| 1. |
- Burwood, George, et al.
(författare)
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Best frequencies and temporal delays are similar across the low-frequency regions of the guinea pig cochlea
- 2022
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Ingår i: Science Advances. - : AMER ASSOC ADVANCEMENT SCIENCE. - 2375-2548. ; 8:38
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Tidskriftsartikel (refereegranskat)abstract
- The cochlea maps tones with different frequencies to distinct anatomical locations. For instance, a faint 5000-hertz tone produces brisk responses at a place approximately 8 millimeters into the 18-millimeter-long guinea pig cochlea, but little response elsewhere. This place code pervades the auditory pathways, where neurons have "best frequencies" determined by their connections to the sensory cells in the hearing organ. However, frequency selectivity in cochlear regions encoding low-frequency sounds has not been systematically studied. Here, we show that low-frequency hearing works according to a unique principle that does not involve a place code. Instead, sound-evoked responses and temporal delays are similar across the low-frequency regions of the cochlea. These findings are a break from theories considered proven for 100 years and have broad implications for understanding information processing in the brainstem and cortex and for optimizing the stimulus delivery in auditory implants.
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| 2. |
- Burwood, G., et al.
(författare)
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Outer hair cell driven reticular lamina mechanical distortion in living cochleae
- 2022
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Ingår i: Hearing Research. - : ELSEVIER. - 0378-5955 .- 1878-5891. ; 423
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Tidskriftsartikel (refereegranskat)abstract
- Cochlear distortions afford researchers and clinicians a glimpse into the conditions and properties of inner ear signal processing mechanisms. Until recently, our examination of these distortions has been limited to measuring the vibration of the basilar membrane or recording acoustic distortion output in the ear canal. Despite its importance, the generation mechanism of cochlear distortion remains a substantial task to understand. The ability to measure the vibration of the reticular lamina in rodent models is a recent experimental advance. Surprising mechanical properties have been revealed. These properties merit both discussion in context with our current understanding of distortion, and appraisal of the significance of new interpretations of cochlear mechanics. This review focusses on some of the recent data from our research groups and discusses the implications of these data on our understanding of vocalization processing in the periphery, and their influence upon future experimental directions. (C) 2021 Elsevier B.V. All rights reserved.
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| 3. |
- Hakizimana, Pierre, 1976-, et al.
(författare)
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Inner hair cell stereocilia are embedded in the tectorial membrane
- 2021
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Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Mammalian hearing depends on sound-evoked displacements of the stereocilia of inner hair cells (IHCs), which cause the endogenous mechanoelectrical transducer channels to conduct inward currents of cations including Ca2+. Due to their presumed lack of contacts with the overlaying tectorial membrane (TM), the putative stimulation mechanism for these stereocilia is by means of the viscous drag of the surrounding endolymph. However, despite numerous efforts to characterize the TM by electron microscopy and other techniques, the exact IHC stereocilia-TM relationship remains elusive. Here we show that Ca2+-rich filamentous structures, that we call Ca2+ ducts, connect the TM to the IHC stereocilia to enable mechanical stimulation by the TM while also ensuring the stereocilia access to TM Ca2+. Our results call for a reassessment of the stimulation mechanism for the IHC stereocilia and the TM role in hearing.
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| 4. |
- He, Wenxuan, et al.
(författare)
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An outer hair cell-powered global hydromechanical mechanism for cochlear amplification
- 2022
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Ingår i: Hearing Research. - : ELSEVIER. - 0378-5955 .- 1878-5891. ; 423
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Forskningsöversikt (refereegranskat)abstract
- It is a common belief that the mammalian cochlea achieves its exquisite sensitivity, frequency selectiv-ity, and dynamic range through an outer hair cell-based active process, or cochlear amplification. As a sound-induced traveling wave propagates from the cochlear base toward the apex, outer hair cells at a narrow region amplify the low level sound-induced vibration through a local feedback mechanism. This widely accepted theory has been tested by measuring sound-induced sub-nanometer vibrations within the organ of Corti in the sensitive living cochleae using heterodyne low-coherence interferometry and optical coherence tomography. The aim of this short review is to summarize experimental findings on the cochlear active process by the authors group. Our data show that outer hair cells are able to gener-ate substantial forces for driving the cochlear partition at all audible frequencies in vivo. The acoustically induced reticular lamina vibration is larger and more broadly tuned than the basilar membrane vibration. The reticular lamina and basilar membrane vibrate approximately in opposite directions at low frequen-cies and in the same direction at the best frequency. The group delay of the reticular lamina is larger than that of the basilar membrane. The magnitude and phase differences between the reticular lamina and basilar membrane vibration are physiologically vulnerable. These results contradict predictions based on the local feedback mechanism but suggest a global hydromechanical mechanism for cochlear amplifi-cation. This article is part of the Special Issue Outer hair cell Edited by Joseph Santos-Sacchi and Kumar Navaratnam. (c) 2021 Elsevier B.V. All rights reserved.
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| 5. |
- He, Wenxuan, et al.
(författare)
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The reticular lamina and basilar membrane vibrations in the transverse direction in the basal turn of the living gerbil cochlea
- 2022
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Ingår i: Scientific Reports. - : NATURE PORTFOLIO. - 2045-2322. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- The prevailing theory of cochlear function states that outer hair cells amplify sound-induced vibration to improve hearing sensitivity and frequency specificity. Recent micromechanical measurements in the basal turn of gerbil cochleae through the round window have demonstrated that the reticular lamina vibration lags the basilar membrane vibration, and it is physiologically vulnerable not only at the best frequency but also at the low frequencies. These results suggest that outer hair cells from a broad cochlear region enhance hearing sensitivity through a global hydromechanical mechanism. However, the time difference between the reticular lamina and basilar membrane vibration has been thought to result from a systematic measurement error caused by the optical axis non-perpendicular to the cochlear partition. To address this concern, we measured the reticular lamina and basilar membrane vibrations in the transverse direction through an opening in the cochlear lateral wall in this study. Present results show that the phase difference between the reticular lamina and basilar membrane vibration decreases with frequency by similar to 180 degrees from low frequencies to the best frequency, consistent with those measured through the round window. Together with the round-window measurement, the low-coherence interferometry through the cochlear lateral wall demonstrates that the time difference between the reticular lamina and basilar membrane vibration results from the cochlear active processing rather than a measurement error.
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| 6. |
- Prasad, Sonal, 1988-, et al.
(författare)
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Radixin modulates the function of outer hair cell stereocilia
- 2020
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Ingår i: Communications Biology. - : Nature Research. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- The stereocilia of the inner ear sensory cells contain the actin-binding protein radixin, encoded by RDX. Radixin is important for hearing but remains functionally obscure. To determine how radixin influences hearing sensitivity, we used a custom rapid imaging technique to visualize stereocilia motion while measuring electrical potential amplitudes during acoustic stimulation. Radixin inhibition decreased sound-evoked electrical potentials. Other functional measures, including electrically induced sensory cell motility and sound-evoked stereocilia deflections, showed a minor amplitude increase. These unique functional alterations demonstrate radixin as necessary for conversion of sound into electrical signals at acoustic rates. We identified patients with RDX variants with normal hearing at birth who showed rapidly deteriorating hearing during the first months of life. This may be overlooked by newborn hearing screening and explained by multiple disturbances in postnatal sensory cells. We conclude radixin is necessary for ensuring normal conversion of sound to electrical signals in the inner ear.
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| 7. |
- Vural, Mert, et al.
(författare)
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Soft Electromagnetic Vibrotactile Actuators with Integrated Vibration Amplitude Sensing
- 2023
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Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 15:25, s. 30653-30662
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Tidskriftsartikel (refereegranskat)abstract
- Soft vibrotactile devices have the potential to expandthe functionalityof emerging electronic skin technologies. However, those devices oftenlack the necessary overall performance, sensing-actuation feedbackand control, and mechanical compliance for seamless integration onthe skin. Here, we present soft haptic electromagnetic actuators thatconsist of intrinsically stretchable conductors, pressure-sensitiveconductive foams, and soft magnetic composites. To minimize jouleheating, high-performance stretchable composite conductors are developedbased on in situ-grown silver nanoparticles formed within the silverflake framework. The conductors are laser-patterned to form soft anddensely packed coils to further minimize heating. Soft pressure-sensitiveconducting polymer-cellulose foams are developed and integrated totune the resonance frequency and to provide internal resonator amplitudesensing in the resonators. The above components together with a softmagnet are assembled into soft vibrotactile devices providing high-performanceactuation combined with amplitude sensing. We believe that soft hapticdevices will be an essential component in future developments of multifunctionalelectronic skin for future human-computer and human-roboticinterfaces.
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| 8. |
- Wang, Bei, et al.
(författare)
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Liquid Metal-Based High-Density Interconnect Technology for Stretchable Printed Circuits
- 2023
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Ingår i: Advanced Functional Materials. - : WILEY-V C H VERLAG GMBH. - 1616-301X .- 1616-3028.
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Tidskriftsartikel (refereegranskat)abstract
- High-density interconnect (HDI) technology for liquid metal (LM)-based stretchable printed circuit boards is crucial for expanding their applicability. HDI technology provides high-resolution multilayer circuits with a high density of components, as required for next generation of neuroprobes and ultrasonic and sensor arrays. This study presents a HDI technique utilizing laser engraved micro grooves in silicone with a protective lift-off mask of polyvinyl alcohol (PVA) and subsequent microscale LM particle spray deposition. This approach achieves high-resolution LM patterns and enables multilayer connectivity and high-density integration of components simultaneously, that is, realizing HDI technology. It is demonstrated using a stretchable 0201 LED display with a density of six leads per mm2 and a cochlear implant (CI) electrode array. The demonstrated manufacturing of the CI has the potential to enable fully automated printed circuit board manufacturing of such implants with increased precision and throughput. Implants in guinea pigs show that the CI is capable of activating the auditory neuron with electrical auditory brainstem response (eABR) and electrical compound action potential (eCAP) of high quality. Moreover, the U-shaped cross section of the LM interconnects provides a higher mechanical shock resistance of the circuit than that of normal rectangular cross sections. A liquid metal based high-density interconnect technology that is capable of fabricating high resolution circuits and integrating electronic high-density components in multilayer stretchable system, which are demonstrated by a stretchable high-density integrated LEDs display and an eight-electroe array of a cochlear implant.image
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| 9. |
- Wang, Bei, et al.
(författare)
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Softer, thinner and more complaint cochlear implants with liquid metal
- 2022
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Konferensbidrag (refereegranskat)abstract
- A cochlear implant (CI) can restore sound perception for people with congenital or sensorineural hearing loss. Liquid metal (LM) based CI is more soft and complaint, enhancing its compliance and reducing intra-cochlear trauma, but the LM pattern demands high resolution. This work introduces a PCB manufacturing technique for high-resolution LM-based cochlear implant fabrication. It consists of laser cutting and ablation, masked LM microscale spray deposition, lift-off, and encapsulation. The microscale deposition is capable of patterning uniform LM at high resolution by fine spraying a sonication-produced LM particle based ink. A novel feature is that the laser-processable substrate is engraved when cutting the protective lift-off mask, avoiding mask transfer by lamination and allowing for alignment, vias, and higher aspect ratio structures, at high resolution. This feature simplifies the whole process and improves the precision and yield, allowing for more complex circuits. The fabricated CI shows good performance both in the inserting process and electrical signal.
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| 10. |
- Zhang, Jinhui, et al.
(författare)
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VEGFA165 gene therapy ameliorates blood-labyrinth barrier breakdown and hearing loss
- 2021
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Ingår i: JCI Insight. - : American Society for Clinical Investigation. - 2379-3708. ; 6:8
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Tidskriftsartikel (refereegranskat)abstract
- Millions of people are affected by hearing loss. Hearing loss is frequently caused by noise or aging and often associated with loss of pericytes. Pericytes populate the small vessels in the adult cochlea. However, their role in different types of hearing loss is largely unknown. Using an inducible and conditional pericyte depletion mouse model and noise-exposed mouse model, we show that loss of pericytes leads to marked changes in vascular structure, in turn leading to vascular degeneration and hearing loss. In vitro, using advanced tissue explants from pericyte fluorescence reporter models combined with exogenous donor pericytes, we show that pericytes, signaled by VEGF isoform A165 (VEGFA165), vigorously drive new vessel growth in both adult and neonatal mouse inner ear tissue. In vivo, the delivery of an adeno-associated virus serotype 1-mediated (AAV1-mediated) VEGFA165 viral vector to pericyte-depleted or noise-exposed animals prevented and regenerated lost pericytes, improved blood supply, and attenuated hearing loss. These studies provide the first clear-cut evidence that pericytes are critical for vascular regeneration, vascular stability, and hearing in adults. The restoration of vascular function in the damaged cochlea, including in noise-exposed animals, suggests that VEGFA165 gene therapy could be a new strategy for ameliorating vascular associated hearing disorders.
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| 11. |
- Zhao, Mingduo, et al.
(författare)
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Vibration direction sensitivity of the cochlea with bone conduction stimulation in guinea pigs
- 2021
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Ingår i: Scientific Reports. - : Nature Research. - 2045-2322. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Sound and vibrations that cause the skull bone to vibrate can be heard as ordinary sounds and this is termed hearing by bone conduction (BC). Not all mechanisms that causes a skull vibration to result in BC hearing are known, and one such unknown is how the direction of the vibration influences BC hearing. This direction sensitivity was investigated by providing BC stimulation in five different directions at the vertex of the guinea pig skull. The hearing thresholds for BC stimulation was obtained in the frequency range of 2 to 20 kHz by measurements of compound action potential. During the stimulation by BC, the vibration of the cochlear promontory was measured with a three-dimensional laser Doppler vibrometer resulting in a set of unique three-dimensional velocity magnitude combinations for each threshold estimation. The sets of three-dimensional velocity magnitude at threshold were used to investigate nine different predictors of BC hearing based on cochlear promontory velocity magnitudes, six single direction (x, y and z directions in isolation, the normal to the stapes footplate, the oval to round window direction, and the cochlear base to apex direction), one linear combination of the three dimension velocity magnitudes, one square-rooted sum of the squared velocity magnitudes, and one sum of the weighted three dimensional velocity magnitudes based on a restricted minimum square error (MSE) estimation. The MSE gave the best predictions of the hearing threshold based on the cochlear promontory velocity magnitudes while using only a single direction gave the worst predictions of the hearing thresholds overall. According to the MSE estimation, at frequencies up to 8 kHz the vibration direction between the right and left side gave the greatest contribution to BC hearing in the guinea pig while at the highest frequencies measured, 16 and 20 kHz, the anteroposterior direction of the guinea pig head gave the greatest contribution.
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