scholarly journals Testing coherent reflection in chinchilla: Auditory-nerve responses predict stimulus-frequency emissions

2008 ◽  
Vol 124 (1) ◽  
pp. 381-395 ◽  
Author(s):  
Christopher A. Shera ◽  
Arnold Tubis ◽  
Carrick L. Talmadge
Keyword(s):  
Auditory Nerve ◽  
Stimulus Frequency ◽  
Coherent Reflection

scholarly journals Basilar membrane responses to two-tone and broadband stimuli

1992 ◽  
Vol 336 (1278) ◽  
pp. 307-315 ◽  
Keyword(s):  
Auditory Nerve ◽  
Basilar Membrane ◽  
Stimulus Frequency ◽  
Cell Receptor ◽  
Outer Hair Cells ◽  
Intermodulation Distortion ◽  
Mechanical Responses ◽  
Distortion Products ◽  
Cochlear Neurons ◽  
Rate Suppression

The responses to sound of mammalian cochlear neurons exhibit many nonlinearities, some of which (such as two-tone rate suppression and intermodulation distortion) are highly frequency specific, being strongly tuned to the characteristic frequency (CF) of the neuron. With the goal of establishing the cochlear origin of these auditory-nerve nonlinearities, mechanical responses to clicks and to pairs of tones were studied in relatively healthy chinchilla cochleae at a basal site of the basilar membrane with CF of 8-10 kHz. Responses were also obtained in cochleae in which hair cell receptor potentials were reduced by systemic furosemide injection. Vibrations were recorded using either the Mossbauer technique or laser Doppler-shift velocimetry. Responses to tone pairs contained intermodulation distortion products whose magnitudes as a function of stimulus frequency and intensity were com parable to those of distortion products in cochlear afferent responses. Responses to CF tones could be selectively suppressed by tones with frequency either higher or lower than CF; in most respects, mechanical two-tone suppression resembled rate suppression in cochlear afferents. Responses to clicks displayed a CF-specific compressive nonlinearity, similar to that present in responses to single tones, which could be profoundly and selectively reduced by furosemide. The present findings firmly support the hypothesis that all CF-specific nonlinearities present in the auditory nerve originate in analogous phenomena of basilar membrane vibration. However, because of their lability, it is almost certain that the mechanical nonlinearities themselves originate in outer hair cells.

Cochlear Sources and Otoacoustic Emissions

2010 ◽  
Vol 21 (03) ◽  
pp. 176-186 ◽  
Author(s):  
Tiffany A. Johnson
Keyword(s):  
Fine Structure ◽  
Otoacoustic Emissions ◽  
Stimulus Frequency ◽  
Normal Hearing ◽  
Clinical Applications ◽  
Clinical Test ◽  
Similar Amount ◽  
Distortion Product ◽  
Stimulus Parameters ◽  
Coherent Reflection

Current understanding suggests that there are two different mechanisms by which otoacoustic emissions (OAEs) are generated in the cochlea. These mechanisms include a nonlinear-distortion mechanism and a coherent-reflection mechanism. Distortion product OAEs (DPOAEs) are believed to include contributions from both mechanisms, while stimulus frequency OAEs (SFOAES), at least at low and moderate levels, are believed to be generated primarily by the coherent-reflection mechanism. In the case of DPOAEs, the interaction of the two mechanisms produces a series of alternating peaks and valleys in the response level when recorded in small frequency increments. This pattern of peaks and valleys typically is referred to as fine structure. There has been much speculation that the interaction of the two mechanisms and the resulting fine structure limits the clinical test performance of DPOAEs. There are few data to address this speculation. Here, we review the literature that describes the cochlear source mechanisms and their potential relationship to clinical applications. We then present results for preliminary data collected in a group of 10 normal-hearing subjects where we explore the influence of common approaches to setting DPOAE stimulus parameters on the resulting fine structure. These preliminary results suggest that, at the moderate stimulus levels used in clinical applications, each of the different stimulus parameters results in a similar amount of fine structure and, therefore, fine structure cannot be eliminated through manipulation of stimulus parameters. We also review the results of some preliminary efforts to identify stimulus parameters that can be used to record SFOAEs (OAEs generated by the reflection mechanism). The potential clinical applications of SFOAEs have received little attention in the literature. By identifying stimulus parameters producing robust responses in normal-hearing ears, it may be possible to more fully evaluate clinical applications of SFOAEs.

Delays of stimulus-frequency otoacoustic emissions and cochlear vibrations contradict the theory of coherent reflection filtering

2005 ◽  
Vol 118 (4) ◽  
pp. 2434-2443 ◽  
Author(s):  
Jonathan H. Siegel ◽  
Amanda J. Cerka ◽  
Alberto Recio-Spinoso ◽  
Andrei N. Temchin ◽  
Pim van Dijk ◽  
...  
Keyword(s):  
Otoacoustic Emissions ◽  
Stimulus Frequency ◽  
Coherent Reflection ◽  
Stimulus Frequency Otoacoustic Emissions

scholarly journals Salient features of otoacoustic emissions are common across tetrapod groups and suggest shared properties of generation mechanisms

2015 ◽  
Vol 112 (11) ◽  
pp. 3362-3367 ◽  
Author(s):  
Christopher Bergevin ◽  
Geoffrey A. Manley ◽  
Christine Köppl
Keyword(s):  
Otoacoustic Emissions ◽  
Stimulus Frequency ◽  
Barn Owl ◽  
Auditory Nerve Fiber ◽  
Tyto Alba ◽  
Integral Number ◽  
Green Anole ◽  
Coherent Reflection ◽  
Number Of Cycles ◽  
Generation Mechanisms

Otoacoustic emissions (OAEs) are faint sounds generated by healthy inner ears that provide a window into the study of auditory mechanics. All vertebrate classes exhibit OAEs to varying degrees, yet the biophysical origins are still not well understood. Here, we analyzed both spontaneous (SOAE) and stimulus-frequency (SFOAE) otoacoustic emissions from a bird (barn owl, Tyto alba) and a lizard (green anole, Anolis carolinensis). These species possess highly disparate macromorphologies of the inner ear relative to each other and to mammals, thereby allowing for novel insights into the biomechanical mechanisms underlying OAE generation. All ears exhibited robust OAE activity, and our chief observation was that SFOAE phase accumulation between adjacent SOAE peak frequencies clustered about an integral number of cycles. Being highly similar to published results from human ears, we argue that these data indicate a common underlying generator mechanism of OAEs across all vertebrates, despite the absence of morphological features thought essential to mammalian cochlear mechanics. We suggest that otoacoustic emissions originate from phase coherence in a system of coupled oscillators, which is consistent with the notion of “coherent reflection” but does not explicitly require a mammalian-type traveling wave. Furthermore, comparison between SFOAE delays and auditory nerve fiber responses for the barn owl strengthens the notion that most OAE delay can be attributed to tuning.

scholarly journals No Effect of Interstimulus Interval on Acoustic Reflex Thresholds

2019 ◽  
Vol 23 ◽  
pp. 233121651987416
Author(s):  
Hannah Guest ◽  
Kevin J. Munro ◽  
Samuel Couth ◽  
Rebecca E. Millman ◽  
Garreth Prendergast ◽  
...  
Keyword(s):  
Young People ◽  
Hair Cells ◽  
Auditory Nerve ◽  
Interstimulus Interval ◽  
Stimulus Frequency ◽  
Nerve Fibers ◽  
Acoustic Reflex ◽  
Clinically Normal ◽  
High Stimulus ◽  
Temporal Aspect

The acoustic reflex (AR), a longstanding component of the audiological test battery, has received renewed attention in the context of noise-induced cochlear synaptopathy—the destruction of synapses between inner hair cells and auditory nerve fibers. Noninvasive proxy measures of synaptopathy are widely sought, and AR thresholds (ARTs) correlate closely with synaptic survival in rodents. However, measurement in humans at high stimulus frequencies—likely important when testing for noise-induced pathology—can be challenging; reflexes at 4 kHz are frequently absent or occur only at high stimulus levels, even in young people with clinically normal audiograms. This phenomenon may partly reflect differences across stimulus frequency in the temporal characteristics of the response; later onset of the response, earlier onset of adaptation, and higher rate of adaptation have been observed at 4 kHz than at 1 kHz. One temporal aspect of the response that has received little attention is the interstimulus interval (ISI); inadequate duration of ISI might lead to incomplete recovery of the response between successive presentations and consequent response fatigue. This research aimed to test for effects of ISI on ARTs in normally hearing young humans, measured at 1 and 4 kHz. Contrary to our hypotheses, increasing ISIs from 2.5 to 8.5 s did not reduce ART level, nor raise ART reliability. Results confirm that clinically measured ARTs—including those at 4 kHz—can exhibit excellent reliability and that relatively short (2.5 s) ISIs are adequate for the measurement of sensitive and reliable ARTs.

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