Biology subjects

Dewey, J. B.

Publications and source records attributed to Dewey, J. B..

4 recordsLinked to original sources

bioRxiv2026

Broadband amplification of organ of Corti vibrations in the mouse cochlear apex

Mammalian hearing depends on the active amplification of sound-evoked waves as they travel along the basilar membrane within the cochlea. This amplification is mediated by the outer hair cells (OHCs), which generate force to enhance the vibrations of the surrounding structures. While OHCs at a given location only amplify basilar membrane motion for a narrow frequency range, recent measurements show that the amplification of motions deeper within the organ of Corti is much more broadband. However, the extent to which this broadband amplification influences the motions that are most relevant to inner hair cell stimulation - i.e., at the organs apical surface - remains uncertain. Here, optical coherence tomography was used to demonstrate that OHCs nonlinearly amplify the motions near the top of the organ of Corti, including at the reticular lamina and tectorial membrane, over a wide frequency range in the mouse cochlear apex. Responses at all frequencies were physiologically vulnerable and grew compressively with stimulus level. Low-frequency responses also exhibited non-monotonic features that were due to interference between amplified motion and the underlying traveling wave. The data suggest that broadband amplification of motions at the top of the organ of Corti likely explains certain phenomena observed in auditory nerve responses.

neuroscience↗

bioRxiv2024

Tonic sound-evoked motility of cochlear outer hair cells in mice with impaired mechanotransduction

Cochlear outer hair cells (OHCs) transduce sound-induced vibrations of their stereociliary bundles into receptor potentials that drive changes in cell length. While fast, phasic OHC length changes are thought to underlie an amplification process required for sensitive hearing, OHCs also exhibit large tonic length changes. The origins and functional significance of this tonic motility are unclear. Here, in vivo cochlear vibration measurements reveal tonic, sound-induced OHC motility in mice with stereociliary defects that impair mechanotransduction and eliminate cochlear amplification. Tonic motility in impaired mice was physiologically vulnerable but weakly related to any residual phasic motility, possibly suggesting a dissociation between the underlying mechanisms. Nevertheless, a simple model demonstrates how tonic responses in both normal and impaired mice can result from asymmetric mechanotransduction currents and be large even when phasic motility is undetectable. Tonic OHC responses are therefore not unique to sensitive ears, though their potential functional role remains uncertain.

neuroscience↗

bioRxiv2021

Reconstruction of sound driven, actively amplified and spontaneous motions within the tree cricket auditory organ

AO_SCPLOWBSTRACTC_SCPLOWHearing consists of a delicate chain of events. Sound is first captured by an eardrum or similar organ which is set into vibrations, these vibrations must then be transmitted to sensory cells in a manner that opens mechanosensory channels generating an electrical signal. Studying this process is challenging. Auditory vibrations are in the nano- to picometer-scale and occur at fast temporal scales of milli to microseconds. Finally, most of this process occurs within the body of the animal where it is inaccessible to conventional measurement techniques. For instance, even in crickets, a century-old auditory model system, it is unclear how sound evoked vibrations are transmitted to sensory neurons. Here, we use optical coherence tomography (OCT) to measure how vibrations travel within the auditory organ of the western tree cricket (Oecanthus californicus). We also measure the reversal of this process as mechanosensory cells generate spontaneous oscillations and amplify sound-evoked vibrations. Most importantly, we found that while the mechanosensory neurons were not attached to the peripheral sound collecting structures, they were mechanically well-coupled through acoustic trachea. Thus, the acoustic trachea are not merely conduits for sound but also perform a mechanical function. Our results generate several insights into the similarities between insect and vertebrate hearing, and into the evolutionary history of auditory amplification.

biophysics↗

bioRxiv2018

LMO7 deficiency reveals the significance of the cuticular plate for hearing function

Sensory hair cells, the mechanoreceptors of the auditory and vestibular system, harbor two specialized organelles, the hair bundle and the cuticular plate. Both subcellular structures have adapted to facilitate the remarkable sensitivity and speed of hair cell mechanotransduction. While the mechanosensory hair bundle is extensively studied, the molecules and mechanisms mediating the development and function of the cuticular plate are poorly understood. The cuticular plate is believed to provide a rigid foundation for stereociliar pivot movements, but specifics about its function, especially the significance of its integrity for long-term maintenance of hair cell mechanotransduction, are not known. In this study, we describe the discovery of a hair cell protein called LIM only protein 7 (LMO7). In the hair cell, LMO7 is specifically localized in the cuticular plate. Lmo7 KO mice suffer multiple deficiencies in the cuticular plate, including reduced filamentous actin density and abnormal length and distribution of stereociliar rootlets. In addition to the cuticular plate defects, older Lmo7 KO mice develop abnormalities in inner hair cell stereocilia. Together, these defects affect cochlear tuning and sensitivity and give rise to late-onset progressive hearing loss.

neuroscience↗