Audiology by Alexandros G. Sfakianakis: 10/08/16

Publication date: November 2016
Source:Hearing Research, Volume 341
Author(s): Clemens Honeder, Chengjing Zhu, Hanna Schöpper, Julia Clara Gausterer, Manuel Walter, Lukas David Landegger, Nodir Saidov, Dominik Riss, Roberto Plasenzotti, Franz Gabor, Christoph Arnoldner
It has been shown that glucocorticoids reduce the hearing threshold shifts associated with cochlear implantation. Previous studies evaluated the administration of glucocorticoids immediately before surgery or the repeated pre- or perioperative systemic application of glucocorticoids. The aim of this study was to evaluate the effects of a sustained release dexamethasone hydrogel in hearing preservation cochlear implantation. To address this issue, a guinea pig model of cochlear implantation was used. 30 normal hearing pigmented guinea pigs were randomized into a group receiving a single dose of a dexamethasone/poloxamer407 hydrogel one day prior to surgery, a second group receiving the hydrogel seven days prior to surgery and a control group. A silicone cochlear implant electrode designed for the use in guinea pigs was inserted to a depth of 5 mm through a cochleostomy. Compound action potentials of the auditory nerve (frequency range 0.5–32 kHz) were measured preoperatively, directly postoperatively and on postoperative days 3, 7, 14, 21 and 28. Following the last audiometry, temporal bones were harvested and histologically evaluated.Dexamethasone hydrogel application one day prior to surgery resulted in significantly reduced hearing threshold shifts at low, middle and high frequencies measured at postoperative day 28 (p < 0.05). Application of the hydrogel seven days prior to surgery did not show such an effect. Dexamethasone application one day prior to surgery resulted in increased outer hair cell counts in the cochlear apex and in reduced spiral ganglion cell counts in the basal and middle turn of the cochlea, a finding that was associated with a higher rate of electrode translocation in this group.In this study, we were able to demonstrate functional benefits of a single preoperative intratympanic application of a sustained release dexamethasone hydrogel in a guinea pig model of cochlear implantation.

from #Audiology via ola Kala on Inoreader http://ift.tt/2bbjsrI
via IFTTT

Across-site patterns of electrically evoked compound action potential amplitude-growth functions in multichannel cochlear implant recipients and the effects of the interphase gap

Publication date: November 2016
Source:Hearing Research, Volume 341
Author(s): Kara C. Schvartz-Leyzac, Bryan E. Pfingst
Electrically evoked compound action potential (ECAP) measures of peak amplitude, and amplitude-growth function (AGF) slope have been shown to reflect characteristics of cochlear health (primarily spiral ganglion density) in anesthetized cochlear-implanted guinea pigs. Likewise, the effect of increasing the interphase gap (IPG) in each of these measures also reflects SGN density in the implanted guinea pig. Based on these findings, we hypothesize that suprathreshold ECAP measures, and also how they change as the IPG is increased, have the potential to be clinically applicable in human subjects. However, further work is first needed in order to determine the characteristics of these measures in humans who use cochlear implants.The current study examined across-site patterns of suprathreshold ECAP measures in 10 bilaterally-implanted, adult cochlear implant users. Results showed that both peak amplitude and slope of the AGF varied significantly from electrode to electrode in ear-specific patterns across the subjects' electrode arrays. As expected, increasing the IPG on average increased the peak amplitude and slope. Across ears, there was a significant, negative correlation between the slope of the ECAP AGF and the duration of hearing loss. Across-site patterns of ECAP peak amplitude and AGF slopes were also compared with common ground impedance values and significant correlations were observed in some cases, depending on the subject and condition. The results of this study, coupled with previous studies in animals, suggest that it is feasible to measure the change in suprathreshold ECAP measures as the IPG increases on most electrodes. Further work is needed to investigate the relationship between these measures and cochlear implant outcomes, and determine how these measures might be used when programming a cochlear-implant processor.

from #Audiology via ola Kala on Inoreader http://ift.tt/2bkPf6w
via IFTTT

Low-frequency bias tone suppression of auditory-nerve responses to low-level clicks and tones

Publication date: November 2016
Source:Hearing Research, Volume 341
Author(s): Hui Nam, John J. Guinan
We used low-frequency “bias” tones (BT's) to explore whether click and tone responses are affected in the same way by cochlear active processes. In nonlinear systems the responses to clicks are not always simply related to the responses to tones. Cochlear amplifier gain depends on the incremental slope of the outer-hair-cell (OHC) stereocilia mechano-electric transduction (MET) function. BTs transiently change the operating-point of OHC MET channels and can suppress cochlear-amplifier gain by pushing OHC METs into low-slope saturation regions. BT effects on single auditory-nerve (AN) fibers have been studied on tone responses but not on click responses. We recorded from AN fibers in anesthetized cats and compared tone and click responses using 50 Hz BTs at 70–120 dB SPL to manipulate OHC stereocilia position. BTs can also excite and thereby obscure the BT suppression. We measured AN-fiber response synchrony to BTs alone so that we could exclude suppression measurements when the BT synchrony might obscure the suppression. BT suppression of low-level tone and click responses followed the traditional pattern of twice-a-BT-cycle suppression with more suppression at one phase than the other. The major suppression phases of most fibers were tightly grouped with little difference between click and tone suppressions, which is consistent with low-level click and tone responses being amplified in the same way. The data are also consistent with the operating point of the OHC MET function varying smoothly from symmetric in the base to offset in the apex, and, in contrast, with the IHC MET function being offset throughout the cochlea. As previously reported, bias-tones presented alone excited AN fibers at one or more phases, a phenomena termed “peak splitting” with most BT excitation phases ∼¼ cycle before or after the major suppression phase. We explain peak splitting as being due to distortion in multiple fluid drives to inner-hair-cell stereocilia.

from #Audiology via ola Kala on Inoreader http://ift.tt/2c2VBrR
via IFTTT

Differences in synaptic and intrinsic properties result in topographic heterogeneity of temporal processing of neurons within the inferior colliculus

Publication date: November 2016
Source:Hearing Research, Volume 341
Author(s): Lina Yassin, Michael Pecka, Jasmin Kajopoulos, Helge Gleiss, Lu Li, Christian Leibold, Felix Felmy
The identification and characterization of organization principals is essential for the understanding of neural function of brain areas. The inferior colliculus (IC) represents a midbrain nexus involved in numerous aspects of auditory processing. Likewise, neurons throughout the IC are tuned to a diverse range of specific stimulus features. Yet beyond a topographic arrangement of the cochlea-inherited frequency tuning, the functional organization of the IC is not well understood. Particularly, a common principle that links the diverse tuning characteristics is unknown. Here we used in vitro patch clamp recordings combined with laser-uncaging, and in vivo single cell recordings to study the spatial and functional organization principles of the central IC. We identified a topographic bias of ascending synaptic input timing that is balanced between inhibition and excitation and co-varies with in vivo first–spike latency. This bias was paralleled post-synaptically by differences in biophysical membrane properties and firing patterns, with integrating neurons predominantly found in the dorso-medial part, and coincidence-detector neurons biased to the ventro-lateral IC. Importantly, these cellular and network features translated into distinct temporal processing capabilities irrespectively of the neurons' characteristic frequency. Our data therefore imply that heterogeneity of synaptic inputs, intrinsic properties and temporal processing are functional principles that underlie the spatial organization of the central IC.

from #Audiology via ola Kala on Inoreader http://ift.tt/2bKC2Z7
via IFTTT

Endothelin-1 mediated induction of extracellular matrix genes in strial marginal cells underlies strial pathology in Alport mice

Publication date: November 2016
Source:Hearing Research, Volume 341
Author(s): Daniel T. Meehan, Duane Delimont, Brianna Dufek, Marisa Zallocchi, Grady Phillips, Michael Anne Gratton, Dominic Cosgrove
Alport syndrome, a type IV collagen disorder, manifests as glomerular disease associated with hearing loss with thickening of the glomerular and strial capillary basement membranes (SCBMs). We have identified a role for endothelin-1 (ET-1) activation of endothelin A receptors (ETARs) in glomerular pathogenesis. Here we explore whether ET-1 plays a role in strial pathology. Wild type (WT) and Alport mice were treated with the ETAR antagonist, sitaxentan. The stria vascularis was analyzed for SCBM thickness and for extracellular matrix (ECM) proteins. Additional WT and Alport mice were exposed to noise or hypoxia and the stria analyzed for hypoxia-related and ECM genes. A strial marginal cell line cultured under hypoxic conditions, or stimulated with ET-1 was analyzed for expression of hypoxia-related and ECM transcripts. Noise exposure resulted in significantly elevated ABR thresholds in Alport mice relative to wild type littermates. Alport stria showed elevated expression of collagen α1(IV), laminin α2, and laminin α5 proteins relative to WT. SCBM thickening and elevated ECM protein expression was ameliorated by ETAR blockade. Stria from normoxic Alport mice and hypoxic WT mice showed upregulation of hypoxia-related, ECM, and ET-1 transcripts. Both ET-1 stimulation and hypoxia up-regulated ECM transcripts in cultured marginal cells. We conclude that ET-1 mediated activation of ETARs on strial marginal cells results in elevated expression of ECM genes and thickening of the SCBMs in Alport mice. SCBM thickening results in hypoxic stress further elevating ECM and ET-1 gene expression, exacerbating strial pathology.

from #Audiology via ola Kala on Inoreader http://ift.tt/2baOsIw
via IFTTT

The contribution of inferior colliculus activity to the auditory brainstem response (ABR) in mice

Publication date: November 2016
Source:Hearing Research, Volume 341
Author(s): Rüdiger Land, Alice Burghard, Andrej Kral
In mice, the auditory brainstem response (ABR) is frequently used to assess hearing status in transgenic hearing models. The diagnostic value of the ABR depends on knowledge about the anatomical sources of its characteristic waves. Here, we studied the contribution of the inferior colliculus (IC) to the click-evoked scalp ABR in mice. We demonstrate a non-invasive correlate of the IC response that can be measured in the scalp ABR as a slow positive wave P0 with peak latency 7–8 ms when recorded with adequate band-pass filtering. Wave P0 showed close correspondence in latency, magnitude and shape with the sustained part of evoked spiking activity and local field potentials (LFP) in the central nucleus of the IC. In addition, the onset peaks of the IC response were related temporally to ABR wave V and to some extent to wave IV. This relation was further supported by depth-dependent modulation of the shape of ABR wave IV and V within the IC suggesting generation within or in close vicinity to the IC. In conclusion, the slow ABR wave P0 in the scalp ABR may represent a complementary non-invasive marker for IC activity in the mouse. Further, the latency of synchronized click-evoked activity in the IC supports the view that IC contributes to ABR wave V, and possibly also to ABR wave IV.

from #Audiology via ola Kala on Inoreader http://ift.tt/2bwzo4m
via IFTTT

The effects of aging and sex on detection of ultrasonic vocalizations by adult CBA/CaJ mice (Mus musculus)

Publication date: November 2016
Source:Hearing Research, Volume 341
Author(s): Anastasiya Kobrina, Micheal L. Dent
Mice are frequently used as animal models for human hearing research, yet their auditory capabilities have not been fully explored. Previous studies have established auditory threshold sensitivities for pure tone stimuli in CBA/CaJ mice using ABR and behavioral methodologies. Little is known about how they perceive their own ultrasonic vocalizations (USVs), and nothing is known about how aging influences this perception. The aim of the present study was to establish auditory threshold sensitivity for several USV types, as well as to track these thresholds across the mouse's lifespan. In order to determine how well mice detect these complex communication stimuli, several CBA/CaJ mice were trained and tested at various ages on a detection task using operant conditioning procedures. Results showed that mice were able to detect USVs into old age. Not surprisingly, thresholds differed for the different USV types. Male mice suffered greater hearing loss than females for all calls but not for 42 kHz tones. In conclusion, the results highlight the importance of studying complex signals across the lifespan.

from #Audiology via ola Kala on Inoreader http://ift.tt/2bOlgH8
via IFTTT

A fast, stochastic, and adaptive model of auditory nerve responses to cochlear implant stimulation

Publication date: November 2016
Source:Hearing Research, Volume 341
Author(s): M.J. van Gendt, J.J. Briaire, R.K. Kalkman, J.H.M. Frijns
Cochlear implants (CIs) rehabilitate hearing impairment through direct electrical stimulation of the auditory nerve. New stimulation strategies can be evaluated using computational models. In this study, a computationally efficient model that accurately predicts auditory nerve responses to CI pulse train input was developed. A three-dimensional volume conduction and active nerve model developed at Leiden University Medical Center was extended with stochasticity, adaptation, and accommodation. This complete model includes spatial and temporal characteristics of both the cochlea and the auditory nerve. The model was validated by comparison with experimentally measured single fiber action potential responses to pulse trains published in the literature. The effects of pulse rate and pulse amplitude on spiking patterns were investigated. The modeled neural responses to CI stimulation were very similar to the single fiber action potential measurements in animal experiments. The model's responses to pulse train stimulation with respect to spatial location were also investigated. Adaptation was stronger at the borders of the stimulated area than in the center. By combining spatial details with long-term temporal components and a broad implementation of stochasticity a comprehensive model was developed that was validated for long duration electric stimulation of a wide range of pulse rates and amplitudes. The model can be used to evaluate auditory nerve responses to cochlear implant sound coding strategies.

from #Audiology via ola Kala on Inoreader http://ift.tt/2cfGXx5
via IFTTT

A tri-coil bellows-type round window transducer with improved frequency characteristics for middle-ear implants

Publication date: November 2016
Source:Hearing Research, Volume 341
Author(s): Dong Ho Shin, Ki Woong Seong, Sunil Puria, Kyu-Yup Lee, Jin-Ho Cho
A number of methods to drive the round window (RW) using a floating mass transducer (FMT) have been reported. This method has attracted attention because the FMT is relatively easy to implant in the RW niche. However, the use of an FMT to drive the RW has been proven to produce low outputs at frequencies below approximately 1 kHz. In this study, a new tri-coil bellows-type transducer (TCBT), which has excellent low frequency output and is easy to implant, is proposed. To design the frequency characteristics of the TCBT, mechanical and electrical simulations were performed, and then a comparative analysis was conducted between a floating mass type transducer (like the FMT) and a fixed type transducer (like the TCBT). The features of the proposed TCBT are as follows. First, the TCBT's housing is fixed to the RW niche so that it does not vibrate. Second, the internal end of a tiny bellows is connected to a vibrating three-pole permanent magnet located within three field coils. Finally, the rim of the bellows bottom is attached to the end of the housing that hermetically encloses the three field coils. In this design, the only vibrating element is the bellows itself, which efficiently drives the RW membrane. To evaluate the characteristics of this newly developed TCBT, the transducer was installed in the RW niche of temporal bones and the velocity of the stapes was measured using a laser Doppler vibrometer. The experimental results indicate that the TCBT can produce 100, 111, and 129 dB SPL equivalent pressure outputs at below 1 kHz, 1–3 kHz, and above 3 kHz, respectively. Thus, the TCBT with one side coupled to the RW via a bellows will be easy to implant and offer better performance than an FMT.

from #Audiology via ola Kala on Inoreader http://ift.tt/2c7r6mW
via IFTTT

Modelling the effect of round window stiffness on residual hearing after cochlear implantation

Publication date: November 2016
Source:Hearing Research, Volume 341
Author(s): Stephen J. Elliott, Guangjian Ni, Carl A. Verschuur
Preservation of residual hearing after cochlear implantation is now considered an important goal of surgery. However, studies indicate an average post-operative hearing loss of around 20 dB at low frequencies. One factor which may contribute to post-operative hearing loss, but which has received little attention in the literature to date, is the increased stiffness of the round window, due to the physical presence of the cochlear implant, and to its subsequent thickening or to bone growth around it. A finite element model was used to estimate that there is approximately a 100-fold increase in the round window stiffness due to a cochlear implant passing through it. A lumped element model was then developed to study the effects of this change in stiffness on the acoustic response of the cochlea. As the round window stiffness increases, the effects of the cochlear and vestibular aqueducts become more important. An increase of round window stiffness by a factor of 10 is predicted to have little effect on residual hearing, but increasing this stiffness by a factor of 100 reduces the acoustic sensitivity of the cochlea by about 20 dB, below 1 kHz, in reasonable agreement with the observed loss in residual hearing after implantation. It is also shown that the effect of this stiffening could be reduced by incorporating a small gas bubble within the cochlear implant.

from #Audiology via ola Kala on Inoreader http://ift.tt/2bBjABz
via IFTTT

Speech perception adjusts to stable spectrotemporal properties of the listening environment

Publication date: November 2016
Source:Hearing Research, Volume 341
Author(s): Christian E. Stilp, Paul W. Anderson, Ashley A. Assgari, Gregory M. Ellis, Pavel Zahorik
When perceiving speech, listeners compensate for reverberation and stable spectral peaks in the speech signal. Despite natural listening conditions usually adding both reverberation and spectral coloration, these processes have only been studied separately. Reverberation smears spectral peaks across time, which is predicted to increase listeners' compensation for these peaks. This prediction was tested using sentences presented with or without a simulated reverberant sound field. All sentences had a stable spectral peak (added by amplifying frequencies matching the second formant frequency [F2] in the target vowel) before a test vowel varying from /i/ to /u/ in F2 and spectral envelope (tilt). In Experiment 1, listeners demonstrated increased compensation (larger decrease in F2 weights and larger increase in spectral tilt weights for identifying the target vowel) in reverberant speech than in nonreverberant speech. In Experiment 2, increased compensation was shown not to be due to reverberation tails. In Experiment 3, adding a pure tone to nonreverberant speech at the target vowel's F2 frequency increased compensation, revealing that these effects are not specific to reverberation. Results suggest that perceptual adjustment to stable spectral peaks in the listening environment is not affected by their source or cause.

from #Audiology via ola Kala on Inoreader http://ift.tt/2con6Pm
via IFTTT

The effect of distraction on change detection in crowded acoustic scenes

Publication date: November 2016
Source:Hearing Research, Volume 341
Author(s): Theofilos Petsas, Jemma Harrison, Makio Kashino, Shigeto Furukawa, Maria Chait
In this series of behavioural experiments we investigated the effect of distraction on the maintenance of acoustic scene information in short-term memory. Stimuli are artificial acoustic ‘scenes’ composed of several (up to twelve) concurrent tone-pip streams (‘sources’). A gap (1000 ms) is inserted partway through the ‘scene’; Changes in the form of an appearance of a new source or disappearance of an existing source, occur after the gap in 50% of the trials. Listeners were instructed to monitor the unfolding ‘soundscapes’ for these events. Distraction was measured by presenting distractor stimuli during the gap. Experiments 1 and 2 used a dual task design where listeners were required to perform a task with varying attentional demands (‘High Demand’ vs. ‘Low Demand’) on brief auditory (Experiment 1a) or visual (Experiment 1b) signals presented during the gap. Experiments 2 and 3 required participants to ignore distractor sounds and focus on the change detection task. Our results demonstrate that the maintenance of scene information in short-term memory is influenced by the availability of attentional and/or processing resources during the gap, and that this dependence appears to be modality specific. We also show that these processes are susceptible to bottom up driven distraction even in situations when the distractors are not novel, but occur on each trial. Change detection performance is systematically linked with the, independently determined, perceptual salience of the distractor sound. The findings also demonstrate that the present task may be a useful objective means for determining relative perceptual salience.

from #Audiology via ola Kala on Inoreader http://ift.tt/2c7r8v7
via IFTTT

Dopaminergic projections of the subparafascicular thalamic nucleus to the auditory brainstem

Publication date: November 2016
Source:Hearing Research, Volume 341
Author(s): Alexander A. Nevue, Richard A. Felix, Christine V. Portfors
Neuromodulators can alter the response properties of sensory neurons, including those in the auditory system. Dopamine, which plays a major role in reward and movement, has been shown to alter neural responses in the auditory brainstem and midbrain. Recently we identified the subparafascicular thalamic nucleus (SPF), part of the A11 dopaminergic cell group, as the source of dopamine to the inferior colliculus (IC). The superior olivary complex (SOC) is also a likely target of dopaminergic projections from the SPF because it receives projections from the SPF and contains fibers and terminals immunoreactive for tyrosine hydroxylase, the rate limiting enzyme in dopamine synthesis. However, it is unknown if the projections from the SPF to SOC are dopaminergic, and if single neurons in the SPF project to both the IC and SOC. Using anterograde tracing combined with fluorescent immunohistochemistry, we found that the SPF sends dopaminergic projections to the superior paraolivary nucleus and the medial nucleus of the trapezoid body, but not the lateral superior olive. We confirmed these projections using a retrograde tracer. By making dual retrograde deposits in the IC and SOC, we found that individual dopaminergic cells innervate both the IC and SOC. These results suggest dopaminergic innervation, likely released in a context dependent manner, occurs at multiple levels of the auditory pathway.

Graphical abstract

from #Audiology via ola Kala on Inoreader http://ift.tt/2cOhC0O
via IFTTT

Time course and frequency specificity of sub-cortical plasticity in adults following acute unilateral deprivation

Publication date: November 2016
Source:Hearing Research, Volume 341
Author(s): Hannah Brotherton, Christopher J. Plack, Roland Schaette, Kevin J. Munro
Auditory deprivation and stimulation can change the threshold of the acoustic reflex, but the mechanisms underlying these changes remain largely unknown. In order to elucidate the mechanism, we sought to characterize the time-course as well as the frequency specificity of changes in acoustic reflex thresholds (ARTs). In addition, we compared ipsilateral and contralateral measurements because the pattern of findings may shed light on the anatomical location of the change in neural gain. Twenty-four normal-hearing adults wore an earplug continuously in one ear for six days. We measured ipsilateral and contralateral ARTs in both ears on six occasions (baseline, after 2, 4 and 6 days of earplug use, and 4 and 24 h after earplug removal), using pure tones at 0.5, 1, 2 and 4 kHz and a broadband noise stimulus, and an experimenter-blinded design. We found that ipsi- as well as contralateral ARTs were obtained at a lower sound pressure level after earplug use, but only when the reflex was elicited by stimulating the treatment ear. Changes in contralateral ARTs were not the same as changes in ipsilateral ARTs when the stimulus was presented to the control ear. Changes in ARTs were present after 2 days of earplug use, and reached statistical significance after 4 days, when the ipsilateral and contralateral ARTs were measured in the treatment ear. The greatest changes in ARTs occurred at 2 and 4 kHz, the frequencies most attenuated by the earplug. After removal of the earplug, ARTs started to return to baseline relatively quickly, and were not significantly different from baseline by 4–24 h. There was a trend for the recovery to occur quicker than the onset. The changes in ARTs are consistent with a frequency-specific gain control mechanism operating around the level of the ventral cochlear nucleus in the treatment ear, on a time scale of hours to days. These findings, specifically the time course of change, could be applicable to other sensory systems, which have also shown evidence of a neural gain control mechanism.

from #Audiology via ola Kala on Inoreader http://ift.tt/2cziOmr
via IFTTT

Hearing sensitivity differs between zebrafish lines used in auditory research

Publication date: November 2016
Source:Hearing Research, Volume 341
Author(s): J. David Monroe, Dustin P. Manning, Phillip M. Uribe, Ashwin Bhandiwad, Joseph A. Sisneros, Michael E. Smith, Allison B. Coffin
Zebrafish are increasingly used in auditory studies, in part due to the development of several transgenic lines that express hair cell-specific fluorescent proteins. However, it is largely unknown how transgene expression influences auditory phenotype. We previously observed reduced auditory sensitivity in adult Brn3c:mGFP transgenic zebrafish, which express membrane-bound green fluorescent protein (GFP) in sensory hair cells. Here, we examine the auditory sensitivity of zebrafish from multiple transgenic and background strains. We recorded auditory evoked potentials in adult animals and observed significantly higher auditory thresholds in three lines that express hair cell-specific GFP. There was no obvious correlation between hair cell density and auditory thresholds, suggesting that reduced sensitivity was not due to a reduction in hair cell density. FM1-43 uptake was reduced in Brn3c:mGFP fish but not in other lines, suggesting that a mechanotransduction defect may be responsible for the auditory phenotype in Brn3c animals, but that alternate mechanisms underlie the increased AEP thresholds in other lines. We found reduced prepulse inhibition (a measure of auditory-evoked behavior) in larval Brn3c animals, suggesting that auditory defects develop early in this line. We also found significant differences in auditory sensitivity between adults of different background strains, akin to strain differences observed in mouse models of auditory function. Our results suggest that researchers should exercise caution when selecting an appropriate zebrafish transgenic or background strain for auditory studies.

from #Audiology via ola Kala on Inoreader http://ift.tt/2cgShwG
via IFTTT

Study of tonotopic brain changes with functional MRI and FDG-PET in a patient with unilateral objective cochlear tinnitus

Publication date: November 2016
Source:Hearing Research, Volume 341
Author(s): A.-C. Guinchard, N. Ghazaleh, M. Saenz, E. Fornari, J.O. Prior, P. Maeder, S. Adib, R. Maire
We studied possible brain changes with functional MRI (fMRI) and fluorodeoxyglucose positron emission tomography (FDG-PET) in a patient with a rare, high-intensity “objective tinnitus” (high-level SOAEs) in the left ear of 10 years duration, with no associated hearing loss. This is the first case of objective cochlear tinnitus to be investigated with functional neuroimaging.The objective cochlear tinnitus was measured by Spontaneous Otoacoustic Emissions (SOAE) equipment (frequency 9689 Hz, intensity 57 dB SPL) and is clearly audible to anyone standing near the patient. Functional modifications in primary auditory areas and other brain regions were evaluated using 3T and 7T fMRI and FDG-PET.In the fMRI evaluations, a saturation of the auditory cortex at the tinnitus frequency was observed, but the global cortical tonotopic organization remained intact when compared to the results of fMRI of healthy subjects. The FDG-PET showed no evidence of an increase or decrease of activity in the auditory cortices or in the limbic system as compared to normal subjects.In this patient with high-intensity objective cochlear tinnitus, fMRI and FDG-PET showed no significant brain reorganization in auditory areas and/or in the limbic system, as reported in the literature in patients with chronic subjective tinnitus.

from #Audiology via ola Kala on Inoreader http://ift.tt/2ckbmsQ
via IFTTT

Perilymph pharmacokinetics of locally-applied gentamicin in the guinea pig

Publication date: Available online 8 October 2016
Source:Hearing Research
Author(s): A.N. Salt, J.J. Hartsock, R.M. Gill, E. King, F.B. Kraus, S.K. Plontke
Intratympanic gentamicin therapy is widely used clinically to suppress the vestibular symptoms of Meniere’s disease. Dosing in humans was empirically established and we still know remarkably little about where gentamicin enters the inner ear, where it reaches in the inner ear and what time course it follows after local applications. In this study, gentamicin was applied to the round window niche as a 20 μL bolus of 40 mg/ml solution. Ten 2 μL samples of perilymph were collected sequentially from the lateral semi-circular canal (LSCC) at times from 1 – 4 hours after application. Gentamicin concentration was typically highest in samples originating from the vestibule and was lower in samples originating from scala tympani. To interpret these results, perilymph elimination kinetics for gentamicin was quantified by loading the entire perilymph space by injection at the LSCC with a 500 μg/ml gentamicin solution followed by sequential perilymph sampling from the LSCC after different delay times. This allowed concentration decline in perilymph to be followed with time. Gentamicin was retained well in scala vestibuli and the vestibule but declined rapidly at the base of scala tympani, dominated by interactions of perilymph with CSF, as reported for other substances. Quantitative analysis, taking into account perilymph kinetics for gentamicin, showed that more gentamicin entered at the round window membrane (57%) than at the stapes (35%) but the lower concentrations found in scala tympani were due to greater losses there. The gentamicin levels found in perilymph of the vestibule, which are higher than would be expected from round window entry alone, undoubtedly contribute to the vestibulotoxic effects of the drug. Furthermore, calculations of gentamicin distribution following targeted applications to the RW or stapes are more consistent with cochleotoxicity depending on the gentamicin concentration in scala vestibuli rather than that in scala tympani.

from #Audiology via ola Kala on Inoreader http://ift.tt/2edTKUO
via IFTTT

Top-down and bottom-up neurodynamic evidence in patients with tinnitus

Publication date: Available online 8 October 2016
Source:Hearing Research
Author(s): Sung Kwang Hong, Sejik Park, Min-Hee Ahn, Byoung-Kyong Min
Although a peripheral auditory (bottom-up) deficit is an essential prerequisite for the generation of tinnitus, central cognitive (top-down) impairment has also been shown to be an inherent neuropathological mechanism. Using an auditory oddball paradigm (for top-down analyses) and a passive listening paradigm (for bottom-up analyses) while recording electroencephalograms (EEGs), we investigated whether top-down or bottom-up components were more critical in the neuropathology of tinnitus, independent of peripheral hearing loss. We observed significantly reduced P300 amplitudes (reflecting fundamental cognitive processes such as attention) and evoked theta power (reflecting top-down regulation in memory systems) for target stimuli at the tinnitus frequency of patients with tinnitus but without hearing loss. The contingent negative variation (reflecting top-down expectation of a subsequent event prior to stimulation) and N100 (reflecting auditory bottom-up selective attention) were different between the healthy and patient groups. Interestingly, when tinnitus patients were divided into two subgroups based on their P300 amplitudes, their P170 and N200 components, and annoyance and distress indices to their tinnitus sound were different. EEG theta-band power and its Granger causal neurodynamic results consistently support a double dissociation of these two groups in both top-down and bottom-up tasks. Directed cortical connectivity corroborates that the tinnitus network involves the anterior cingulate and the parahippocampal areas, where higher-order top-down control is generated. Together, our observations provide neurophysiological and neurodynamic evidence revealing a differential engagement of top-down impairment along with deficits in bottom-up processing in patients with tinnitus but without hearing loss.

from #Audiology via ola Kala on Inoreader http://ift.tt/2dJ4sAg
via IFTTT

Quercetin protects against hair cell loss in the zebrafish lateral line and guinea pig cochlea

Publication date: Available online 4 October 2016
Source:Hearing Research
Author(s): Yoshinobu Hirose, Kazuma Sugahara, Eiju Kanagawa, Yousuke Takemoto, Makoto Hashimoto, Hiroshi Yamashita
Eighteen supplement drugs were screened using hair cells to determine a protective effect against the adverse effects of neomycin by using the zebrafish lateral line. The zebrafish were administered the supplement drugs one hour before neomycin exposure. One hour later, animals were fixed in paraformaldehyde. Dose-response curves were generated to evaluate the protective effect on hair cells. The screen identified 3 supplements (quercetin, catechin and tannic acid).Three minutes after exposure to neomycin, increased antioxidant activity was found in the lateral line hair cells, as determined by the analysis of oxidative stress. Quercetin decreases antioxidant activity.The identified drugs were also investigated to determine whether they protect the cochlea against noise-induced hearing loss in guinea pigs. The drugs were administered via the intraperitoneal route in the guinea pigs 3 days before and 4 days after noise exposure. Seven days after noise exposure (130-dB sound pressure level for 3 hours), the auditory brainstem response threshold shifts were assessed. We observed that the auditory brainstem response threshold shift was significantly less in the quercetin group than in the vehicle control group. The results of our study indicate that screening drugs using zebrafish can determine additional protective drugs for the inner ear.

from #Audiology via ola Kala on Inoreader http://ift.tt/2dLiV20
via IFTTT

Effects of sustained release dexamethasone hydrogels in hearing preservation cochlear implantation

Across-site patterns of electrically evoked compound action potential amplitude-growth functions in multichannel cochlear implant recipients and the effects of the interphase gap

Low-frequency bias tone suppression of auditory-nerve responses to low-level clicks and tones

Differences in synaptic and intrinsic properties result in topographic heterogeneity of temporal processing of neurons within the inferior colliculus

Endothelin-1 mediated induction of extracellular matrix genes in strial marginal cells underlies strial pathology in Alport mice

The contribution of inferior colliculus activity to the auditory brainstem response (ABR) in mice

The effects of aging and sex on detection of ultrasonic vocalizations by adult CBA/CaJ mice (Mus musculus)

A fast, stochastic, and adaptive model of auditory nerve responses to cochlear implant stimulation

A tri-coil bellows-type round window transducer with improved frequency characteristics for middle-ear implants

Modelling the effect of round window stiffness on residual hearing after cochlear implantation

Speech perception adjusts to stable spectrotemporal properties of the listening environment

The effect of distraction on change detection in crowded acoustic scenes

Dopaminergic projections of the subparafascicular thalamic nucleus to the auditory brainstem

Graphical abstract

from #Audiology via ola Kala on Inoreader http://ift.tt/2cOhC0O
via IFTTT

Time course and frequency specificity of sub-cortical plasticity in adults following acute unilateral deprivation

Hearing sensitivity differs between zebrafish lines used in auditory research

Study of tonotopic brain changes with functional MRI and FDG-PET in a patient with unilateral objective cochlear tinnitus

Perilymph pharmacokinetics of locally-applied gentamicin in the guinea pig

Top-down and bottom-up neurodynamic evidence in patients with tinnitus

Quercetin protects against hair cell loss in the zebrafish lateral line and guinea pig cochlea

Perilymph pharmacokinetics of locally-applied gentamicin in the guinea pig

Top-down and bottom-up neurodynamic evidence in patients with tinnitus

Perilymph pharmacokinetics of locally-applied gentamicin in the guinea pig

Top-down and bottom-up neurodynamic evidence in patients with tinnitus

Perilymph pharmacokinetics of locally-applied gentamicin in the guinea pig

Publication date: Available online 8 October 2016
Source:Hearing Research
Author(s): A.N. Salt, J.J. Hartsock, R.M. Gill, E. King, F.B. Kraus, S.K. Plontke
Intratympanic gentamicin therapy is widely used clinically to suppress the vestibular symptoms of Meniere’s disease. Dosing in humans was empirically established and we still know remarkably little about where gentamicin enters the inner ear, where it reaches in the inner ear and what time course it follows after local applications. In this study, gentamicin was applied to the round window niche as a 20 μL bolus of 40 mg/ml solution. Ten 2 μL samples of perilymph were collected sequentially from the lateral semi-circular canal (LSCC) at times from 1 – 4 hours after application. Gentamicin concentration was typically highest in samples originating from the vestibule and was lower in samples originating from scala tympani. To interpret these results, perilymph elimination kinetics for gentamicin was quantified by loading the entire perilymph space by injection at the LSCC with a 500 μg/ml gentamicin solution followed by sequential perilymph sampling from the LSCC after different delay times. This allowed concentration decline in perilymph to be followed with time. Gentamicin was retained well in scala vestibuli and the vestibule but declined rapidly at the base of scala tympani, dominated by interactions of perilymph with CSF, as reported for other substances. Quantitative analysis, taking into account perilymph kinetics for gentamicin, showed that more gentamicin entered at the round window membrane (57%) than at the stapes (35%) but the lower concentrations found in scala tympani were due to greater losses there. The gentamicin levels found in perilymph of the vestibule, which are higher than would be expected from round window entry alone, undoubtedly contribute to the vestibulotoxic effects of the drug. Furthermore, calculations of gentamicin distribution following targeted applications to the RW or stapes are more consistent with cochleotoxicity depending on the gentamicin concentration in scala vestibuli rather than that in scala tympani.

from #Audiology via xlomafota13 on Inoreader http://ift.tt/2edTKUO
via IFTTT

Top-down and bottom-up neurodynamic evidence in patients with tinnitus

Publication date: Available online 8 October 2016
Source:Hearing Research
Author(s): Sung Kwang Hong, Sejik Park, Min-Hee Ahn, Byoung-Kyong Min
Although a peripheral auditory (bottom-up) deficit is an essential prerequisite for the generation of tinnitus, central cognitive (top-down) impairment has also been shown to be an inherent neuropathological mechanism. Using an auditory oddball paradigm (for top-down analyses) and a passive listening paradigm (for bottom-up analyses) while recording electroencephalograms (EEGs), we investigated whether top-down or bottom-up components were more critical in the neuropathology of tinnitus, independent of peripheral hearing loss. We observed significantly reduced P300 amplitudes (reflecting fundamental cognitive processes such as attention) and evoked theta power (reflecting top-down regulation in memory systems) for target stimuli at the tinnitus frequency of patients with tinnitus but without hearing loss. The contingent negative variation (reflecting top-down expectation of a subsequent event prior to stimulation) and N100 (reflecting auditory bottom-up selective attention) were different between the healthy and patient groups. Interestingly, when tinnitus patients were divided into two subgroups based on their P300 amplitudes, their P170 and N200 components, and annoyance and distress indices to their tinnitus sound were different. EEG theta-band power and its Granger causal neurodynamic results consistently support a double dissociation of these two groups in both top-down and bottom-up tasks. Directed cortical connectivity corroborates that the tinnitus network involves the anterior cingulate and the parahippocampal areas, where higher-order top-down control is generated. Together, our observations provide neurophysiological and neurodynamic evidence revealing a differential engagement of top-down impairment along with deficits in bottom-up processing in patients with tinnitus but without hearing loss.

from #Audiology via xlomafota13 on Inoreader http://ift.tt/2dJ4sAg
via IFTTT

HDR syndrome in a Japanese girl with biliary atresia: a case report.

HDR syndrome in a Japanese girl with biliary atresia: a case report.

BMC Pediatr. 2016 Jan 22;16:14

Authors: Higuchi Y, Hasegawa K, Yamashita M, Fujii Y, Tanaka H, Tsukahara H

Abstract
BACKGROUND: Hypoparathyroidism, sensorineural deafness, and renal dysplasia (HDR) syndrome is an autosomal dominant disorder. We report the first detailed case of hypoparathyroidism complicated by biliary atresia.
CASE PRESENTATION: A 1-year-old Japanese girl was admitted to our hospital for living donor liver transplantation. She suffered from obstructive jaundice owing to biliary atresia. She also had persistent hypocalcemia. Despite oral calcium and abundant vitamin D supplementation, a laboratory test showed hypocalcemia (1.4 mmol/l) and hyperphosphatemia (2.6 mmol/l). The intact parathyroid hormone level was normal (66 ng/l) with severe vitamin D deficiency (25-hydroxy vitamin D: undetectable levels). There were no rachitic changes in metaphysis on X-rays. Her family history showed that her mother had sensorineural deafness, a low serum calcium level (2.1 mmol/l), hypoplastic left kidney, and a past history of an operation for right vesicoureteral reflux. We suspected that this patient and her mother have hypoparathyroidism, sensorineural deafness, and renal dysplasia syndrome. A heterozygous GATA3 gene mutation (c.736delGinsAT) was found in this patient and her mother, but not in her father.
CONCLUSION: This familial case confirms the importance of family history in the diagnosis of HDR syndrome. Regardless of marked vitamin D deficiency, the complication of hypoparathyroidism prevented the onset of vitamin D deficiency rickets in our patient.

PMID: 26800885 [PubMed - indexed for MEDLINE]

from #Audiology via xlomafota13 on Inoreader http://ift.tt/2dUIpu3
via IFTTT

c.376G>A mutation in WFS1 gene causes Wolfram syndrome without deafness.

http:--linkinghub.elsevier.com-ihub-imag

c.376G>A mutation in WFS1 gene causes Wolfram syndrome without deafness.

Eur J Med Genet. 2016 Feb;59(2):65-9

Authors: Safarpour Lima B, Ghaedi H, Daftarian N, Ahmadieh H, Jamshidi J, Khorrami M, Noroozi R, Sohrabifar N, Assarzadegan F, Hesami O, Taghavi S, Ahmadifard A, Atakhorrami M, Rahimi-Aliabadi S, Shahmohammadibeni N, Alehabib E, Andarva M, Darvish H, Emamalizadeh B

Abstract
Wolfram syndrome is one of the rare autosomal recessive, progressive, neurodegenerative disorders, characterized by diabetes mellitus and optic atrophy. Several other features are observed in patients including deafness, ataxia, and peripheral neuropathy. A gene called WFS1 is identified on chromosome 4p, responsible for Wolfram syndrome. We investigated a family consisted of parents and 8 children, which 5 of them have been diagnosed for Wolfram syndrome. WFS1 gene in all family members was sequenced for causative mutations. A mutation (c.376G>A, p.A126T) was found in all affected members in homozygous state and in both parents in heterozygous state. The bioinformatics analysis showed the deleterious effects of this nucleotide change on the structure and function of the protein product. As all of the patients in the family showed the homozygote mutation, and parents were both heterozygote, this mutation is probably the cause of the disease. We identified this mutation in homozygous state for the first time as Wolfram syndrome causation. We also showed that this mutation probably doesn't cause deafness in affected individuals.

PMID: 26773575 [PubMed - indexed for MEDLINE]

from #Audiology via xlomafota13 on Inoreader http://ift.tt/2dUIVIs
via IFTTT

Comparison of threshold estimation in infants with hearing loss or normal hearing using auditory steady-state response evoked by narrow band CE-chirps and auditory brainstem response evoked by tone pips.

Comparison of threshold estimation in infants with hearing loss or normal hearing using auditory steady-state response evoked by narrow band CE-chirps and auditory brainstem response evoked by tone pips.

Int J Audiol. 2016 Oct 7;:1-7

Authors: Michel F, Jørgensen KF

Abstract
OBJECTIVE: The objective of this study is to compare air-conduction thresholds obtained with ASSR evoked by narrow band (NB) CE-chirps and ABR evoked by tone pips (tpABR) in infants with various degrees of hearing loss.
DESIGN: Thresholds were measured at 500, 1000, 2000 and 4000 Hz. Data on each participant were collected at the same day.
STUDY SAMPLE: Sixty-seven infants aged 4 d to 22 months (median age = 96 days), resulting in 57, 52, 87 and 56 ears for 500, 1000, 2000 and 4000 Hz, respectively.
RESULTS: Statistical analysis was performed for ears with hearing loss (HL) and showed a very strong correlation between tpABR and ASSR evoked by NB CE-chirps: 0.90 (n = 28), 0.90 (n = 28), 0.96 (n = 42) and 0.95 (n = 30) for 500, 1000, 2000 and 4000 Hz, respectively. At these frequencies, the mean difference between tpABR and ASSR was -3.6 dB (± 7.0), -5.2 dB (± 7.3), -3.9 dB (± 5.2) and -5.2 dB (± 4.7). Linear regression analysis indicated that the relationship was not influenced by the degree of hearing loss.
CONCLUSION: We propose that dB nHL to dB eHL correction values for ASSR evoked by NB CE-chirps should be 5 dB lower than values used for tpABR.

PMID: 27715342 [PubMed - as supplied by publisher]

from #Audiology via ola Kala on Inoreader http://ift.tt/2dUEn4N
via IFTTT

Epidemiology and risk factors for tinnitus after leisure noise exposure in Flemish young adults.

Epidemiology and risk factors for tinnitus after leisure noise exposure in Flemish young adults.

Int J Audiol. 2016 Oct 7;:1-9

Authors: Degeest S, Keppler H, Corthals P, Clays E

Abstract
OBJECTIVE: Young people regularly expose themselves to leisure noise and are at risk of acquiring tinnitus. This study examined the prevalence of leisure noise-induced tinnitus among Flemish young adults as well as the relation with sociodemographic factors, health-related variables and attitudes and beliefs towards noise.
DESIGN: A self-administered questionnaire was used to evaluate the presence of noise-induced tinnitus, the amount of leisure noise and attitudes towards noise and hearing protection.
STUDY SAMPLE: 517 subjects between 18 and 30 years were included.
RESULTS: Temporary and chronic tinnitus occurred in 68.5% and 6.4% of the sample, respectively. Chronic tinnitus was more prevalent in male subjects and associated with more hearing-related symptoms. Furthermore, subjects with chronic tinnitus were more aware of the risks of noise and the importance of hearing protection. Finally, higher levels of leisure noise were independently associated with chronic tinnitus.
CONCLUSIONS: Tinnitus is observed frequently in young adults. Results also indicate that persons with chronic tinnitus were exposed to a higher noise dose during their lives. Longitudinal studies may be useful to evaluate whether the experience of chronic tinnitus has led to behavioural changes. These findings further underpin the importance of educating youth about the risks of leisure noise exposure.

PMID: 27715331 [PubMed - as supplied by publisher]

from #Audiology via ola Kala on Inoreader http://ift.tt/2dUFgdH
via IFTTT

Comparison of threshold estimation in infants with hearing loss or normal hearing using auditory steady-state response evoked by narrow band CE-chirps and auditory brainstem response evoked by tone pips.

Int J Audiol. 2016 Oct 7;:1-7

Authors: Michel F, Jørgensen KF

PMID: 27715342 [PubMed - as supplied by publisher]

from #Audiology via ola Kala on Inoreader http://ift.tt/2dUEn4N
via IFTTT

Epidemiology and risk factors for tinnitus after leisure noise exposure in Flemish young adults.

Epidemiology and risk factors for tinnitus after leisure noise exposure in Flemish young adults.

Int J Audiol. 2016 Oct 7;:1-9

Authors: Degeest S, Keppler H, Corthals P, Clays E

PMID: 27715331 [PubMed - as supplied by publisher]

from #Audiology via ola Kala on Inoreader http://ift.tt/2dUFgdH
via IFTTT

Πληροφορίες

Σάββατο 8 Οκτωβρίου 2016

Graphical abstract

Graphical abstract