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T J Glattke

Publications and source records attributed to T J Glattke.

At least 19 recordsLinked to original sources
PubMed2002

The effect of noise bandwidth on the contralateral suppression of transient evoked otoacoustic emissions.

The purpose of this study was to determine whether the bandwidth or loudness of a contralateral stimulus is the most important factor in evoking suppression of transient evoked otoacoustic emissions (TEOAEs). TEOAEs were measured in both ears of 10 women in quiet and in the presence of one of three contralateral noise bands; narrow band (NB), wide band (WB) and equalized (EQ), all centered at 2000 Hz. The NB (100 Hz bandwidth) and WB (2200 Hz bandwidth) noises were presented at 60 dB SPL. The SPL of the EQ (100 Hz bandwidth) noise was adjusted such that it was equal in loudness to the WB noise as determined using a psychoacoustic procedure. Only the WB noise was associated with a significant reduction of TEOAE levels. It is believed that this effect occurred because the WB noise has greater effective energy representation across frequency on the basilar membrane as it may receive more gain from the action of the cochlear amplifier. Results of the present study indicate that noise bandwidth is the most important factor in the contralateral suppression of TEOAEs.

Acoustic Stimulation↗
PubMed1996

Distortion product otoacoustic emissions created through the interaction of spontaneous otoacoustic emissions and externally generated tones.

Spontaneous otoacoustic emissions (SOAEs) and external tones (XTs) were used as primaries f2 and f1, respectively (frequency of f2 > f1) to create 2f1--f2 distortion product otoacoustic emissions (DPOAEs). Amplitude and frequency of the SOAEs, XTs, and DPOAEs were recorded by placing a sensitive microphone in the ear canal and extracted using fast Fourier transform analysis. XTs were presented to ten ears at SOAE/f1 ratios between 1.08 and 1.22. XTs were incremented in 5-dB steps and ranged from levels equal to the initial SOAE amplitudes to levels at which the SOAEs and DPOAEs were suppressed into the noise floor. Results indicated that DPOAE amplitudes and SOAE suppression characteristics were idiosyncratic. Despite the variability, the following trends were noted: (1) at larger frequency ratios, DPOAE generation and SOAE suppression were associated with greater XT levels; (2) DPOAE growth functions were characterized by slopes less than 1 dB/dB, a maximum, rollover and disappearance into the noise floor with increasing XT levels; (3) maximum amplitude DPOAEs were observed at frequencies approximately one-half octave lower than the SOAE (f2); (4) the presence of DPOAEs was associated with SOAE suppression; (5) the most common SOAE frequency shift, in the presence of XT stimulation, was a shift to a higher frequency.

Acoustic Stimulation↗
PubMed1996

Detection of hearing loss in young children and adults using otoacoustic emissions.

Measures of transient evoked otoacoustic emission (TEOAE) reproducibility were obtained for 506 ears of 260 children and young adults. Frequency-specific and whole reproducibility data were obtained using ILO88 hardware and software (version 3.92), and were analyzed with respect to pure tone threshold and emmittance data for the same ears. The 2,000-Hz reproducibility score was the most efficient of all measurements (0.85-0.91) in separating normal and hearing-impaired ears, regardless of the frequencies at which the hearing loss occurred. TEOAE reproducibility measures may be very useful in screening for hearing loss in babies, leading to the earliest identification of children with hearing loss.

Acoustic Stimulation↗
PubMed1995

Conductive hearing loss in bighorn sheep.

In January 1993 we simulated a conductive hearing loss in three Mexican bighorn sheep (Ovis canadensis mexicana) by placing bone wax or saline solution in their ear canals. Our objective was to test whether lesions of the external auditory canal caused by psoroptic mites (Psoroptes ovis) may lead to conductive hearing loss in bighorn sheep. We assessed the effects of these manipulations using the auditory brainstem response test. Placing saline solution in the external auditory canal, which loads the tympanic membrane, had a more dramatic effect on the auditory brainstem response than did bone wax. We propose that decreased hearing sensitivity or alterations in resonance characteristics of the external auditory canal, due to psoroptic scabies lesions, may make bighorn sheep more susceptible to predation.

Animals↗
PubMed1994

A nicotinic-like receptor mediates suppression of distortion product otoacoustic emissions by contralateral sound.

The purpose of this investigation was to provide in vivo pharmacologic characterization of a cholinergic receptor mediating the suppressive effects of medial olivocochlear (MOC) efferent activation. MOC neurons were activated by contralateral sound and the resulting suppression of ipsilateral distortion product otoacoustic emissions (DPOAEs) was monitored before and after intracochlear perfusions of cholinergic antagonists. Results revealed a dose-dependent blockade of contralateral suppression of DPOAEs by a wide variety of nicotinic and muscarinic cholinergic receptor antagonists, as well as by non-traditional antagonists of cholinergic activity. The nicotinic antagonists, alpha-bungarotoxin, curare and kappa-bungarotoxin, and the glycine antagonist, strychnine, blocked contralateral suppression at nanomolar concentrations and demonstrated similar potencies. IC50 values were 2.38 x 10(-7), 2.79 x 10(-7), 3.81 x 10(-7) and 2.96 x 10(-7) M, respectively. These agents were followed in potency by the nicotinic antagonist, trimethaphan (1.75 x 10(-6) M), the M3 muscarinic antagonist, 4-DAMP (1.88 x 10(-6) M) and the GABAA antagonist, bicuculline (2.39 x 10(-6) M). Increasingly greater concentrations of the muscarinic antagonists, atropine (9.52 x 10(-6) M), AF-DX 116 (2.72 x 10(-5) M) and pirenzepine (8.24 x 10(-4) M) were necessary to block contralateral suppression of DPOAEs. The in vivo pharmacology of this putative outer hair cell cholinergic receptor suggests that it may be a member of the nicotinic family of receptors.

Acoustic Stimulation↗
PubMed1993

Contralateral sound suppresses distortion product otoacoustic emissions through cholinergic mechanisms.

Presentation of an acoustic signal to one ear can suppress sound-evoked activity recorded at the opposite ear. The suppression appears to be mediated by medial olivocochlear (MOC) efferent neurons synapsing with outer hair cells (OHCs) and acting through the MOC neurotransmitter, acetylcholine (ACh). The purpose of the present investigation was to study the suppression of distortion product otoacoustic emissions (DPOAEs) by contralateral sound and to examine whether the suppression could be blocked by known antagonists of olivocochlear (OC) efferent activity. Urethane-anesthetized guinea pigs were used. Perilymph spaces of ipsilateral cochleae were alternately perfused with artificial perilymph and drugs at 2.5 microliters/min for 10 min. After each period of perfusion, DPOAEs were measured before, during and after contralateral wideband noise (WBN) stimulation. Pre-perfusion, contralateral WBN attenuated the ipsilateral DPOAEs between 1-3 dB. This suppression was blocked reversibly by strychnine (10 microM), curare (10 microM) and atropine (20 microM), known antagonists of OC efferent activity. These results confirm the findings of Puel and Rebillard (1990) that contralateral WBN can suppress DPOAEs in anesthetized guinea pigs. Furthermore, results suggest that this efferent control of the cochlear mechanical response can either be mediated by both nicotinic and muscarinic cholinergic receptors, or that a single receptor with as yet undescribed structure and pharmacology mediates effects seen.

Acoustic Stimulation↗
PubMed1992

Intracochlear application of acetylcholine alters sound-induced mechanical events within the cochlear partition.

Activation of olivocochlear (OC) efferent fibers has been suggested to alter micromechanical events occurring within the cochlear partition, possibly through an effect of the efferent neurotransmitter (acetylcholine; ACh) on outer hair cells (OHCs). Based on the widely-accepted assumption that otoacoustic emissions reflect OHC activity, we investigated the in vivo influence of ACh on OHCs by studying alterations in emission amplitude with local ACh application. Distortion product otoacoustic emissions (DPOAEs) were measured in anesthetized guinea pigs before, during, and after intracochlear application of ACh (250 microM) with the cholinesterase inhibitor, eserine (20 microM). Perfusion of ACh/eserine was associated with a desensitizing reduction in DPOAE amplitude of approximately 4.4 dB. This reduction was intensity-dependent, with greater and more consistent reductions observed for DPOAEs elicited by low- than by moderate-intensity primaries. The response reduction was not seen during consecutive ACh perfusions performed without an intervening artificial perilymph wash, and was effectively blocked in the presence of pharmacologic antagonists of OC efferent activity (curare, 50 microM; strychnine, 50 microM). Finally, a similar alteration in DPOAE amplitude was never seen during perfusion of the control (artificial perilymph) solution alone. It is argued that these results support the hypothesis that OC efferent activation can alter sound-induced cochlear mechanical events.

Acetylcholine↗
PubMed1988

Reliability of spontaneous otoacoustic emission suppression tuning curve measures.

The purpose of this investigation was to study the reliability of spontaneous otoacoustic emission (SOAE) suppression tuning curve (STC) measurements. Two repetitions of an SOAE STC, using a 4-dB suppression criterion, were obtained from 5 subjects who exhibited stable SOAE level (SD less than or equal to 1.5 dB) and SOAE frequency (+/- 5 Hz). Analyses of variance revealed no significant difference between the SOAE STC trials (p greater than .05). The SOAE frequency was below the SOAE STC tip, which is similar to the relationship between the probe frequency and a simultaneously masked psychophysical tuning curve. The mean slope of the SOAE STC low-frequency segment was 53.7 dB/octave, whereas the mean slope of the SOAE STC high-frequency segment was 124.8 dB/octave. The mean low- to high-frequency slope ratio was 2.4. The mean Q10 value for the 5 subjects was 5.3. The SOAE STC low- and high-frequency slopes and Q10 were similar to psychophysical tuning curve data obtained in simultaneous masking and physiological tuning curve data.

Adult↗
PubMed1977

Electrophysiologic response audiometry: state of the art.

Electrophysiologic response audiometry (ERA) is based upon recording neuroelectric potentials from sites extending from the cochlea to the cortex. These recordings rely on the use of averaging computers to extricate desired neuroelectric responses from the ongoing background electrical activity of the human auditory system and brain. The different neuroelectric responses are distinguished by response latency, response waveform, and probable site of origin. Responses which occur within the latency range of 1 to 5 msec originate from the cochlea and auditory nerve. Responses in the 4- to 8-msec latency range have the brain stem as their origin. Responses with latencies from about 8 to 50 msec presumably arise from the upper brain stem and primary projection areas. Responses with a fast waveform include those with latencies between 1 and 50 msec. Slow wave responses from about 50 to 300 msec originate as a secondary discharge from the primary cortical projection areas and surrounding secondary and association areas. The longest latency potentials (300 msec) are slow shifts that appear to arise from the prefrontal and secondary or association areas of the cortex. These response classes are discussed in terms of their clinical utility for threshold estimation and diagnostic value.

Action Potentials↗
PubMed1976

Cochlear implants: technical and clinical implications.

Recent investigations using animal models and human subjects have helped to define the limits which are achievable in terms of information transfer with single-channel electrical stimulation of the auditory nerve. These studies are reviewed, and presented as a context for a description of the development of an implantable multiple-electrode multiplexing system which may provide control for several stimulus channels. While such a device may enable the stimulation of small segments of the auditory nerve independently, it does not contain any means of complex stimulus analysis and recording. This latter aspect of prosthesis development remains as the most formidable problem, from a technical viewpoint, that stands in the way of any significant progress.

Animals↗