Auditory Research publications

The inferior colliculus (IC) is a major midbrain convergence site critical for processing complex sounds and undergoes fundamental changes with age-related hearing loss (ARHL). Local field potentials (LFPs) represent pre-synaptic integration of excitatory and inhibitory signals in local neural populations. Here, we assessed age-related changes in sound-evoked IC LFPs in the CBA/CaJ mouse model of ARHL across the tonotopic axis. We recorded from 495 sites across four age groups (young: 4-6 months; middle: 8-14 months; old: 24-25 months; “oldest old”: 27-31 months), examining LFP responses from dorsal (low-frequency), medial (mid-frequency), and ventral (high-frequency) IC regions. Analysis of the onset depolarization (N1 component) in response to broadband noise bursts revealed significant age-related hyperexcitability in medial and dorsal regions, with oldest old animals showing enhanced responses while ventral regions were unaffected. Amplitude-intensity functions demonstrated significant age × level interactions across all regions, with oldest old animals exhibiting level-dependent hyperexcitability most pronounced at suprathreshold intensities. Time-frequency analysis of LFP spectral content (30-100 Hz) revealed a crossover pattern across medial and dorsal regions, with oldest old animals showing reduced power at low-to-moderate stimulus levels but enhanced power at high stimulus levels. Ventral regions showed a low-level reduction without suprathreshold enhancement. These findings reveal paradoxical enhancement of neural activity in the aging IC, with the most pronounced changes in dorsal and medial regions rather than ventral regions most affected by peripheral hearing loss, suggesting that central hyperexcitability depends on residual afferent drive and implicating region-specific alterations in excitatory-inhibitory balance underlying central presbycusis.

Auditory hypersensitivity or decreased sound tolerance is a common phenotype of Fragile X Syndrome (FXS). Impairments in adaptation, defined as the reduction in the neuronal responsiveness to repeating sounds, can contribute to this prevalent phenotype. Previous studies on event-related potential observed impairments in mismatch negativity (MMN) in both FXS individuals and in the FMR1 -knockout (KO) mouse model of FXS. Therefore, in the present study we characterized stimulus-specific adaptation (SSA), a neural correlate of MMN, at the auditory cortex (AC) of anesthetized (with ketamine/xylazine) female and male postnatal day 20 (P20) wild-type (WT) and FMR1 -KO mice, using the oddball paradigm with either 4 Hz or 1 Hz repetition rate. We observed robust SSA at the 4 Hz repetition rate of the oddball paradigm in the AC neurons of all four groups of animals. We also noted that the strength of SSA diminished between 4 to 1 Hz repetition rate. In addition, at both the 4 Hz and 1 Hz repetition rate, reduced SSA was observed particularly in the male FMR1 -KO mice compared to their WT counterparts, while female WT and FMR1 -KO mice displayed similar SSA. In terms of sex differences, male FMR1 -KO mice had lower SSA than female FMR1 -KO mice, while SSA was similar in male and female WT mice. Overall, our observation of reduced SSA in the male FMR1 -KO mice suggests that impairments in neuronal adaptation potentially contribute to the auditory hypersensitivity phenotype particularly within the male population.

The brain computes sound location from auditory spatial cues. Humans and barn owls both localize sounds accurately, yet they rely on fundamentally different cue configurations shaped by their ear anatomy and neural circuitry. In humans, symmetrical ears provide interaural time and level differences (ITD and ILD) for horizontal localization, while vertical localization depends primarily on high‐frequency, monaural spectral cues generated by the pinnae. Barn owls, by contrast, possess asymmetrical ears and use binaural cues for both azimuth and elevation. Because auditory pathways are tuned to species‐specific cue statistics, it remains unclear whether humans can adapt when binaural level cues are also made informative about elevation. We tested this by fitting human listeners with asymmetric ear molds that disrupted normal spectral cues, introduced elevation‐dependent ILDs, and left ITDs unaffected. Participants wore the molds during daily life and were tested with broadband, high‐pass, and low‐pass noise bursts. Acute mold exposure severely degraded elevation localization, whereas horizontal localization remained largely unaffected. With prolonged exposure, elevation localization improved, but adaptation was limited, variable across listeners, and fluctuated across sessions. Improvement was strongest for broadband sounds. Because broadband and high‐pass sounds both contained high‐frequency information, this broadband advantage cannot be explained by access to additional spectral cues alone. Instead, it suggests that low‐frequency ITDs helped listeners exploit the altered binaural cue structure, including the elevation‐dependent ILDs introduced by the molds. These findings show that humans can partially adapt to asymmetric outer‐ear acoustics when complementary spatial cues help resolve ambiguity in the altered cue structure.

Background Peripheral hearing loss is associated with auditory hallucinations and increased risk for psychotic disorder, particularly in genetically vulnerable individuals. Moreover, both hearing loss and schizophrenia disrupt auditory temporal acuity, a sensitive measure of auditory brain function. Here, we used mouse models of hearing loss and schizophrenia to reveal how neural mechanisms of auditory cortical temporal acuity depend on sensory and genetic risk factors for psychosis. Methods We quantified auditory cortical temporal acuity in mice with or without hearing loss and with or without the 22q11.2 deletion — one of the strongest known genetic risk factors for schizophrenia. Cortical single-unit and population activity were recorded in awake mice (N = 23) during presentations of loudness-adjusted gap-in-noise stimuli with varying durations of silent gap, which are commonly used to assess auditory temporal acuity in humans. Results Both hearing loss and the 22q11.2 deletion disrupted auditory cortical temporal acuity, but through distinct mechanisms. Hearing loss broadly degraded temporal acuity at the level of single-unit responses and neural population activity. In contrast, the 22q11.2 deletion selectively impaired gap duration thresholds in regular-spiking (putative excitatory) but not fast-spiking (putative inhibitory) neurons. Mice with comorbid hearing loss and 22q11.2 deletion exhibited both abnormalities in auditory cortical temporal acuity. Conclusions Sensory and genetic risk factors for psychosis can disrupt auditory cortical temporal acuity via distinct mechanisms that remain partially dissociable even under comorbid conditions. These findings underscore the importance of accounting for hearing loss comorbidity when interpreting auditory cortical dysfunction in psychotic disorder.

Humans localise sounds in the horizontal plane by processing level and timing differences between the ears. This neurocomputational process is continuously and adaptively calibrated using visual input, as seen in the ventriloquism aftereffect: a shift in sound perception toward a previously seen light. It is unknown from where in the brain this aftereffect originates; adaptation could occur at an early level in the auditory system where neurons are narrowly tuned to frequency, at a later level in the auditory system where localisation cues are extracted, or outside the auditory system at a higher-level spatial map. To investigate this, we examined how the ventriloquism aftereffect generalises across sound frequencies. Participants localised seven narrowband sounds (0.5–8 kHz), targeting different localisation cues. We found that sound localisation accuracy in darkness varied slightly with frequency. When sounds were paired with a visual stimulus that was offset by 10 deg, participants exhibited a pronounced bias toward the light of about ~ 63%, corresponding to the well-known ventriloquism effect. The bias was stronger for narrowband compared to broadband sounds. After exposure to a block of these audiovisual stimuli, a ventriloquism aftereffect in the form of a spatial bias of ~ 12% was observed across all tested frequencies, largely independent of the frequency of the exposure sound. Together with earlier reports of both frequency-specific and frequency-general recalibration, our results indicate that under conditions of a fixed and consistent audiovisual spatial offset, the ventriloquism aftereffect generalises across sound frequencies, consistent with adaptation at a frequency-independent multisensory spatial stage.

Prairie voles ( Microtus ochrogaster ) are a semi-fossorial rodent that are an emerging model in social neuroscience. Comparing laboratory-reared and wild-caught individuals is essential for understanding how environmental history shapes neural and sensory traits and for assessing the ecological validity of laboratory findings. Despite this, relatively few studies have taken this approach. We used auditory brainstem responses (ABRs) to compare ABR thresholds and ABR wave characteristics between laboratory-reared and wild-caught prairie voles. ABR recordings show that, similar to other semi-fossorial rodents, M. ochrogaster exhibit a hearing range of 1–46 kHz with peak sensitivity between 8–24 kHz in wild-caught and 8–32 kHz in laboratory-reared voles. However, wild-caught prairie voles displayed significantly lower ABR thresholds at 1, 4, 8, 16, and 24 kHz compared to laboratory-reared prairie voles. There were significant differences in interpeak latency between both tested groups, with laboratory-reared prairie voles showing faster interpeak latency responses than wild-caught voles. However, there were no differences in amplitude ratios between groups. Laboratory-reared prairie voles showed faster normalized latencies and higher relative amplitude of the binaural interaction component (BIC) of the ABR than wild-caught voles. There were no significant differences in ABR thresholds, interpeak latency, amplitude ratio, normalized latency, and relative amplitude between the sexes. These differences in auditory processing support the importance of integrating both wild and captive populations to advance comparative auditory research.

Binaural cues are crucial for sound localization, and understanding the neural mechanisms of binaural sound processing gives important insights into how receivers localize signalers, which in anurans is a key component of mate selection. We characterized the binaural interaction component (BIC) by collecting monaural and binaural auditory brainstem responses (ABR) using click stimuli with varying interaural time difference (ITD) and interaural level difference (ILD) in male and female Cope’s gray treefrogs ( Hyla chrysoscelis ). We hypothesized that the latency of the BIC peaks would increase with larger ITDs and ILDs. We also hypothesized that females would show a stronger relationship between binaural cues and BIC characteristics than males because of the greater importance of directional hearing for females. We characterized two prominent BIC peaks, DN1 and DN2. Both BIC peak latencies had a positive relationship with ITD, but there was no effect of ITD on peak amplitudes. The amplitude and latency of the BIC peaks were not affected by variation in ILD. There were no sex or body size effects on ABR characteristics including BIC characteristics or the effects of ITD or ILD on the BIC. Our findings demonstrate that the BIC is driven primarily by ITD in H. chrysoscelis . This is the first study to characterize the BIC in an amphibian, which expands the comparative understanding of the neural mechanisms of binaural hearing in vertebrates.

This work presents three open datasets featuring various levels of processing, containing neural recordings from the auditory cortex of rats. These recordings were obtained during experiments using the auditory oddball paradigm before, during and after the local microiontophoretic application of acetylcholine. The primary objective of these datasets is to investigate how the brain processes predictable versus unexpected auditory stimuli, and the role of cholinergic inputs during such processing. The data include multi-unit recordings of neuronal activity during the presentation of standard and deviant tones, classified by stimulus type and cortical sub-region. These resources enable quantitative investigations of deviance detection, stimulus-specific adaptation, cholinergic modulation and predictive-coding mechanisms at multiple temporal scales.

Autism is an early‐onset neurodevelopmental disorder characterized by restricted, repetitive behaviors and atypical patterns of social communication and interaction. A considerable proportion of autistic individuals experience divergent auditory perception, which can interfere with their ability to navigate everyday sound environments. Auditory brainstem responses are electrophysiological potentials elicited by auditory stimuli that evaluate neural activity along the auditory nerve and brainstem. Importantly, the auditory brainstem response varies by sex, with females typically showing higher amplitudes and shorter latencies than males. This sex‐specific neurophysiological profile is especially relevant in autism research, where the male‐to‐female diagnosis ratio is approximately 3:1. Thus, exploring the neurobiological mechanisms underlying sex‐specific variations in autistic traits is essential. Furthermore, autism sensory profiles may vary based on the independent and mutual effects of environmental and genetic factors. To deepen this understanding, we examined auditory brainstem responses in two rat models of autism: the GRIN2B rare mutation model and the prenatal valproic acid induction model, alongside control animals. We assessed peak amplitudes and latencies (Waves I through V), inter‐peak intervals (I–III, I–V, and III–V), and amplitude ratios (III:I, V:I, and V:III). Female rats generally exhibited greater amplitudes and longer latencies across waveforms. Regarding rat models, control animals consistently showed larger amplitudes and shorter latencies compared to autism‐like models. Exploratory analyses further suggested pairwise interactions between sex and rat model, indicating modulation of auditory phenotypes linked to autism. Thus, our findings reveal key insights into the effects of sex and rat model, as well as their interactions.

Introduction Prenatal exposure to valproic acid (VPA) is a common environmental cause of autism spectrum disorder (ASD) and often leads to expressive and receptive language impairments. Similar communication difficulties among individuals with ASD are often linked to abnormal subcortical and cortical sound processing. Rodents prenatally exposed to VPA exhibit degraded cortical responses to speech and an impaired ability to behaviorally discriminate speech sounds. Methods We sought to determine whether sound processing could be restored with paired vagus nerve stimulation (VNS). In a first experiment, we evaluated whether sound-paired VNS would alter in vivo extracellular multi-unit responses to tones, noise burst trains, and speech sounds from the anterior auditory field. We next sought to evaluate whether improvements to neural sound processing led to improvements in sound discrimination ability. In a second experiment, rats underwent go/no-go sound discrimination testing where VNS was paired with successful trials. Results We found that VPA-exposed rats had degraded spectral, temporal, and speech sound processing compared to saline-exposed control rats. VPA-exposed rats which received sound-paired VNS exhibited a partial or full restoration of processing across sound types. However, across several sound discrimination tasks, we did not observe changes in behavioral performance in response to prenatal exposure to VPA or VNS. Discussion Our study is the first to show that speech-paired VNS leads to a generalized improvement in cortical sound processing across sound types, rescuing neural processing among VPA-exposed rats. These results provide a framework for future studies to develop VNS-based interventions for communication disorders.

The mediodorsal thalamic nucleus (MD) forms neural circuits with various brain regions, including the prefrontal cortex (PFC), the reticular thalamic nucleus (TRN), and the midbrain reticular nucleus (MRN). However, the specific roles and underlying mechanisms in auditory information processing remain unclear. Here, we perform multi-channel electrophysiological recordings in awake mice to investigate the response patterns of the MD to auditory stimuli, as well as the regulatory effects of PFC, MRN, and TRN inputs. We identify two distinct types of sound-evoked responses. The Phasic-response features a transient burst firing to the stimulus with short latency, rapidly adapting to baseline and corresponding to the onset fluctuation of the local field potential. The Sustained-response is marked by prolonged firing with longer latency and is accompanied by persistent enhancement of oscillatory power following stimulus offset. The response patterns of MD neurons remain consistent across different types of auditory stimuli. Optogenetic inactivation of the MRN suppresses both response types in the MD. The Sustained-response is attenuated by PFC inactivation but enhanced by TRN inactivation, while the Phasic-response remains unaffected by inactivation of either the PFC or TRN. Our findings expand the understanding of the MD's role in sound information integration and auditory cognitive regulation.

In bats, which express a complex vocal repertoire and are considered vocal learners, the frontal auditory field (FAF) is supposedly placed in a frontal cortico‐striatal network for vocal–motor control. The FAF receives input from the auditory cortex (AC) and other auditory nuclei via multiple pathways. However, not much is known about the transition of information on vocalizations from the AC to the FAF. The bat AC consists of different subfields, among which the dorsal fields (dAC) are characterized by precise coding of the temporal envelope of vocalizations. The dAC should, therefore, be a major source of auditory feedback information about self‐produced or perceived vocalizations to the FAF. Our study aimed to investigate the specificity of encoding for different types of vocalizations in FAF and dAC neurons. Using extracellular recordings in anesthetized Phyllostomus discolor , we describe basic response properties in both cortical areas and compare responses to different types of prerecorded vocalizations. The specificity of encoding for different behaviorally relevant call categories and single calls was higher in dAC than in FAF neurons, both in terms of temporal firing patterns and response strength. These findings highlight the importance of the dAC in the neural network for control of vocal communication in bats.

FKBP5 is a 51-Da FK506-binding protein and member of the immunophilin family involved in controlling the signaling of glucocorticoid receptor from the cytosol to nucleus. Fkbp5 has previously been shown to be expressed in murine cochlear tissue, including the organ of Corti (i.e., the sensory epithelium of the cochlea). Fkbp5-/- mice as used in this study show hearing loss in the low-frequency (8-kHz) range and click-evoked auditory brainstem response (ABR) threshold compared to wild-type mice. Both Fkbp5-/- and wild-type mice showed hearing loss at all frequencies and click-ABR thresholds at 24 h and 14 days following acoustic overexposure (AO). Tissues of the organ of Corti were subjected to RNA sequencing and KEGG pathway analysis. In Fkbp5-/- mice before AO, the mitogen-activated protein kinase (MAPK) signaling pathway was dysregulated compared to wild-type mice. In wild-type mice at 12 h following AO, the most significantly modulated KEGG pathway was the TNF signaling pathway and major MAPK molecules p38 and Jun were involved in the TNF signaling pathway. In Fkbp5-/- mice at 12 h following AO, the MAPK signaling pathway was dysregulated compared to wild-type mice following AO. In conclusion, Fkbp5 interacts with MAPK signaling in the organ of Corti in mice cochleae.

Noise exposure is one of the most common causes of hearing loss and hyperacusis. Studies have shown that noise exposure can induce a cortical gain to compensate for reduced input of the cochlea, which may contribute to the increased sound sensitivity. However, many people with hyperacusis have no measurable cochlear lesion after being exposed to loud sound. In this experiment, we studied the neurological alterations in the cortical and subcortical areas following a prolonged moderate level of noise exposure (84 dB SPL, 8 h/day for 4 weeks) in the laboratory mice. The cochlear function was monitored by auditory brainstem responses (ABRs). The behavioral auditory sensitivity and temporal processing were evaluated using the acoustic startle response (ASR) and gap‐induced prepulse inhibition (gap‐PPI). The central auditory functions were determined by electrophysiological recordings of the inferior colliculus (IC) and the auditory cortex (AC). Our results showed that although there was no significant difference in the ABR thresholds, the noise group showed enhanced ASR and gap‐PPI compared to the control group. Increased neural activity in both the IC and the AC was recorded in the noise‐exposed mice compared to the control group, suggesting a central gain in both the subcortical and cortical regions. The current source density (CSD) analysis of the AC response revealed an increased columnar excitation and reduced corticocortical projection in the noise group, different from the central gain model of noise‐induced hearing loss. Our results suggest that chronic “nondestructive” noise can increase the gain of the central auditory system by altering the balance of auditory thalamocortical and intracortical inputs, which may contribute to the increased sound sensitivity in people with normal hearing.

The hispid pocket mouse ( C. hispidus ) is a solitary semi-fossorial rodent that has been the subject of various ecological and genetic studies. However, no previous studies have characterized its hearing ability, which is important for its survival and fitness. We collected auditory brainstem responses (ABRs) from C. hispidus and measured craniofacial and pinna morphological features to assess hearing ability and test differences in hearing thresholds, monaural and binaural ABR amplitudes and latencies between the sexes. ABR recordings revealed that similar to other small mammals, C. hispidus displayed the lowest threshold to sounds between 8-16 kHz, indicating best hearing across those frequencies. We found significant differences in auditory thresholds of the ABRs between the sexes, with females showing lower frequency hearing compared to males. However, no significant differences were detected in monaural and binaural ABR amplitudes and latencies between the sexes. We also found no significant differences in craniofacial and pinna dimensions between the sexes. These findings shed novel insights into the auditory systems across species and highlighted for the first time sex differences in auditory thresholds for this rodent species.

Tinnitus has been identified as a potential contributor to anxiety. Thalamo-cortical pathway plays a crucial role in the transmission of auditory and emotional information, but its casual link to tinnitus-associated anxiety remains unclear. In this study, we explore the neural activities in the thalamus and cortex of the sodium salicylate (NaSal)-treated mice, which exhibit both hyperacusis and anxiety-like behaviors. We find an increase in gamma band oscillations (GBO) in both auditory cortex (AC) and prefrontal cortex (PFC), as well as phase-locking between cortical GBO and thalamic neural activity. These changes are attributable to a suppression of GABAergic neuron activity in thalamic reticular nucleus (TRN), and optogenetic activation of TRN reduces NaSal-induced hyperacusis and anxiety-like behaviors. The elevation of endocannabinoid (eCB)/ cannabinoid receptor 1 (CB1R) transmission in TRN contributes to the NaSal-induced abnormalities. Our results highlight the regulative role of TRN in the auditory and limbic thalamic-cortical pathways.

Neural circuits in the auditory brainstem compute interaural time and intensity differences used to determine the locations of sound sources. These circuits display features that are specialized for these functions. The projection from the ventral cochlear nucleus (VCN) to the medial nucleus of the trapezoid (MNTB) body travels along highly myelinated fibers and terminates in the calyx of Held. This monoinnervating synapse emerges during development as multiple inputs are eliminated. We previously demonstrated that elimination of microglia with a colony stimulating factor-1 inhibitor results in impaired synaptic pruning so that multiple calyceal terminals reside on principal cells of MNTB. This inhibitor also resulted in impaired auditory brainstem responses (ABRs), with elevated thresholds and increased peak latencies. Loss of the microglial fractalkine receptor, CX3CR1, decreased peak latencies in the ABR. The mechanisms underlying these effects are not known. One prominent microglial signaling pathway involved in synaptic pruning and plasticity during development and aging is the C1q-initiated compliment cascade. Here we investigated the classical complement pathway initiator, C1q, in auditory brainstem maturation. We found that C1q expression is detected in the MNTB by the first postnatal week. C1q levels increased with age and were detected within microglia and surrounding the soma of MNTB principal neurons. Loss of C1q did not affect microglia-dependent calyceal pruning. Excitatory and inhibitory synaptic markers in the MNTB and LSO were not altered with C1q deletion. ABRs showed that C1q KO mice had normal hearing thresholds but shortened peak latencies. Altogether this study uncovers the developmental time frame of C1q expression in the sound localization pathway and shows a subtle functional consequence of C1q knockdown.

This study aimed to investigate the effects of the intravenous administration of lidocaine in the auditory cortex after the systemic administration of salicylate. Healthy male albino Hartley guinea pigs were divided into two groups. The control group received only lidocaine, whereas the experimental group received lidocaine after checking for the effects of salicylate. Extracellular recordings of spikes in the primary auditory cortex and dorsocaudal areas in healthy albino Hartley guinea pigs were continuously documented (pre- and post-lidocaine, pre- and post-salicylate, and post-salicylate after adding lidocaine to post-salicylate). We recorded 160 single units in the primary auditory cortex from five guinea pigs and 155 single units in the dorsocaudal area from another five guinea pigs to confirm the effects of lidocaine on untreated animals. No significant change was detected in either the threshold or Q 10dB value after lidocaine administration in the primary auditory cortex and dorsocaudal areas. Spontaneous firing activity significantly decreased after lidocaine administration in the primary auditory cortex and dorsocaudal areas. Next, we recorded 160 single units in the primary auditory cortex from five guinea pigs and 137 single units in the dorsocaudal area from another five guinea pigs to determine the effects of lidocaine on salicylate-treated animals. The threshold was significantly elevated after salicylate administration; however, no additional change was detected after adding lidocaine to the primary auditory cortex and dorsocaudal areas. Regarding the Q 10dB value, lidocaine negated the significant changes induced by salicylate in the primary auditory cortex and dorsocaudal areas. Moreover, lidocaine negated the significant changes in spontaneous firing activities induced by salicylate in the primary auditory cortex and dorsocaudal areas. In conclusion, changes in the Q 10dB value and spontaneous firing activities induced by salicylate administration are abolished by lidocaine administration, suggesting that these changes are related to the presence of tinnitus.

JOURNAL/nrgr/04.03/01300535-202510000-00031/figure1/v/2026-04-25T153616Z/r/image-tiff Aminoglycosides are a widely used class of antibacterials renowned for their effectiveness and broad antimicrobial spectrum. However, their use leads to irreversible hearing damage by causing apoptosis of hair cells as their direct target. In addition, the hearing damage caused by aminoglycosides involves damage of spiral ganglion neurons upon exposure. To investigate the mechanisms underlying spiral ganglion neuron degeneration induced by aminoglycosides, we used a C57BL/6J mouse model treated with kanamycin. We found that the mice exhibited auditory deficits following the acute loss of outer hair cells. Spiral ganglion neurons displayed hallmarks of pyroptosis and exhibited progressive degeneration over time. Transcriptomic profiling of these neurons showed significant upregulation of genes associated with inflammation and immune response, particularly those related to the NLRP3 inflammasome. Activation of the canonical pyroptotic pathway in spiral ganglion neurons was observed, accompanied by infiltration of macrophages and the release of proinflammatory cytokines. Pharmacological intervention targeting NLRP3 using Mcc950 and genetic intervention using NLRP3 knockout ameliorated spiral ganglion neuron degeneration in the injury model. These findings suggest that NLRP3 inflammasome–mediated pyroptosis plays a role in aminoglycoside-induced spiral ganglion neuron degeneration. Inhibition of this pathway may offer a potential therapeutic strategy for treating sensorineural hearing loss by reducing spiral ganglion neuron degeneration.

Adaptive myelination is the emerging concept of tuning axonal conduction velocity to the activity within specific neural circuits over time. Sound processing circuits exhibit structural and functional specifications to process signals with microsecond precision: a time scale that is amenable to adjustment in length and thickness of myelin. Increasing activity of auditory axons by introducing sound-evoked responses during postnatal development enhances myelin thickness, while sensory deprivation prevents such radial growth during development. When deprivation occurs during adulthood, myelin thickness was reduced. However, it is unclear whether sensory stimulation adjusts myelination in a global fashion (whole fiber bundles) or whether such adaptation occurs at the level of individual fibers. Using temporary monaural deprivation in mice provided an internal control for a) differentially tracing structural changes in active and deprived fibers and b) for monitoring neural activity in response to acoustic stimulation of the control and the deprived ear within the same animal. The data show that sound-evoked activity increased the number of myelin layers around individual active axons, even when located in mixed bundles of active and deprived fibers. Thicker myelination correlated with faster axonal conduction velocity and caused shorter auditory brainstem response wave VI-I delays, providing a physiologically relevant readout. The lack of global compensation emphasizes the importance of balanced sensory experience in both ears throughout the lifespan of an individual.