A gene cadre orchestrates the normal development of sensory and non-sensory cells in the inner ear, segregating the cochlea with a distinct tonotopic sound frequency map, similar brain projection, and five vestibular end-organs. However, the role of genes driving the ear development is largely unknown. Here, we show double deletion of the Iroquois homeobox 3 and 5 transcription factors (Irx3/5 DKO) leads to the fusion of the saccule and the cochlear base. The overlying otoconia and tectorial membranes are absent in the Irx3/5 DKO inner ear, and the primary auditory neurons project fibers to both the saccule and cochlear hair cells. The central neuronal projections from the cochlear apex-base contour are not fully segregated into a dorsal and ventral innervation in the Irx3/5 DKO cochlear nucleus, obliterating the characteristic tonotopic auditory map. Additionally, Irx3/5 deletion reveals a pronounced cochlear-apex-vestibular "vestibular-cochlear" nerve (VCN) bilateral connection that is less noticeable in wild-type control mice. Moreover, the incomplete segregation of apex and base projections that expands fibers to connect with vestibular nuclei. The results suggest the mammalian cochlear apex is a derived lagena reminiscent of sarcopterygians. Thus, Irx3 and 5 are potential evolutionary branch-point genes necessary for balance-sound segregation, which fused into a saccule-cochlea organization.

• MeSH
• homeodoménové proteiny * genetika   metabolismus   MeSH
• kochlea * fyziologie   MeSH
• myši knockoutované * MeSH
• myši MeSH
• sakulus a utrikulus * fyziologie   MeSH
• sluchová dráha fyziologie   MeSH
• transkripční faktory * genetika   metabolismus   nedostatek   MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

Swept-sines provide a tool for fast and high-resolution measurement of evoked otoacoustic emissions. During the measurement, a response to swept-sine(s) is recorded by a probe placed in the ear canal. Otoacoustic emissions can then be extracted by various techniques, e.g., Fourier analysis, the heterodyne method, and the least-square-fitting (LSF) technique. This paper employs a technique originally proposed with exponential swept-sines, which allows for direct emission extraction from the measured intermodulation impulse response. It is shown here that the technique can be used to extract distortion-product otoacoustic emissions (DPOAEs) evoked with two simultaneous swept-sines. For proper extraction of the DPOAE phase, the technique employs previously proposed adjusted formulas for exponential swept-sines generating so-called synchronized swept-sines (SSSs). Here, the SSS technique is verified using responses derived from a numerical solution of a cochlear model and responses measured in human subjects. Although computationally much less demanding, the technique yields comparable results to those obtained by the LSF technique, which has been shown in the literature to be the most noise-robust among the emission extraction methods.

• MeSH
• Fourierova analýza MeSH
• kochlea * fyziologie   MeSH
• lidé MeSH
• otoakustické emise spontánní * fyziologie   MeSH
• zvukovod fyziologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

This review provides an up-to-date source of information on the primary auditory neurons or spiral ganglion neurons in the cochlea. These neurons transmit auditory information in the form of electric signals from sensory hair cells to the first auditory nuclei of the brain stem, the cochlear nuclei. Congenital and acquired neurosensory hearing loss affects millions of people worldwide. An increasing body of evidence suggest that the primary auditory neurons degenerate due to noise exposure and aging more readily than sensory cells, and thus, auditory neurons are a primary target for regenerative therapy. A better understanding of the development and function of these neurons is the ultimate goal for long-term maintenance, regeneration, and stem cell replacement therapy. In this review, we provide an overview of the key molecular factors responsible for the function and neurogenesis of the primary auditory neurons, as well as a brief introduction to stem cell research focused on the replacement and generation of auditory neurons.

• MeSH
• ganglion spirale embryologie   fyziologie   MeSH
• indukované pluripotentní kmenové buňky cytologie   MeSH
• kochlea embryologie   fyziologie   MeSH
• lidé MeSH
• mozkový kmen MeSH
• mutace MeSH
• myši MeSH
• neurogeneze MeSH
• neurony fyziologie   MeSH
• nucleus cochlearis embryologie   fyziologie   MeSH
• percepční nedoslýchavost patofyziologie   MeSH
• regenerativní lékařství metody   MeSH
• sekvence nukleotidů MeSH
• sluchové kmenové evokované potenciály MeSH
• vláskové buňky fyziologie   MeSH
• vnitřní ucho embryologie   fyziologie   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

The amplitudes of distortion-product otoacoustic emissions (DPOAEs) may abruptly decrease even though the stimulus level is relatively high. These notches observed in the DPOAE input/output functions or distortion-product grams have been hypothesized to be due to destructive interference between wavelets generated by distributed sources of the nonlinear-distortion component of DPOAEs. In this paper, simulations with a smooth cochlear model and its analytical solution support the hypothesis that destructive interference between individual wavelets may lead to the amplitude notches and explain the cause for onset and offset amplitude overshoots in the DPOAE signal measured for intensity pairs in the notches.

• MeSH
• akustická stimulace MeSH
• kochlea fyziologie   MeSH
• lidé MeSH
• otoakustické emise spontánní * MeSH
• teoretické modely * MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

• MeSH
• hipokampus anatomie a histologie   fyziologie   patofyziologie   MeSH
• kochlea anatomie a histologie   fyziologie   MeSH
• lidé MeSH
• motorické korové centrum anatomie a histologie   fyziologie   patofyziologie   MeSH
• mozeček anatomie a histologie   fyziologie   patofyziologie   MeSH
• nervus oculomotorius anatomie a histologie   fyziologie   MeSH
• nervus vestibulocochlearis anatomie a histologie   fyziologie   MeSH
• neuroplasticita fyziologie   MeSH
• senzorimotorický kortex anatomie a histologie   fyziologie   MeSH
• sluchové korové centrum anatomie a histologie   fyziologie   patofyziologie   MeSH
• somatosenzorické poruchy * diagnóza   etiologie   patofyziologie   MeSH
• statistika jako téma MeSH
• thalamus anatomie a histologie   fyziologie   patofyziologie   MeSH
• vestibulární aparát * anatomie a histologie   fyziologie   růst a vývoj   MeSH
• vestibulookulární reflex fyziologie   MeSH
• vnitřní ucho anatomie a histologie   fyziologie   MeSH
• závrať * diagnóza   etiologie   patofyziologie   MeSH
• zrakové korové centrum anatomie a histologie   fyziologie   patofyziologie   MeSH
• Check Tag
• lidé MeSH

There is a long-lasting question of how distortion products (DPs) arising from nonlinear amplification processes in the cochlea are transmitted from their generation sites to the stapes. Two hypotheses have been proposed: (1) the slow-wave hypothesis whereby transmission is via the transverse pressure difference across the cochlear partition and (2) the fast-wave hypothesis proposing transmission via longitudinal compression waves. Ren with co-workers have addressed this topic experimentally by measuring the spatial vibration pattern of the basilar membrane (BM) in response to two tones of frequency f(1) and f(2). They interpreted the observed negative phase slopes of the stationary BM vibrations at the cubic distortion frequency f(DP) = 2f(1) - f(2) as evidence for the fast-wave hypothesis. Here, using a physically based model, it is shown that their phase data is actually in accordance with the slow-wave hypothesis. The analysis is based on a frequency-domain formulation of the two-dimensional motion equation of a nonlinear hydrodynamic cochlea model. Application of the analysis to their experimental data suggests that the measurement sites of negative phase slope were located at or apical to the DP generation sites. Therefore, current experimental and theoretical evidence supports the slow-wave hypothesis. Nevertheless, the analysis does not allow rejection of the fast-wave hypothesis.

• MeSH
• biologické modely MeSH
• deformace percepce fyziologie   MeSH
• Fourierova analýza MeSH
• interferometrie metody   MeSH
• kochlea fyziologie   MeSH
• lasery MeSH
• lidé MeSH
• otoakustické emise spontánní fyziologie   MeSH
• vibrace MeSH
• vnímání výšky zvuku fyziologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH

The cubic component of the distortion product otoacoustic emission (DPOAE) in response to two tones of frequency f(1) and f(2) is generated by so-called primary- and secondary-source mechanisms in the cochlea. Interference between the resulting two source components can limit the usefulness of DPOAEs in assessing cochlear function. Although techniques are available for separating the source components, depending on the application, they can be either time-consuming or ineffective without a priori knowledge of optimal parameters. Here, we investigated, in humans, the possibility of separating the source components in the time-domain by sampling the onset and offset of the DPOAE-time signal at appropriate instants. Therefore, a DPOAE paradigm was developed in which the f(2) tone was periodically switched on during the continuous presence of the f(1) tone. F(2) was increased in 20-Hz steps from 1.5 to 2.5 kHz and the ratio f(2)/f(1) held constant at 1.2; measurements were made at six primary tone levels, ranging from L(2)=25 to 65 dB SPL. To investigate the possibility of separating the two sources by appropriate sampling, we developed an algorithm called onset-decomposition. The algorithm is based on the shape properties of DP-grams constructed from DPOAE responses at different time instants in the onset of the DPOAE signal. Thus, at each such time instant, the source components were extracted by time-windowing of the corresponding DP-gram. The time courses of the amplitude onsets of these separated primary- and secondary-source components provided evidence that the primary-source component attained its steady-state before the secondary-source component started to significantly influence the DPOAE by interference with the primary-source component. Consequently, in the final paradigm, the primary-source component is extracted by sampling the DPOAE signal at a single pre-defined time instant after the onset of the f(2) stimulus tone, before the secondary component begins to interfere. Based on the near-absence of interference maxima and minima in the DP-grams, the appropriate sampling instant was 8-10 ms for all frequencies and intensities in the stimulus set. Extracting the primary-source by onset sampling has the advantage that when individual source components for a given f(2) are to be investigated, there is no need to measure a DP-gram. In conclusion, it is shown that the technique can reliably and quickly separate the source components, making it an attractive paradigm for applications in basic research and clinical diagnosis. 2009 Elsevier B.V.

• MeSH
• akustická stimulace MeSH
• akustické impedanční testy MeSH
• algoritmy MeSH
• audiometrie čistými tóny MeSH
• biologické modely MeSH
• časové faktory MeSH
• dospělí MeSH
• Fourierova analýza MeSH
• kochlea fyziologie   MeSH
• lidé MeSH
• otoakustické emise spontánní MeSH
• počítačové zpracování signálu MeSH
• reakční čas MeSH
• reflex akustický MeSH
• reprodukovatelnost výsledků MeSH
• sluchová dráha fyziologie   MeSH
• sluchové kmenové evokované potenciály MeSH
• sluchový práh MeSH
• tlak MeSH
• zvuková spektrografie MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• práce podpořená grantem MeSH

The Fischer 344 rat strain has been frequently used as an animal model of rapid aging. The present study was aimed at evaluating the incidence of apoptotic cells in the inner ear of 20-24-month-old F344 rats and to correlate it with cochlear function using otoacoustic emissions. Staining with cresyl violet and the enzymatic labeling (terminal deoxynucleotidyl transferase, TdT) of fragmented DNA revealed large numbers of apoptotic cells in the marginal and basal layers of the stria vascularis and in adjacent cells of the spiral ligament. The amplitudes of distortion products otoacoustic emissions (DPOAEs), which reflect functional state of the outer hair cells, were significantly reduced or totally absent in these animals. In contrast to old F344 rats, no marked DPOAE amplitude reduction and smaller numbers of apoptotic cells were found in young 4-month-old F344 rats or in aged 24-28-month-old Long Evans rats. The accumulation of apoptotic cells, mainly in the basal layer of the stria vascularis and in adjacent cells of the spiral ligament, leads to a detachment of the stria vascularis from the spiral ligament and results in the impairment of outer hair cell function. This specific type of strial deterioration suggests that aged F344 rats can serve as an animal model of strial presbycusis.

• MeSH
• apoptóza MeSH
• buněčná smrt MeSH
• druhová specificita MeSH
• financování organizované MeSH
• fragmentace DNA MeSH
• imunohistochemie MeSH
• kochlea cytologie   fyziologie   růst a vývoj   MeSH
• krysa rodu rattus MeSH
• modely u zvířat MeSH
• potkani inbrední F344 fyziologie   růst a vývoj   MeSH
• sluch fyziologie   MeSH
• stárnutí fyziologie   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• zvířata MeSH

Hearing function in the Fischer 344 (F344) albino inbred strain of rats deteriorates with aging faster than in other strains, in spite of the small hair cell loss in old F344 animals [Popelar, J., Groh, D., Pelanova, J., Canlon, B., Syka, J., 2005. Age-related changes in cochlear and brainstem auditory function. Neurobiol. Aging, in press.]. This study was aimed at elucidating the structural changes in the inner ear of this rat strain during aging. Cochlear histopathology was examined in 20-24-month-old F344 rats and compared with that of young F344 rats (4 months) and of old rats of the Long-Evans (LE) strain. Hematoxylin/eosin staining in aged F344 rats showed degenerative changes in the organ of Corti, consisting of a damaged layer of marginal cells, reduced vascularization of the stria vascularis and a distorted tectorial membrane detached from the organ of Corti. Age-related changes in collagen distribution were observed with Masson's trichrome staining in the spiral ligament of old F344 rats. The results of immunohistochemical staining for type II collagen revealed a marked decrease in collagen fibers in the area connecting the spiral ligament and stria vascularis and a decrease in area IV fibrocytes in old F344 but not in LE rats. These findings may contribute to an explanation of the substantial hearing loss found in old F344 rats.

• MeSH
• azosloučeniny analýza   MeSH
• barvicí látky analýza   MeSH
• Cortiho orgán chemie   MeSH
• eosin analýza   MeSH
• fluorescenční barviva analýza   MeSH
• hematoxylin analýza   MeSH
• imunohistochemie metody   MeSH
• kochlea * fyziologie   chemie   MeSH
• kolagen typ II analýza   MeSH
• kolagen * analýza   MeSH
• krysa rodu rattus MeSH
• membrana tectoria chemie   MeSH
• methylová zeleň analýza   MeSH
• potkani inbrední F344 MeSH
• stárnutí * fyziologie   MeSH
• stria vascularis chemie   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• zvířata MeSH
• Publikační typ
• práce podpořená grantem MeSH

With the aim of characterizing the loss of high frequency hearing sensitivity in children, hearing thresholds and otoacoustic emissions were measured in a group of 126 normal hearing children and adolescents aged from 6 to 25 years. The subjects were divided into four 5-year age groups. Hearing thresholds over a range of 125 Hz-12.5 kHz were similar in all age groups, the average hearing threshold at 16 kHz was significantly elevated in the oldest age group. The response values of transiently evoked otoacoustic emissions (TEOAEs) significantly declined with age; the decline was negatively correlated with the hearing loss at 16 kHz. Significantly larger TEOAE responses and average distortion-product otoacoustic emission (DPOAE) values at 6.3 kHz were present in the youngest group in comparison with the other three older groups. Spontaneous otoacoustic emissions (SOAEs) were present in 70.8% of the children (in either one or both ears) with the greatest prevalence in the 11-20-year-old subjects. In the 21-25-year-old group, the hearing loss at 16 kHz was significantly smaller in ears with SOAEs than in ears without SOAEs. The results demonstrate that the increase in the high frequency hearing threshold at 16 kHz, which starts at ages over 20 years, is correlated with a decrease in the TEOAE responses at middle frequencies.

• MeSH
• akustické impedanční testy MeSH
• audiometrie čistými tóny MeSH
• dítě MeSH
• dospělí MeSH
• financování organizované MeSH
• kochlea fyziologie   MeSH
• lidé MeSH
• mladiství MeSH
• otoakustické emise spontánní fyziologie   MeSH
• otoskopie MeSH
• sluchový práh fyziologie   MeSH
• věkové faktory MeSH
• vnímání výšky zvuku fyziologie   MeSH
• vysokofrekvenční nedoslýchavost patofyziologie   MeSH
• Check Tag
• dítě MeSH
• dospělí MeSH
• lidé MeSH
• mladiství MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH