficient information in the rate response of an IC neuron well-tuned in the modulation-frequency domain to support behavioral detection performance.

Acoustic Stimulation↗

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↗

PubMed1994

Interrelations between psychoacoustical tuning curves and spontaneous and evoked otoacoustic emissions.

With the hypothesis that cochlear active mechanisms are the origin of otoacoustic emissions (OAEs) and of the high frequency selectivity exhibited by the ear, psychoacoustical tuning curves (PTCs), transiently evoked otoacoustic emissions (TEOAEs), and spontaneous otoacoustic emissions (SOAEs) have been examined in 50 normal hearing subjects. Using a clinical simplified method, PTCs were successively assessed at three frequencies--1, 2 and 4 kHz--in each subject. The results showed the existence of significant differences in the quality of tuning (Q10dB) of the PTCs between, first, subjects having SOAEs and subjects having no SOAEs (Student's t-test; p < 0.05; df = 35) and, second, subjects having large TEOAEs and subjects having small TEOAEs (Student's t-test; p < 0.05; df = 14). Nevertheless, these significant differences did not appear for all the frequencies studied: the frequency selective relationship between PTCs and OAEs mainly involved the 2 kHz zone. Such results are discussed according to the specificities of the clinical method used for PTC measurement as well as to the spectral characteristics of OAEs.

Acoustic Stimulation↗

PubMedDate not supplied

Effect of signal duration on categorical loudness scaling in normal and in hearing-impaired listeners.

The present study sought to determine whether the duration of white-noise bursts affects their loudness category rating in the same way for hearing-impaired as for normally-hearing subjects. Twelve normally-hearing and 12 hearing-impaired subjects took part. Categorical loudness growth functions were obtained for 16.25 ms, 32.5 ms, 75 ms, 150 ms and 300 ms white noise bursts. Temporal integration of loudness was defined as the intensity difference needed for stimuli of different durations to result in identical category ratings. In normally-hearing subjects, temporal integration of loudness occurred mainly with the short-duration (16.25 ms and 32.5 ms) stimuli, whereas it was found with almost every stimulus duration in hearing-impaired subjects. In other words, temporal integration of loudness between 16.25 ms and 300 ms stimulus duration was greater in hearing-impaired listeners and there was a difference between normal and hearing-impaired subjects regarding change in loudness perception with stimulus duration. Consequently, the use of fixed-duration stimuli hinders loudness normalization.

Adolescent↗

PubMedDate not supplied

Contralateral auditory stimulation and otoacoustic emissions: a review of basic data in humans.

The influence of contralateral auditory stimulation on otoacoustic emissions (OAE), spontaneous OAE, evoked OAE and acoustic distortion products, can be summarized as follows: (1) alteration (mainly a decrease) of OAE amplitude; (2) alteration of response spectrum (upward shift frequency of SOAE); (3) alteration of phase; (4) effect dependent on intensity of contralateral stimulation; (5) effect inversely dependent on intensity of ipsilateral stimulation; (6) frequency specificity of the suppressive effect. Involvement of the medial olivocochlear bundle is highly probable but one cannot exclude a double pathway including also the acoustic reflex.

Acoustic Stimulation↗