Auditory Research publications

Methicillin-resistant Staphylococcus aureus (MRSA) is a significant pathogen in otitis media (OM), including acute otitis media (AOM) and chronic suppurative otitis media (CSOM), presenting considerable therapeutic challenges due to its biofilm formation, host immune evasion, and promotion of persistent inflammation. This study evaluated the therapeutic potential of Schisandrin C (Sch C), a natural lignan derived from Schisandra chinensis , in mitigating MRSA-induced OM. In rat models of MRSA-induced AOM and CSOM, Sch C significantly reduced bacterial load and inflammatory responses by decreasing pro-inflammatory cytokine levels. By upregulating tight junction protein ZO-1 and downregulating mucin MUC5B, it also restored epithelial barrier integrity. In addition, Sch C treatment improved auditory function. Mechanistic studies revealed that Sch C directly inhibited sortase A (SrtA), a key enzyme responsible for anchoring surface virulence factors in MRSA, by binding to its active site and inhibiting its transpeptidase activity (fluorescence resonance energy transfer IC₅₀ = 38.68 µM). Through inhibiting SrtA, Sch C disrupted MRSA adhesion, invasion, and biofilm formation without exerting direct bactericidal effects. Furthermore, Sch C synergized with ofloxacin, enhancing its efficacy against MRSA otitis by reducing bacterial load, inflammation, and tissue damage. Collectively, these findings establish Sch C as a potent S. aureus SrtA inhibitor, highlighting its promise as a therapeutic strategy for MRSA-induced OM.

Neonatal bilirubin encephalopathy is primarily characterized by central auditory dysfunction and cognitive impairments. However, the precise molecular mechanisms underlying bilirubin-induced neurotoxicity remain poorly understood, hindering the development of effective therapeutic strategies. Using kinase activity prediction tools based on quantitative phosphoproteomics, we identified ROCK2 (Rho-associated protein kinase 2) as a critical kinase regulating the phosphorylation of proteins associated with bilirubin exposure. Molecular docking and MicroScale Thermophoresis assays revealed a strong binding affinity between bilirubin and ROCK2. Interestingly, bilirubin increased ROCK2 protein expression without affecting its mRNA levels, and cycloheximide chase assays revealed enhanced ROCK2 stability, implicating post-translational regulation. While bilirubin did not directly activate ROCK2 kinase activity in vitro, it elevated phosphorylation of its substrate LIMK1, suggesting that ROCK2 accumulation amplifies downstream signaling. In primary rat neurons, ROCK2 inhibitors (Belumosudil and Y-27632) ameliorated bilirubin-induced loss of mitochondrial membrane potential and neuronal cell death. Furthermore, using ROCK2 inhibitors and Rock2+/- mice, we demonstrated that modulation of ROCK2 significantly alleviated bilirubin-induced auditory deficits and cognitive impairments. These behavioral improvements were linked to restored excitatory synaptic transmission in the cochlear nucleus and reduced dendritic damage in hippocampal neurons. These findings position ROCK2 as a promising molecular target for therapeutic intervention in bilirubin encephalopathy.

Background Noise-induced hearing loss (NIHL) is the second leading cause of deafness globally. However, effective pharmacological treatments remain unavailable. Excitotoxicity, an early NIHL event, is a central mechanism in degeneration of cochlear synapses established between inner hair cells (IHCs) and spiral ganglion neurons (SGNs). This excitotoxic damage can trigger the degradation of the neurotrophic TrkB receptor, thereby inhibiting brain-derived neurotrophic factor (BDNF) signaling and challenging neurotrophin-based therapies for hearing loss. Methods We employed an ex vivo model of excitotoxicity, where excitotoxicity was induced in cochlear explants by overstimulation of excitatory glutamate receptors, and an in vivo model of noise overexposure. The effects of excitotoxicity on the neurotrophic system and cell architecture were established by immunohistochemistry. Hearing function was evaluated in vivo by the auditory brainstem responses (ABR) test, performed before and after noise overexposure. Results In this study, we evaluated the therapeutic potential in the inner ear of MTFL 457 , a cell-penetrating peptide designed to prevent TrkB-FL degradation in brain excitotoxicity. MTFL 457 showed efficient distribution across cochlear cell types in both ex vivo and in vivo models, supporting its ability to reach the inner ear and suggesting that it can cross the blood-labyrinth barrier after systemic administration. In explants undergoing excitotoxicity, MTFL 457 prevented TrkB-FL dysregulation, partially restored downstream prosurvival signaling, and significantly reduced neuronal damage and features associated with cochlear synaptopathy. In vivo, despite known sex-dependent differences in susceptibility to noise-induced damage, treatment with MTFL 457 preserved auditory function and synaptic integrity in both males and females, although the magnitude of protection varied between sexes. Together, these findings support a protective effect of MTFL 457 in models of excitotoxic cochlear injury. Conclusions These results support the therapeutic potential of peptide MTFL 457 for treatment of NIHL and possibly other types of sensorineural hearing loss likewise associated with excitotoxicity.

Age‐related vestibular dysfunction (ARVD) is a prevalent and debilitating condition among the elderly, yet its etiology and underlying molecular mechanisms remain poorly understood. We focused on mechanosensitive hair cells (HCs), which are widely recognized as susceptible to aging. Using single‐cell RNA‐seq transcriptomic analysis of young and old mice, we show that old vestibular HCs exhibit conserved transcriptomic hallmarks of cellular aging, including cellular senescence, mitochondrial dysfunction, and impaired proteostasis, along with prominent cell type‐specific changes linked to hair bundle architecture and the mechanotransduction machinery. Consistent with these transcriptomic findings, imaging and electrophysiological recordings from old vestibular sensory epithelia reveal hair bundle degeneration and reduced mechanotransduction activity. Importantly, this structural and functional deterioration precedes HC loss, underscoring impaired hair bundle function as a key driver of ARVD. Furthermore, our comparative analysis identifies both shared and distinct aging signatures in vestibular and cochlear HCs, providing broader insight into the mechanisms that may underlie their different rates of age‐related degeneration.

Exposure to stress can cause long-lasting enhancement of fear and other defensive responses that extend beyond the cues or contexts associated with the original traumatic event. These nonassociative consequences of stress, referred to as fear sensitization, are thought to underlie some symptoms of trauma-related disorders. Fear sensitization has been predominantly studied using the stress-enhanced fear learning (SEFL) paradigm, which models the stress-induced amplification of fear learning. Less is known about the mechanisms through which unlearned fear responses are sensitized by stress. Here, we investigated the neural mechanisms for sensitization of unlearned fear responses using a paradigm we termed stress-enhanced fear responding (SEFR). In this model, mice exposed to a single session of footshock stress exhibit enhanced freezing to a novel tone stimulus. To investigate brain regions that might mediate SEFR, we first used c-Fos mapping to identify neural activity changes associated with stress-induced enhancement of unlearned fear. Our c-Fos screen identified the posterior paraventricular thalamus (pPVT) as a region that was persistently hyperactive after footshock stress and whose activity correlated with behavioral expression of SEFR. Using fiber photometry, we observed that SEFR, but not SEFL, was associated with increased activity in the pPVT. Next, we found that chemogenetic inhibition of the pPVT blocked both the induction of SEFR during stress and its later expression, while artificial stimulation of pPVT in stress-naive mice was sufficient to recapitulate SEFR. Interestingly, pPVT inhibition or stimulation did not affect acquisition or expression of SEFL. In conclusion, our results indicate that sensitization of fear learning (SEFL) and sensitization of unlearned fear (SEFR) have distinct neural mechanisms. Our results identify pPVT hyperactivity as a mechanism for stress-induced sensitization of unlearned fear and highlight pPVT as a potential target for treating arousal and reactivity symptoms of trauma- and stressor-related disorders.

Background Iron is a key nutrient for the development of the fetal auditory system. However, the potential impact of non-anemic prenatal iron deficiency (ID) on neonatal auditory function remains unclear. This study aimed to systematically explore the potential mechanisms by which maternal ID may affect auditory maturation of offspring. Methods We analyzed population data from 696 mother–infant pairs, established ID mouse models (C57BL/6 J) during pregnancy, and conducted cellular experiments. Results In the human cohort, maternal serum ferritin (SF) and hemoglobin (Hb) were significantly negatively associated with the latency (ms) of auditory brainstem response (ABR) waves I, III, and V, as well as intervals (ms) of waves I–III, III–V, and I–V and summating potential/action potential ratios (%). Neonatal SF partially mediated the association between maternal iron status and auditory function, with mediation effects ranging from 28.57 to 76.32%. In mouse models, prenatal ID was associated with decreased wave I amplitude and extended latency in offspring, along with reduced ribbon synapses in inner hair cells, mitochondrial damage, and decreased enzyme activity in supporting cells. A metabolomics analysis revealed significant downregulation of pyruvate levels in the ID group, and exogenous supplementation with sodium pyruvate partially restored ribbon synaptic function. Collectively, prenatal ID may reduce fetal iron reserves, impair energy metabolism of cochlear supporting cells, inhibit ribbon synaptic maturation, and potentially contribute to auditory dysfunction. Conclusion Our findings suggest that non-anemic maternal ID may be associated with delayed neonatal auditory maturation, highlighting the potential importance of iron intervention during pregnancy for improving neonatal auditory outcomes; however, causal relationships cannot be established from the observational human data, and the animal/cellular findings should be interpreted as supportive evidence requiring further validation.

Hearing impairment is attributed to factors such as age, genetic predisposition, and environmental influences, among which environmental factors are considered modifiable. Among various environmental factors, the role of poor lifestyle habits is particularly critical, yet the specific mechanisms by which they contribute to hearing damage remain unclear. This study reveals that dysregulated hormone levels due to disrupted light exposure may significantly increase susceptibility to sensorineural hearing loss. In mice, circadian rhythm disruption was found to reduce melatonin and elevate serotonin levels in the inner ear, thereby increasing vulnerability to cisplatin‐induced ototoxicity. In both in vivo and in vitro cisplatin‐treatment models, we showed that combined treatment with melatonin protected hearing, reduced inner ear cell death, and preserved synaptic connections, whereas serotonin co‐administration exacerbated the damage. Using small molecule–protein interaction prediction, we identified NOS3 as a potential target of both melatonin and serotonin, through which they appear to regulate the NO signaling pathway and influence hair cell ferroptosis. Finally, exogenous supplementation of NOS3 in cochlear tissues effectively mitigated cisplatin‐induced hair cell damage, even under conditions of circadian rhythm disruption. These findings indicate that the melatonin/serotonin balance modulates susceptibility to sensorineural hearing loss via the NOS3–NO signaling pathway.

Objective To evaluate the feasibility of using the acoustic change complex (ACC) as an objective cortical marker of continuous speech sound discrimination using connected Ling-six stimuli. Design Cortical auditory evoked potentials were recorded from 10 young adults with normal hearing using a continuous, pause-free sequence of the six Ling phonemes (/u-a-i-ʃ-s-m/). ACC responses were recorded in a passive listening paradigm with minimal electrodes. Reproducibility was assessed in a subset of participants retested 1 year later. Results Robust ACC responses were elicited for all six phonemic transitions in every participant, indicating reliable cortical discrimination within the continuous speech stream. Although response morphology varied across listeners, within-subject responses demonstrated strong reproducibility over a one-year interval (mean cross-correlation = 0.95). Conclusion Continuous Ling-six stimuli reliably evoke ACC responses reflecting cortical speech sound discrimination. This efficient and repeatable paradigm shows promise as an objective verification tool for auditory learning and sound discrimination, particularly in populations for whom behavioral assessment is unreliable.

Noise-induced hearing loss (NIHL) is a major form of sensorineural hearing impairment driven by oxidative stress-mediated cochlear injury. Sanghuangporus sanghuang (SS), a medicinal fungus extensively studied in microbiology and biotechnology, is known to produce bioactive metabolites with antioxidant properties; however, its functional role in the auditory system has not been established. This study investigated the otoprotective potential of SS extract against oxidative and acoustic stress using complementary in vitro, ex vivo, and in vivo models. In H2O2-treated UB-OC1 auditory cells, SS (25-200 μg/mL) dose-dependently restored cell viability and significantly reduced intracellular reactive oxygen species accumulation. Western blot analysis demonstrated that SS suppressed the expression of apoptotic markers, including cleaved caspase-3 and cytochrome C. At the molecular level, SS upregulated Nrf2 and HO-1 expression at both mRNA and protein levels, without a significant change in Keap1 expression, indicating activation of endogenous antioxidant defense via the Nrf2/HO-1 signaling axis. Consequently, downstream antioxidant genes such as SOD1 and NQO1 were significantly upregulated. In ex vivo cochlear explant cultures, SS preserved hair cell integrity against H2O2-induced damage, as confirmed by phalloidin staining. In a murine NIHL model, oral administration of SS attenuated ABR threshold shifts, maintained Wave I amplitudes, and preserved the structural organization of outer hair cells across all cochlear turns. Collectively, these findings demonstrate that SS confers otoprotection by modulating the Nrf2/HO-1 antioxidant axis and mitigating oxidative stress-induced sensory cell injury, supporting the potential of SS as a fungal-derived functional bioactive resource for redox-associated cochlear protection.

Purpose: The UmboMic is a recently developed middle ear microphone that functions by detecting the sound-induced motion of the umbo [1]. To prepare for a live animal study of the in vivo performance of the UmboMic, we developed the surgical implantation and fixation system in cadaveric sheep ears. Methods: Temporal bones from seven female sheep were prepared for implantation of the UmboMic system. Fixation hardware for sheep was designed to secure the UmboMic sensor in position so that the sensing tip contacted the umbo in the middle-ear cavity and the non-sensing tail end was secured to the surrounding mastoid bone. First, pre-surgical micro-CT scans of the temporal bones and open-source software were used to simulate surgical drilling, and to virtually plan and fit the UmboMic fixation system. Then, in physical sheep temporal bones, sound-induced umbo motion was measured with a laser Doppler vibrometer as a preliminary step. After surgical implantation of the UmboMic system, the position of the UmboMic sensor was evaluated with microscopic visualization and post-surgical micro-CT. Implanted UmboMic sensor function in response to acoustic frequency sweeps to the external ear canal was measured in two specimens. Results: Measurements of sheep temporal bone anatomical dimensions with micro-CT showed that the facial recess featured a mean maximum height of 2.36 mm, length of 12.2 mm, and depth from outer opening surface of facial recess to the umbo of 11.1 mm. The amplitude of umbo motion prior to UmboMic implantation was consistent with that previously reported by [2], with a displacement of ~ 14 nm/Pa up to a frequency of 5.5 kHz, followed by a gradual drop-off. When bench tested and implanted in sheep temporal bones, the UmboMic sensitivity was as predicted from [1], ~ 1-2 fC/nm. Conclusion: When implanted in sheep cadaveric ears, UmboMic performance was similar to previous measurements in fresh human cadaveric temporal bones. The method of simulating surgical drilling using micro-CT and simple open-source software is economical and broadly applicable in understanding the 3D biological anatomy and implantable device design and customization. The UmboMic implantation in cadaveric sheep ears was possible, and this study represents a step towards planned live animal studies.

CLN3 disease, the most common form of the Neuronal Ceroid Lipofuscinoses (NCLs), causes progressive cognitive decline and language impairment in humans. A pathological hallmark is the accumulation of storage material within neuronal lysosomes resulting from mutations in the CLN3 gene. We previously identified parallel deficits in auditory duration mismatch negativity (MMN), an electroencephalography (EEG)-based marker of auditory change detection, in individuals with CLN3 disease and in Cln3 -/- mice. MMN-dependent auditory change detection relies on sensory-memory comparison mechanisms. However, the anatomical and neurophysiological substrates underlying this response in CLN3 disease remain unclear. Here, we investigated central auditory dysfunction in Cln3 -/- mice by integrating immunohistochemical mapping of lysosomal storage pathology, using the canonical marker Subunit C of Mitochondrial ATP Synthase (SCMAS), with EEG analysis of auditory evoked potentials (AEPs). Neuropathological analyses revealed age-dependent and sex-divergent SCMAS accumulation across the auditory thalamocortical circuit, including the excitatory auditory thalamus, the inhibitory thalamic reticular nucleus, and the primary auditory cortex. In parallel, Cln3 -/- mice exhibited age- and sex-dependent alterations in AEPs relative to wild-type controls. Importantly, an integrated measure of auditory thalamocortical SCMAS accumulation accounted for a substantial portion of age- and sex-matched variation in AEP responses, with stronger associations for the early N1 component than the later MMN component. Together, these findings link age-dependent and sex-divergent auditory neurophysiological deficits to region-specific lysosomal storage pathology within the auditory thalamocortical circuit in the Cln3 -/- mouse model. This integrated functional-anatomical framework provides insight into circuit vulnerability and supports the development of translational neurophysiological biomarkers for CLN3 disease. Graphical Abstract Highlights SCMAS accumulates across the auditory thalamocortical circuit in Cln3 -/- mice Accumulation shows distinct age- and sex-dependent regional trajectories Cln3 -/- mice exhibit progressive alterations in auditory evoked potentials Thalamic pathology is strongly associated with the early auditory N1 response Histology–EEG integration links circuit pathology to auditory dysfunction

Mutations in Myo7a cause Usher syndrome type 1B and non-syndromic deafness, but the precise function of MYO7A in sensory hair cells remains unclear. Using long-read sequencing, we identify and characterize a novel isoform, MYO7A-N, expressed in auditory hair cells alongside the canonical MYO7A-C. Isoform-specific knock-in mouse models reveal that inner hair cells primarily express MYO7A-C, while outer hair cells express both isoforms in opposing tonotopic gradients. Both isoforms are localized to the upper tip-link insertion site, consistent with a role in the tip link for mechanotransduction. Loss of MYO7A-N leads to outer hair cell degeneration and progressive hearing loss. Cryo-EM structures reveal isoform-specific differences at actomyosin interfaces, correlating with distinct ATPase activities. These findings reveal an unexpected layer of molecular diversity within the mechanotransduction machinery. We propose that MYO7A isoform specialization enables fine-tuning of tip-link tension, thus hearing sensitivity, and contributes to the frequency-resolving power of the cochlea.

Acetylcholine (ACh) release from the basal forebrain has traditionally been viewed as a slow, spatially diffuse signal regulating cortical arousal across sleep and wakefulness 1–3 . Recent characterizations with higher resolution optical sensors have revealed rapid, local cholinergic modulation supporting dynamic changes in sensory processing, associative learning, and behavioral state 4–7 . However, sensory events that recruit cortical ACh often also change arousal and evoke movements, making it difficult to determine whether ACh transients reflect sensory features of environmental stimuli or the behavioral state changes that accompany sensory stimulation. To separate these contributions, we performed optic fiber recordings of a genetically encoded ACh fluorescent sensor in the auditory, visual, and prefrontal cortex of awake, head-fixed mice while monitoring pupil size and facial movements. Across cortical areas, ACh release tracked spontaneous fluctuations in arousal state, as indexed by pupil dilation and orofacial movements. Sensory stimuli also evoked rapid ACh transients, with sounds producing larger and more widespread responses than visual stimuli. Because sounds also elicited time-locked pupil dilations and facial movements, we used multivariate modeling to estimate the relative contributions of stimulus features, arousal, and behavior to cortical ACh dynamics. We identified a regional dissociation: sound-evoked ACh release in prefrontal cortex was largely explained by arousal- and movement-related variables, whereas auditory cortical ACh release retained a stronger relationship to stimulus features. These findings show that cortical ACh signaling reflects both shared arousal state and area-specific sensory processing and demonstrate that sound is especially effective at recruiting rapid, widespread cholinergic modulation across cortex.

Auditory brainstem response (ABR) recordings are widely used in neuroscience as a cross-species translational tool to evaluate hearing sensitivity and auditory processing. In animal models, ABR recordings typically require the use of anesthesia to minimize myogenic artifacts, necessitating the development of anesthetic regimens that balance safety, adequate immobilization, and preservation of neural responses. Using a within-subject design in male and female Long-Evans rats, this study systematically evaluated the safety and auditory signal fidelity of five anesthetic regimens -ketamine/xylazine (K/X), ketamine/dexmedetomidine (K/D), dexmedetomidine alone (DEX), dexmedetomidine plus low dose (0.5%) isoflurane (D/I), and high dose (2%) isoflurane (ISO). Anesthetic safety and efficacy were assessed by induction time, recovery time, blood oxygen saturation (SpO₂), and survival rate. ABR signal quality was quantified by threshold, signal strength, wave amplitude, wave latency, and inter-trial phase coherence. K/X anesthesia produced ABRs with low thresholds and well-defined waveforms, but also exhibited the least favorable safety profile, with prolonged recovery times and reduced survival rates. Conversely, isoflurane regimens (ISO and D/I) had a favorable safety profile but significantly elevated thresholds and degraded ABR signal quality, even at low doses. K/D and DEX achieved survival and recovery outcomes equal to or better than conventional anesthetics (K/X and ISO) while also preserving ABR waveform morphology and trial-to-trial reliability. Together, these results highlight dexmedetomidine, particularly when combined with ketamine, as a safe and effective anesthetic for ABR recordings that preserves key metrics of auditory sensitivity and signal integrity.

Kanamycin (KM), a widely used aminoglycoside antibiotic, is limited by its ototoxic side effects, primarily targeting cochlear outer hair cells (OHCs) and leading to irreversible sensorineural hearing loss. Our previous work showed that silencing AMP‐activated protein kinase alpha 1 (AMPKα1) prevents noise‐induced hearing loss through a redox‐sensitive regulatory mechanism. Given that both noise‐induced and aminoglycoside‐induced hearing loss share oxidative stress as a key pathological feature, we tested whether AMPKα1 silencing could mitigate KM‐induced damage using an acute ototoxic model combining KM with furosemide (KM + FU). KM + FU exposure markedly increased AMPKα phosphorylation at Thr172. Targeted siRNA‐mediated silencing via posterior semicircular canal delivery in CBA/J mice significantly reduced AMPKα1 expression in OHCs and effectively prevented KM + FU‐induced OHC loss and hearing impairment. This preventive effect was independent of stria vascularis permeability or cochlear KM uptake. These findings identify AMPKα as a contributor to KM + FU‐induced acute ototoxicity and suggest that its inhibition may be a promising strategy for hearing preservation.

We describe properties and laminar organization of visual and auditory responses sampled with linear electrode arrays in and around the supplementary eye field of four macaque monkeys performing a visually guided task with a tone secondary reinforcer. Of pyramidal neurons in all layers and interneurons in L3 and L5/6, one-quarter were visually responsive, one-quarter, auditory, with 30% bimodal. Visual neurons were less common rostral, lateral, and medial to the supplementary eye field. Facilitated visual and auditory responses were much more common than suppressed. Pyramidal and interneurons responded to the stimulus in either hemifield with a weak bias for contralateral targets. Visual response latencies were comparable to values previously reported and later than auditory responses. Facilitated visual responses of interneurons preceded those of pyramidal neurons. Transient visual responses preceded sustained. Current-source density revealed visually evoked current sinks after auditory sinks that were transient for bright flashes and prolonged for the discrete task target. The earliest sink appeared at the L3 to L5 border and spread superficially and deeper with idiosyncratic variability across monkeys. These findings reveal new details about sensory processing in medial frontal cortex and complement our previous descriptions of the functional properties and laminar organization of neurons supporting cognitive control.

Optical coherence tomography has allowed in vivo recording of sound-induced vibrations of different regions within the organ of Corti complex (OCC), including the basilar membrane (BM), outer hair cell/Deiters cell (OHC/DC) region, and reticular lamina (RL). In the hook region of the gerbil cochlea, where measurements can be made with a predominantly transverse optical axis, the three regions have different and characteristic motion responses: The OHC/DC region has greater motions than the other two regions at frequencies below the best frequency (sub-BF); the RL region typically has the greatest BF peak and smallest sub-BF motion. The phase of the OHC/DC-region motion increasingly lags BM motion phase as frequency increases; the RL-region motion phase leads BM, but with a relatively small value. All three regions are compressively nonlinear in the BF peak, but only the OHC/DC region shows sub-BF compressive nonlinearity. Here, we describe the strains that arise when the motion transitions between these regions. Large strains (deformations) were observed in the OHC body close to the RL. A region of large strain can be as short as a single 2.7-μm measurement pixel, or it can extend over several pixels, with extensive strains appearing more often at 70 than at 50 dB sound pressure level. Beyond this RL region of large strain, over a distance that can exceed 20 μm, the OHC/DC region displayed nearly spatially unvarying motion; this region vibrated as a relatively rigid body. And beyond this, at sub-BF frequencies, another region of high strain was present, indicating stretching/compressing or bowing/tilting of the DC microtubular stalk.

Objectives. This study aimed to explore the role of the Pcdh15 gene in hearing maintenance and to examine the effects of its deficiency on cochlear structure, cochlear function, and hearing loss in mice.Methods. CRISPR/Cas9 technology was used to generate Pcdh15 knockout (KO) mice. Auditory function was evaluated using hearing tests, while histological approaches were employed to assess morphological changes in cochlear hair cells and spiral ganglion neurons (SGNs). RNA sequencing (RNA-seq) was performed on cochlear tissue from postnatal day 18 (P18) wild-type (WT) and Pcdh15 KO mice to identify differentially expressed genes (DEGs). These DEGs were subjected to functional annotation and pathway analysis, with particular emphasis on oxidative phosphorylation (OXPHOS). Reactive oxygen species (ROS) levels were quantified using flow cytometry and DCFH-DA assays.Results. Pcdh15 KO mice exhibited progressive sensorineural hearing loss, which worsened to profound deafness by P18. Notably, cochlear hair cells and SGNs showed substantial loss and pronounced morphological abnormalities, particularly within the basal high-frequency region. RNA-seq analysis identified 1,359 DEGs, including 1,024 downregulated and 335 upregulated genes. Pathway analysis indicated that Pcdh15 deficiency was associated with inhibition of the OXPHOS pathway, potentially disrupting mitochondrial respiratory chain complexes I, III, IV, and V and thereby impairing energy production and ATP metabolism. In addition, early-stage cochleae from KO mice demonstrated elevated ROS levels and increased oxidative stress, suggesting that redox imbalance may contribute to hearing damage.Conclusion. Pcdh15 plays a critical role in hearing maintenance. Its deficiency is associated with severe hearing loss and marked cochlear abnormalities, which are linked to inhibition of OXPHOS, disruption of energy metabolism, and exacerbation of oxidative stress. Together, these findings provide new insights into the mechanisms underlying hearing loss and suggest potential targets for therapeutic intervention.

Background Stem cell therapy offers promise for the neurodegenerative diseases and has been explored for sensorineural hearing loss (SNHL). However, effective cell delivery strategies remain a critical challenge for SNHL treatment. Methods To address this need, we established an ouabain‐induced SGN injured hearing loss model in rat and evaluated a novel transplantation strategy targeting the cochlear nerve surface via posterior occipital approach, designed to minimize cochlear structural damage and facilitate targeted cell delivery to Rosenthal's canal (RC). The temporal changes in glial cell densities within RC revealed a progressively deteriorating neural microenvironment, supporting early‐stage intervention. Accordingly, hair follicle‐derived neural crest stem cell (HFNCSC) transplantation was performed 3 or 4 days after modeling via two approaches: cochlear nerve surface transplantation (CNT) and round window transplantation (RWT). Results CNT resulted in significant improvements in auditory function, as evidenced by reduced auditory brainstem response (ABR) thresholds, shortened wave I latencies, and preserved wave I amplitudes post‐transplantation. Transplanted cells were distributed along the nerve trunk and within RC. In contrast, RWT failed to improve auditory function and caused cochlear structural damage, with widespread cell dispersion in cochlear fluids. Notably, the CNT group exhibited significantly higher densities of TUJ1‐positive neuron‐like cells and glial cells in the RC, accompanied by enhanced myelin basic protein expression suggestive of remyelination. No such improvements were observed in the RWT group. Conclusions These findings suggest that cochlear nerve surface transplantation enhances stem cell survival and auditory function recovery, and represents a promising delivery approach for stem cell‐based therapy of SGN‐related hearing loss.

Perceptual entrainment and temporal prediction aid speech perception in both quiet and noisy environments. Isochronous, periodic auditory rhythmic cues facilitate neural entrainment and temporal expectations which can benefit encoding and perception of target speech. However, most studies using isochronous cues confound periodicity with predictability. To this end, we characterized how systematic changes in the acoustic dimensions of stimulus rate, target phase, periodicity, and predictably of an entraining sound precursor impact the subsequent identification of concurrent speech targets. Target concurrent vowel pairs were preceded by rhythmic woodblock cues which were either periodic-predictable (PP, isochronous rhythm), aperiodic-predictable (AP, accelerating rhythm), or aperiodic-unpredictable (AU, random rhythm). The number of pulses per rhythm was roved to further manipulate predictability. Stimuli also varied in presentation rate (2.5, 4.5, 6.5 Hz) and target speech phase (in-phase, 0°; out-of-phase, –90°, 180°) relative to the preceding entraining rhythm. We also measured participants’ musical pulse continuation and standardized speech-in-noise perception abilities. We did not observe any effects of stimulus rhythm, rate, or target phase on target speech identification accuracy. However, reaction times were slowest at the nominal speech rate (4.5 Hz) and were most disrupted by out-of-phase presentations following the PP rhythm. Double-vowel task performance was associated with stronger musical pulse continuation abilities, but not speech-in-noise perception. Our results support the notion that perceptual entrainment benefits from rhythmic cues rely on top-down processing and thus are relatively muted when stimulus predictability is unknown. Additionally, we find that individual differences in musical pulse perception may underlie benefits of rhythmic cueing on subsequent speech perception.