Publications using TDT

Recent studies suggest some hippocampal (HC) neurons respond to passively presented sounds in naive subjects, but the specificity and prevalence of these responses remain unclear. We used Neuropixels probes to record unit activity across layers in mid-ventral HC and auditory cortex (ACtx) of awake, untrained mice (male and female) while presenting diverse sounds at typical environmental levels (65–70 dB SPL). A subset of HC neurons exhibited reliable, short latency responses to passive sounds, including tones and broadband noise. HC units showed evidence of tuning for tone frequency but not spectrotemporal features in continuous dynamic moving ripples. Across sound types, HC responses overwhelmingly occurred at stimulus onset; they quickly adapted to continuous sounds and did not respond at sound offset. Among all sounds tested, broadband noise was most effective at driving HC activity. Spectral manipulations indicated response prevalence scaled with increasing spectral bandwidth and density. Similar responses were also observed for visual flash and contrast-modulated noise movies, although these were less common than for broadband noise. Sound-evoked face movements, quantified by total face motion energy (FME), correlated with population-level HC activity. However, many individual units responded regardless of FME strength, suggesting both auditory and motor-correlated inputs. Together, our results show that abrupt sound onsets are sufficient to activate many HC neurons in the absence of learning or behavioral engagement. This supports a role for HC in detecting salient environmental changes and supports the idea that auditory inputs contribute directly to HC function.

The cochlear implant is a widely available hearing restoration technology that can provide speech understanding in quiet environments. This technology struggles however, in noisy settings or situations involving multiple speakers. The primary cause of these performance limitations is a poor neural interface, in which the bony wall of the cochlea separates the electrode surface from the auditory nerve fibers, thus causing unwanted current spread and non-specific frequency activation. This study utilizes an alternative auditory prosthetic technology (auditory nerve implant, ANI) that enables direct auditory nerve stimulation, which provides a potentially superior neural interface and enables more precise targeting of auditory nerve fibers than traditional cochlear implants. As auditory nerve implants progress towards clinical translation, new implant designs and stimulation strategies will be created. Animal models to efficiently test and iterate through these new designs will be useful for the continued development of ANI technology. We present a viable surgical approach in the non-human primate (rhesus macaque) along with electrophysiological results that demonstrate robust activation of the auditory system at low current levels via intraneural stimulation. Our findings indicate that the rhesus macaque, which possesses an inner ear anatomy more similar to the human compared to other animal models used in the hearing field (e.g., rodents, felines and ferrets), has strong potential as a useful preclinical testbed involving an upright head model for future ANI prototypes and stimulation strategy development.

Stories, Chirps, And Noisy Sentences (MEG-SCANS) is a dataset that provides raw magnetoencephalography (MEG) recordings from 24 German-speaking subjects. Each subject listened to approximately one hour of stimuli, including two audiobooks, sentences from the Oldenburger Matrix Sentence Test (OLSA) for Speech Reception Threshold (SRT) assessment, and short up-chirps used to assess MEG signal quality. The dataset includes MEG data, structural MRI (Magnetic Resonance Imaging) scans of the head, corresponding audio material (audiobooks, OLSA envelopes, and chirp stimuli), and behavioral audiogram and SRT results from hearing screenings. Organized according to the Brain Imaging Data Structure (BIDS), this resource offers a robust benchmark for large-scale encoding/decoding analyses of temporally-resolved brain responses to speech. Comprehensive Matlab and Python code are included to replicate key data validations, ensuring transparency and reproducibility.

The ability to associate environmental stimuli with positive outcomes is a fundamental form of learning. While extensive research has focused on midbrain dopamine neurons during associative learning, less is known about learning-mediated changes in the afferents that shape dopamine neuron responses. We demonstrate in rats that during critical phases of learning, anion homeostasis in midbrain inhibitory GABA neurons - a primary source of input to dopamine neurons - is disrupted due to downregulation of the potassium chloride cotransporter KCC2. This alteration in GABA neurons preferentially impacted lateral mesoaccumbal dopamine pathways and was not observed after learning was established. At the network level, learning-mediated KCC2 downregulation was associated with enhanced synchronization between individual GABA neurons and increased dopamine responses to rewards and reward-related stimuli. Conversely, enhancing KCC2 function during learning reduced GABA synchronization, diminished relevant dopamine signaling, and prevented cue-reward associations. Thus, circuit-specific adaptations in midbrain GABA neurons are crucial for forming new reward-related behaviors.

No pharmacological interventions exist that can restore or preserve auditory function in the mammalian cochlea. Auditory hair cells (HCs) do not spontaneously regenerate, leading to permanent hearing loss. In non-mammalian vertebrates, HC regeneration happens through proliferation and differentiation of their clonally related supporting cells (SCs). The present study supports the potential of quinoxaline (Qx), a nonsteroidal anti-inflammatory compound, to stimulate SC proliferation in the auditory sensory epithelium, a process that may prime the tissue for future HC regeneration. We synthesized a series of Qx derivatives by introducing various substitutions, ranging from hydrophilic to lipophilic. Seventy analogs were generated and tested in vitro and in vivo. Among those, only one (Qx-100) exhibited the best medicinal chemistry profile and was further modified to expand the structure–activity relationship of the chemotype, develop additional analogs, and optimize potency, bioavailability, and in vivo efficacy. Ten new lead variants were generated. Of those, Qx-294 and Qx-301 demonstrated promising in vitro Absorption, Distribution, Metabolism, and Excretion (ADME) profiles and were selected for further testing. Overall, both compounds were rapidly absorbed in zebrafish and mice and promoted cell proliferation in vitro and in vivo without signs of apoptosis, supporting their potential for sensory HC regeneration.

The CCKBR agonists induce neocortical long-term potentiation of excitatory synaptic transmission and enhance memory formation, while its antagonists weaken the potentiation in the amygdala and alleviate depression-like behaviors. However, the mechanism that drives CCKBR dependent long-term potentiation remains elusive. There is also no signaling pathway-biased CCKBR agonist to modulate the potentiation. Here, we discover a β-arrestin biased CCKBR agonist MF-8 with IC50 = 0.9 nM. The activation of CCKBR with MF-8 fails to induce the potentiation but efficiently induces CCKBR endocytosis. Multi-Electrode Array results demonstrate that the potentiation is dependent on Gαq/11-Ca2+ and Gαs-cAMP signaling pathways. The potentiation is entirely blocked by MF-8 through β-arrestin signaling. Furthermore, MF-8 effectively inhibits the formation of cue-to-cue associative fear memory. These results reveal the signal pathway preference of the CCKBR long-term potentiation and identify a blocker of the potentiation, which provides us with broader insights into developing drugs targeting CCKBR.

Drugs of abuse in adolescence impact brain maturation and increase psychiatric risk, with differences in sensitivity between males and females. Amphetamine in early adolescence (postnatal day; PND 21 ± 1–32 ± 1) in male, but not female mice, causes dopamine axons intended to innervate the nucleus accumbens and to grow ectopically to the prefrontal cortex (PFC). This is mediated by drug-induced downregulation of the Netrin-1 receptor DCC. How off-target dopamine axons function in the adult PFC remains to be determined. Here we report that males and females show place preference for amphetamine in early adolescence. However, only in males, amphetamine increases PFC dopamine transporter expression in adulthood (PND 101 ± 15): leading to aberrant baseline dopamine transients, faster dopamine release, and exaggerated responses to acute methylphenidate. Upregulation of DCC in adolescence, using CRISPRa, prevents all these changes. Mesolimbic dopamine axons rerouted to the PFC in adolescence retain anatomical and functional phenotypes of their intended target, rendering males enduringly vulnerable to the harmful effects of drugs of abuse.

The gene therapy achieved by AAV-mediated otoferlin-overexpression is an effective therapeutic strategy for congenital deafness. However, achieving its physiological and endogenous patterns of expression remains challenging. Here, we generate the homologous mutation Otof c.1315 C > T (p.R439*), equivalent to OTOF c.1273 C > T (p.R425*) found in humans with profound deafness, to create a nonsense mutation-induced deaf mouse model. We then deliver the ‘RESTART v3’ system, which is a CRISPR-free RNA base editor for nonsense mutation suppression, into the cochlea of the mice. We achieve physiological otoferlin expression, and the edited premature termination codon is reverse-mutated to the original amino acid. We observe significant hearing restoration and enhancement of the behavioral auditory startle reflex. Thus, our study presents a successful RNA editing strategy to significantly restore hereditary deafness in mice carrying the specific Otof nonsense mutation, which holds great promise for future clinical translation.

The hypothalamus is critical for regulating behaviors essential for survival and locomotion, but how it integrates internal needs and transmits locomotion commands to the spinal cord (SC) remains unclear. We found that glutamatergic neurons in lateral hypothalamic area (LHA) are essential for regulating motivated locomotor activity. Using single-neuron projectome analysis, trans-synaptic tracing, and optogenetic manipulation, we showed that LHA facilitates motivated locomotion during food seeking via pontine reticular nucleus, oral part (PnO) projection neurons, rather than direct SC projections or indirect stress signaling via medial septum and diagonal band. Activating PnO-SC projection neurons also initiated locomotion. Importantly, LHA-PnO projection neurons were crucial for regulating locomotor recovery following mouse spinal cord injury (SCI). Motor cortex signals gated LHA deep brain stimulation treatment markedly promoted long-term restoration of hindlimb motor functions after severe SCI. Thus, we have identified a hypothalamic-pontine-spinal pathway and the stimulation paradigm for potential therapeutic intervention after SCI.

Ciliogenesis requires an orchestrated interaction between the Golgi apparatus and centrioles via vesicle trafficking, yet this process is still poorly understood. Phosphatidylinositol 4-kinase β (PI4KB) is a conserved kinase that localizes to the Golgi for generating phosphatidylinositol 4-phosphate, an important lipid component related to cilium formation. Here, we demonstrate a previously uncharacterized mechanism of PI4KB in regulating Rab11a to enable proper ciliogenesis. PI4KB kinase activity maintains the normal vesicle density around the Golgi and Rab11a localization to centrioles in ciliogenesis. Inhibition of PI4KB activity leads to the reduced centriole localization but accumulation of Rab11a on the Golgi. We identified that the activation of Rab11a relies on PI4KB activity, while inactive Rab11a–guanosine diphosphate stably associates with Golgi and fails to undergo outward delivery. Autosomal-dominant nonsyndromic sensorineural hearing loss mutations in PI4KB abnormally intensify PI4KB interaction with Rab11a, leading to the aberrant subcellular Rab11a localization and defective ciliogenesis. Collectively, our study delineates a critical role for PI4KB in post–Golgi vesicle formation and ciliogenesis.

Memory consolidation enables animals to draw on past experiences to guide future behavior. This process involves system- and synaptic-level changes and predominantly occurs during sleep. While hippocampal-cortical circuits are well studied in this context, the contributions of other systems, including dopaminergic circuits—key players in learning-related processes—remain poorly understood. Ventral tegmental area dopaminergic (VTA DA ) neurons are active during sleep and suggested to participate in memory consolidation processes; however, causal evidence for this is lacking. Using calcium-dependent fiber photometry, electrophysiology, and chemogenetic and optogenetic manipulations across learning paradigms, we explore the functions of VTA DA neuronal activity during sleep. We show that VTA DA activity during nonrapid eye movement sleep is experience dependent, is enhanced by motor skill and associative learning, facilitates motor skill memory consolidation, and exhibits a motor learning–dependent increase in temporal coordination with cortical spindle oscillations. Our findings uncover a previously unidentified function for VTA DA neurons in consolidating memories during sleep, advancing understanding of this central neuromodulator’s functions in regulating fundamental biological processes.

As the Arctic warms and becomes more accessible to human activities and associated noise sources, it is important to understand the auditory capabilities of ice-associated marine mammals that rely on sound. In this study, the in-air hearing of one adult bearded seal ( Erignathus barbatus ) was measured in ambient outdoor conditions using psychophysical methods. 50% detection thresholds were measured for 10 frequencies (0.04–51.2 kHz) that extend across the subject’s hearing range. For low to mid frequencies (0.04–12.8 kHz), thresholds were constrained, or masked, by ambient noise. Thresholds obtained at higher frequencies (25.6–51.2 kHz) were sufficiently elevated above background noise to provide absolute measures of hearing sensitivity. These measurements reveal that the high-frequency roll-off for bearded seals is in alignment with available auditory data for related species despite more than 11 million years of evolutionary isolation. Further, the data collected at low and mid frequencies enable an unconventional estimation of critical ratios, which can be applied in masking models. Collectively, these findings for bearded seals listening for airborne sounds highlight auditory similarities within the northern clade of phocid Carnivores and improve predictions of potential noise effects for seals in changing Arctic soundscapes.

Objective: To investigate the delivery efficiency of human umbilical cord mesenchymal stem cell-derived exosomes (hucMSC-EXOs) via intratympanic injection into vestibular end organs, evaluate their protective effects against gentamicin-induced vestibular dysfunction and hearing loss on gentamicin-induced vestibular dysfunction and hearing loss, and explore their regulatory mechanisms on hair cell apoptosis and autophagy. Methods: Exosome characteristics were identified by transmission electron microscopy, nanoparticle tracking analysis, and Western blot. PKH26 labeling was used to trace their distribution in the vestibule. SD rats were randomly divided into four groups: control group, gentamicin group (GEN group), gentamicin + exosome group (GEN + EXO group), and gentamicin + dexamethasone group (GEN + DEX group). On day 6 after administration, vestibular function was assessed via open-field test and beam balance test. On day 7, high-frequency hearing (32 kHz) was detected by auditory brainstem response (ABR). The quantity and structural changes of hair cells were analyzed by immunofluorescence staining and scanning electron microscopy. Proteomics was used to analyze differentially expressed proteins in vestibular tissues treated with dexamethasone or hucMSC-EXOs. The regulatory effects on Caspase-3 (apoptosis) and LC3 (autophagy) were validated by immunofluorescence. Results: hucMSC-EXOs administered via intratympanic injection were found to target the utricle, saccule, and crista ampullaris. Behavioral studies showed that the GEN + EXO group exhibited significant suppression of gentamicin-induced reduction in total movement distance (p < 0.05) and movement speed (p < 0.05, superior to the GEN + DEX group), with a 60.5% reduction in beam balance test passage time (p < 0.05). ABR results revealed that the auditory threshold at 32 kHz in the GEN + EXO group was 18.3 dB SPL lower than that in the injury group (p < 0.01), with no statistical difference compared to the GEN + DEX group. Hair cell counting showed significant protective effects of exosomes in reducing hair cell loss in the utricular striola (+ 25%), saccular striola (+ 44%), and central crista ampullaris (+ 44%), with partial regions outperforming the GEN + DEX group (e.g., 109% repair rate in the saccular striola). Scanning electron microscopy confirmed that exosomes reduced hair cell cilia loss and structural vacuolization. Proteomics showed significant activation of the complement and coagulation cascades in the GEN group, while the GEN + EXO group enhanced autophagy via enriching the vesicle transport-related SNARE interaction pathway and improved energy metabolism and oxidative stress by regulating metabolic pathways. Immunofluorescence demonstrated that exosomes significantly reduced the expression of the apoptosis marker Caspase-3 (p < 0.01) and enhanced the activity of the autophagy marker LC3 (p < 0.05). Conclusions: hucMSC-EXOs delivered via intratympanic injection effectively target vestibular sensory epithelia, significantly suppressing gentamicin-induced balance dysfunction and high-frequency hearing loss, with superior efficacy in partial indicators (e.g., movement speed, saccular hair cell repair) compared to dexamethasone. hucMSC-EXOs exert protective effects through a dual mechanism of "anti-apoptosis and pro-autophagy," providing a novel therapeutic strategy for vestibular hair cell injury.

The insula is critical for integrating sensory information from the body with that arising from the environment. Although previous studies suggested that posterior insula is sensitive to sounds, these studies usually involved behaviorally relevant stimuli. Further, auditory response properties of the human insula have not previously been studied on the single neuron level. Here, we provide the first report of a population of human single neuron data from both anterior and posterior insula and provide comparative data from the primary auditory cortex, recorded intracranially from human participants during passive listening. In each condition, more than 340 single neurons were recorded in 12 participants of either sex. Almost a third of neurons in posterior insula and a smaller subset in anterior insula responded to simple tones and clicks. Responsive neurons were distributed throughout posterior and anterior insula and showed preferred frequency tuning. Onset latencies in insula were short, but response durations were significantly shorter than primary auditory cortex. Overall, these data show that insula neurons respond to auditory stimuli even in nonbehaviorally relevant contexts and change our understanding of this brain region, suggesting that processing basic auditory stimuli is an important integrative function of insular cortex.

Brain-wide communication supporting flexible behavior requires coordination between sensory and associative regions but how brain networks route sensory information at fast timescales to guide action remains unclear. Using human intracranial electrophysiology and spiking neural networks during spatial attention tasks, where participants detected targets at cued locations, we show that high-frequency activity bursts (HFAbs) mark temporal windows of elevated population firing that enable fast, long-range communications. HFAbs were evoked by sensory cues and targets, dynamically coupled to low-frequency rhythms. Notably, both the strength of cue-evoked HFAbs and their decoupling from slow rhythms predicted behavioral accuracy. HFAbs synchronized across the brain, revealing distinct cue- and target-activated subnetworks. These subnetworks exhibited lead-lag dynamics following target onset, with cue-activated subnetworks preceding target-activated subnetworks when cues were informative. Computational modeling suggested that HFAbs reflect transitions to population spiking, denoting temporal windows for network communications supporting attentional performance. These findings establish HFAbs as signatures of population state transitions, supporting information routing across distributed brain networks.

Sensorineural hearing loss (SNHL) caused by human cytomegalovirus (HCMV) infection involves alterations in both the central auditory pathways and cochlear structures. Immediate early (IE) proteins are critical for HCMV pathogenicity and have been associated with neurodevelopmental disorders; however, their contribution to HCMV-associated SNHL remains unclear. Here, we generated transgenic mouse models expressing HCMV IE1 and IE2 protein to investigate their effects on auditory function and cochlear pathology. Auditory brainstem response (ABR) measurements revealed that expression of IE2, but not IE1, led to significantly elevated ABR thresholds and impaired auditory processing. IE2-transgenic mice exhibited synaptic loss, hair cell degeneration, and neuronal atrophy in auditory regions. scRNA-seq analysis indicated broad activation of inflammatory pathways and cytokines within the cochlea, along with disruptions in mitochondrial and metabolic pathways, suggesting that IE2 may contribute to hearing loss through mitochondrial impairment and inflammation. Transmission electron microscopy of cochlear tissues showed severe morphological abnormalities and a marked reduction in mitochondrial number in spiral ganglion neurons (SGNs). Further mechanistic investigation demonstrated that IE2 interacts with TSC2, leading to hyperactivation of mTOR signaling, metabolic dysregulation, and mitochondrial dysfunction. Importantly, administration of mTOR inhibitors substantially alleviated IE2-induced auditory deficits, hair cell degeneration, and neuronal atrophy. These findings identify IE2 through TSC2-mTOR-mediated mitochondrial dysfunction, metabolic reprogramming, and neuroinflammation leading to SNHL. Our study reveals a previously unrecognized mechanism linking IE2 protein expression to auditory neurodegeneration and suggests mTOR modulation as a potential therapeutic strategy for congenital HCMV infection and associated hearing loss.

Damage to inner hair cells (IHCs) is a leading cause of hearing loss, typically initiating at the base region of the basilar membrane. However, the mechanisms and preventative strategies for IHC damage remain to be elucidated. This study revealed that IHCs in the low-frequency region exhibit a significantly faster calcium clearance rate than high-frequency IHCs. This difference is associated with different PMCA1 expression. We then generated an IHC-specific Pmca1 knockout mouse model ( Pmca1 CKO) exhibiting profound hearing loss and IHC death. Using single-cell RNA-seq analysis, we found that the differentially expressed genes (DEGs) were related to tetrahydrofolate biosynthesis, DNA damage, and DNA repair dysfunction. We therefore treated Pmca1 CKO mice with folic acid and found that it protected IHCs by reducing γ-H2A.X levels. In addition, we found that folic acid protected IHCs from noise-induced damage. Overall, our findings suggest that disrupted calcium homeostasis plays a role in IHC damage and that folic acid may be a promising therapeutic agent for protecting hair cells.

Spatial disorientation is emerging as an early cognitive biomarker of dementia, but the underlying neural mechanisms remain undefined. The anterodorsal nucleus of the thalamus (ADn) exhibits early and selective vulnerability to pathological misfolded forms of tau, a major hallmark of Alzheimer's disease. As the ADn contains a high density of head direction (HD) cells, we hypothesized that ptau disrupts HD cell activity, promoting spatial disorientation. To test this, we virally expressed human mutant tau in the ADn of adult wild-type and C1ql2-Cre mice. ADn-tau mice were defined by phosphorylated and oligomeric forms of tau in ADn somata and axon terminals. During initial spatial learning, ADn-tau mice exhibited increased looping behavior, indicative of spatial disorientation. Using in vivo extracellular recordings, we found that ADn cells had reduced directionality, lower directional coherence, and altered burst firing. These findings suggest that early alterations in HD signaling are predictive of future cognitive decline.

Animals routinely make self-motivated choices about whether to initiate interactions with same- or opposite-sex partners. However, it remains unclear whether these choices are motivated by drive states that exhibit signatures of moment-to-moment social satiety. To test this, we designed a fully automated two-choice social operant paradigm where mice can choose between same- and opposite-sex social rewards that are delivered for interaction with systematically varying durations. We find that although both males and females have stable choice biases, only males exhibit behavioral signatures of moment-to-moment social satiety. Using a simple normative model to capture patterns of social choice, we observe that behavior is better fit by a model with a single social drive and choice bias, rather than a model with independent drives for same- and opposite-sex interactions. Together, our data reveal behavioral signatures of social satiety and offer insights into the underlying homeostatic and motivational drives that govern social choices.

Age-related hearing loss (ARHL) represents a progressive auditory disorder. Growing evidence indicates that degradation of connexin 26 (Cx26) in cochlear may constitute one of the pathogenic mechanisms in ARHL. However, the molecular mechanisms underlying age-related Cx26 degradation remain unclear. We systematically analyzed Cx26 expression patterns in C57BL/6J mice across different age groups and confirmed an age-dependent downregulation of Cx26 in the mouse cochlea. Notably, we observed concurrent upregulation of endoplasmic reticulum (ER) stress markers Glucose-regulated protein 78 (GRP78) and protein disulfide isomerase (PDI) in aged cochlear tissues. Furthermore, in vitro experiments demonstrated that ER stress significantly reduced Cx26 protein levels in cochlear explants. Mechanistically, we observed enhanced expression of ubiquitination-related proteins Nedd4 and Eps15 with evident colocalization with Cx26 in an ER stress mouse model. In summary, our findings demonstrate that Cx26 ubiquitination mediated by cochlear ER stress is the main cause of Cx26 degradation in the cochlea of aged mice.