Best frequencies and temporal delays are similar across the low-frequency regions of the guinea pig cochlea

Burwood, George W. S.; Hakizimana, Pierre; Nuttall, Alfred L.; Fridberger, Anders

doi:10.1126/sciadv.abq2773

Cited by 13 publications

(8 citation statements)

References 41 publications

(47 reference statements)

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“…Moreover, confocal imaging of the hearing organ in vivo showed that the native hair cell morphology is well preserved in the temporal bone preparation [ 33 ] and its sound-evoked electrical responses (see below) are generally consistent with those recorded in vivo in terms of amplitude and nonlinear dependency in sound intensity [ 34 ]. In addition, we recently used a modified version of this preparation (albeit with a larger apical cochlear opening than usual) to investigate low frequency encoding by the hearing organ and the results were consistent with those we obtained in unopened cochlea in vivo [ 35 ].…”

Section: Resultssupporting

confidence: 69%

The summating potential polarity encodes the ear health condition

Hakizimana

2023

Cell. Mol. Life Sci.

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The summating potential (SP), the DC potential which, along with the AC response, is produced when the hair cells convert the vibrational mechanical energy of sound into electrical signals, is the most enigmatic of the cochlear potentials because its polarity and function have remained elusive for more than seven decades. Despite the tremendous socioeconomic consequences of noise-induced hearing loss and the profound physiological importance of understanding how loud noise exposure impairs the hair cell receptor activation, the relationship between the SP and noise-induced hearing impairment remains poorly characterized. Here, I show that in normally hearing ears, the SP polarity is positive and its amplitude relative to the AC response grows exponentially across frequencies, and becomes negative and decreases exponentially across frequencies following noise-induced hearing injury. Since the SP is thought to be generated by K+ outflow down the gradient through the hair cell basolateral K+ channels, the SP polarity switch to negative values is consistent with a noise-induced shift in the operating point of the hair cells.

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Section: Resultssupporting

confidence: 69%

The summating potential polarity encodes the ear health condition

Hakizimana

2023

Cell. Mol. Life Sci.

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“…The guinea pig temporal bone preparation is a widely used cochlear model for investigating sound transduction mechanisms [ 5 , 14 – 16 , 18 , 21 – 24 , 45 , 47 , 49 ]. Recently, I employed a meticulous approach using the experimental preparation above to compile a rich dataset of sound transduction AC responses [ 21 ].…”

Section: Resultsmentioning

confidence: 99%

The sensitivity of mechanoelectrical transduction response phase to acoustic overstimulation is calcium-dependent

Hakizimana

2023

Pflugers Arch - Eur J Physiol

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The Mechanoelectrical transduction (MET) channels of the mammalian hair cells are essential for converting sound stimuli into electrical signals that enable hearing. However, the impact of acoustic overstimulation, a leading cause of hearing loss, on the MET channel function remains poorly understood. In this study, I investigated the effect of loud sound-induced temporary threshold shift (TTS) on the transduction response phase across a wide range of sound frequencies and amplitudes. The results demonstrated an increase in the transduction response phase following TTS, indicating altered transduction apparatus function. Further investigations involving the reduction of extracellular calcium, a known consequence of TTS, replicated the observed phase changes. Additionally, reduction of potassium entry confirmed the specific role of calcium in regulating the transduction response phase. These findings provide novel insights into the impact of loud sound exposure on hearing impairment at the transduction apparatus level and highlight the critical role of calcium in modulating sound transduction. Considering that over 1 billion teenagers and young adults globally are at risk of hearing loss due to unsafe music listening habits, these results could significantly enhance awareness about the damaging effects of loud sound exposure.

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“…A gradient in EP, decreasing from cochlear base to apex, has been observed in several species ( 65 , 67 , 69 , 70 ). Whether this relates to the physiological grounds of hair cell tuning and low-frequency coding is unknown ( 71 , 72 ). Collectively, this could indicate that the EP generation is more prominent in the base that spreads apically, conceivably to fulfill high-frequency dependent outer hair cell electro-motility and place-coding.…”

Section: Discussionmentioning

confidence: 99%

Immuno-surveillance and protection of the human cochlea

Liu,

Li,

Kämpfe Nordström

et al. 2024

Front. Neurol.

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BackgroundDespite its location near infection-prone areas, the human inner ear demonstrates remarkable resilience. This suggests that there are inherent instruments deterring the invasion and spread of pathogens into the inner ear. Here, we combined high-resolution light microscopy, super-resolution immunohistochemistry (SR-SIM) and synchrotron phase contrast imaging (SR-PCI) to identify the protection and barrier systems in the various parts of the human inner ear, focusing on the lateral wall, spiral ganglion, and endolymphatic sac.Materials and methodsLight microscopy was conducted on mid-modiolar, semi-thin sections, after direct glutaraldehyde/osmium tetroxide fixation. The tonotopic locations were estimated using SR-PCI and 3D reconstruction in cadaveric specimens. The sections were analyzed for leucocyte and macrophage activity, and the results were correlated with immunohistochemistry using confocal microscopy and SR-SIM.ResultsLight microscopy revealed unprecedented preservation of cell anatomy and several macrophage-like cells that were localized in the cochlea. Immunohistochemistry demonstrated IBA1 cells frequently co-expressing MHC II in the spiral ganglion, nerve fibers, lateral wall, spiral limbus, and tympanic covering layer at all cochlear turns as well as in the endolymphatic sac. RNAscope assays revealed extensive expression of fractalkine gene transcripts in type I spiral ganglion cells. CD4 and CD8 cells occasionally surrounded blood vessels in the modiolus and lateral wall. TMEM119 and P2Y12 were not expressed, indicating that the cells labeled with IBA1 were not microglia. The round window niche, compact basilar membrane, and secondary spiral lamina may form protective shields in the cochlear base.DiscussionThe results suggest that the human cochlea is surveilled by dwelling and circulating immune cells. Resident and blood-borne macrophages may initiate protective immune responses via chemokine signaling in the lateral wall, spiral lamina, and spiral ganglion at different frequency locations. Synchrotron imaging revealed intriguing protective barriers in the base of the cochlea. The role of the endolymphatic sac in human inner ear innate and adaptive immunity is discussed.

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Best frequencies and temporal delays are similar across the low-frequency regions of the guinea pig cochlea

Cited by 13 publications

References 41 publications

The summating potential polarity encodes the ear health condition

The summating potential polarity encodes the ear health condition

The sensitivity of mechanoelectrical transduction response phase to acoustic overstimulation is calcium-dependent

Immuno-surveillance and protection of the human cochlea

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