Publications using TDT

Aminoglycoside ototoxicity is common in clinical practice but reliable protective agents currently do not exist. Aminoglycoside regimens causing ototoxicity in different laboratory animals are under investigation. The assessment method used most commonly to determine auditory effects is the auditory brainstem response (ABR). Distortion product otoacoustic emissions (DPOAE) have been used less frequently. A precise recommendation on the specific method to assess peripheral auditory function before and after aminoglycoside toxicity in mice does not exist. In order to evaluate various mouse models for ototoxic injury caused by various aminoglycoside regimens, there is a need for performing preliminary tests in small cohorts before large experiments. The aim of our study was to investigate different aminoglycoside regimens that cause substantial ototoxic damage in vivo. Aminoglycosides are safe and produce a detectable hearing threshold shift in a small cohort of mice that can be used as a model for preliminary tests. Different ototoxic regimens were assessed by ABR and DPOAE measurements pre- and post-treatment. Further, the sensory cell loss was quantified by counting hair cells in the cochlea. It was revealed that an ototoxic regimen with kanamycin twice daily for 15 consecutive days is safe, well tolerated and produces an early significant hearing threshold shift detected by DPOAE in a small cohort of mice. The study compared ABR and DPOAE in mentioned regimens for the first time and illustrated that DPOAE is well suited for detecting hearing threshold shifts in high frequencies before ABR threshold shifts occur in accordance with predominating outer hair cell damage mainly in the basal turn of the cochlea.

Hearing loss is a major risk factor for tinnitus, hyperacusis, and central auditory processing disorder. Although recent studies indicate that hearing loss causes neuroinflammation in the auditory pathway, the mechanisms underlying hearing loss-related pathologies are still poorly understood. We examined neuroinflammation in the auditory cortex following noise-induced hearing loss (NIHL) and its role in tinnitus in rodent models. Our results indicate that NIHL is associated with elevated expression of proinflammatory cytokines and microglial activation-two defining features of neuroinflammatory responses-in the primary auditory cortex (AI). Genetic knockout of tumor necrosis factor alpha (TNF-α) or pharmacologically blocking TNF-α expression prevented neuroinflammation and ameliorated the behavioral phenotype associated with tinnitus in mice with NIHL. Conversely, infusion of TNF-α into AI resulted in behavioral signs of tinnitus in both wild-type and TNF-α knockout mice with normal hearing. Pharmacological depletion of microglia also prevented tinnitus in mice with NIHL. At the synaptic level, the frequency of miniature excitatory synaptic currents (mEPSCs) increased and that of miniature inhibitory synaptic currents (mIPSCs) decreased in AI pyramidal neurons in animals with NIHL. This excitatory-to-inhibitory synaptic imbalance was completely prevented by pharmacological blockade of TNF-α expression. These results implicate neuroinflammation as a therapeutic target for treating tinnitus and other hearing loss-related disorders.

Objective: The adenosinergic system may influence excitability in the brain. Endogenous and exogenous adenosine has anticonvulsant activity presumably by activating A1 receptors. Adenosine A1 receptor agonist 2-chloro-N6-cyclopentyladenosine (CCPA) may thus bolster anticonvulsant effects, but its action and the number of A1 receptors at different developmental stages are not known. Methods: Hippocampal epileptic afterdischarges (ADs) were elicited in 12-, 15-, 18-, 25-, 45-, and 60-day-old rats. Stimulation and recording electrodes were implanted into the dorsal hippocampus. The A1 receptor agonist 2-chloro-N6-cyclopentyladenosine (CCPA, 0.5 or 1 mg/kg) was administered intraperitoneally 10 min before the first stimulation. Control animals were injected with saline. All rats were stimulated with a 2-s series of 1-ms biphasic pulses delivered at 60 Hz with increasing stepwise intensity (0.05-0.6 mA). Each age and dose group contained 9-14 animals. The AD thresholds and durations were evaluated, and the A1 receptors were detected in the hippocampus in 7-, 10-, 12-, 15-, 18-, 21-, 25-, 32-, and 52-day-old rats. Results: Both CCPA doses significantly increased hippocampal AD thresholds in 12-, 15-, 18-, and 60-day-old rats compared to controls. In contrast, the higher dose significantly decreased AD threshold in the 25-day-old rats. The AD durations were significantly shortened in all age groups except for 25-day-old rats where they were significantly prolonged. A1 receptor expression in the hippocampus was highest in 10-day-old rats and subsequently decreased. Significance: The adenosine A1 receptor agonist CCPA exhibited anticonvulsant activity at all developmental stages studied here except for 25-day-old rats. Age-related differences might be due to the development of presynaptic A1 receptors in the hippocampus.

This study combined a previously developed optical system with two additional key elements: a supercontinuum light source characterized by high output power and an analytical technique that effectively extracts interference signals required for improving the detection limit of vibration amplitude. Our system visualized 3D tomographic images and nanometer scale vibrations in the cochlear sensory epithelium of a live guinea pig. The transverse- and axial-depth resolution was 3.6 and 2.7 µm, respectively. After exposure to acoustic stimuli of 21-25 kHz at a sound pressure level of 70-85 dB, spatial amplitude and phase distributions were quantified on a targeted surface, whose area was 522 × 522 μm2.

Noise trauma causes loss of synaptic connections between cochlear inner hair cells (IHCs) and the spiral ganglion neurons (SGNs). Such synaptic loss can trigger slow and progressive degeneration of SGNs. Macrophage fractalkine signaling is critical for neuron survival in the injured cochlea, but its role in cochlear synaptopathy is unknown. Fractalkine, a chemokine, is constitutively expressed by SGNs and signals via its receptor CX3CR1 that is expressed on macrophages. The present study characterized the immune response and examined the function of fractalkine signaling in degeneration and repair of cochlear synapses following noise trauma. Adult mice wild type, heterozygous and knockout for CX3CR1 on a C57BL/6 background were exposed for 2 h to an octave band noise at 90 dB SPL. Noise exposure caused temporary shifts in hearing thresholds without any evident loss of hair cells in CX3CR1 heterozygous mice that have intact fractalkine signaling. Enhanced macrophage migration toward the IHC-synaptic region was observed immediately after exposure in all genotypes. Synaptic immunolabeling revealed a rapid loss of ribbon synapses throughout the basal turn of the cochlea of all genotypes. The damaged synapses spontaneously recovered in mice with intact CX3CR1. However, CX3CR1 knockout (KO) animals displayed enhanced synaptic degeneration that correlated with attenuated suprathreshold neural responses at higher frequencies. Exposed CX3CR1 KO mice also exhibited increased loss of IHCs and SGN cell bodies compared to exposed heterozygous mice. These results indicate that macrophages can promote repair of damaged synapses after moderate noise trauma and that repair requires fractalkine signaling.

A key challenge in neuroscience is understanding how sensory stimuli give rise to perception, especially when the process is supported by neural activity from an extended network of brain areas. Perception is inherently subjective, so interrogating its neural signatures requires, ideally, a combination of three factors: (1) behavioral tasks that separate stimulus-driven activity from perception per se; (2) human subjects who self-report their percepts while performing those tasks; and (3) concurrent neural recordings acquired at high spatial and temporal resolution. In this study, we analyzed human electrocorticographic recordings obtained during an auditory task which supported mutually exclusive perceptual interpretations. Eight neurosurgical patients (5 male; 3 female) listened to sequences of repeated triplets where tones were separated in frequency by several semitones. Subjects reported spontaneous alternations between two auditory perceptual states, 1-stream and 2-stream, by pressing a button. We compared averaged auditory evoked potentials (AEPs) associated with 1-stream and 2-stream percepts and identified significant differences between them in primary and nonprimary auditory cortex, surrounding auditory-related temporoparietal cortex, and frontal areas. We developed classifiers to identify spatial maps of percept-related differences in the AEP, corroborating findings from statistical analysis. We used one-dimensional embedding spaces to perform the group-level analysis. Our data illustrate exemplar high temporal resolution AEP waveforms in auditory core region; explain inconsistencies in perceptual effects within auditory cortex, reported across noninvasive studies of streaming of triplets; show percept-related changes in frontoparietal areas previously highlighted by studies that focused on perceptual transitions; and demonstrate that auditory cortex encodes maintenance of percepts and switches between them.SIGNIFICANCE STATEMENT The human brain has the remarkable ability to discern complex and ambiguous stimuli from the external world by parsing mixed inputs into interpretable segments. However, one's perception can deviate from objective reality. But how do perceptual discrepancies occur? What are their anatomical substrates? To address these questions, we performed intracranial recordings in neurosurgical patients as they reported their perception of sounds associated with two mutually exclusive interpretations. We identified signatures of subjective percepts as distinct from sound-driven brain activity in core and non-core auditory cortex and frontoparietal cortex. These findings were compared with previous studies of auditory bistable perception and suggested that perceptual transitions and maintenance of perceptual states were supported by common neural substrates.

Precise neural sequences are associated with the production of well-learned skilled behaviors. Yet, how neural sequences arise in the brain remains unclear. In songbirds, premotor projection neurons in the cortical song nucleus HVC are necessary for producing learned song and exhibit precise sequential activity during singing. Using cell-type specific calcium imaging we identify populations of HVC premotor neurons associated with the beginning and ending of singing-related neural sequences. We characterize neurons that bookend singing-related sequences and neuronal populations that transition from sparse preparatory activity prior to song to precise neural sequences during singing. Recordings from downstream premotor neurons or the respiratory system suggest that pre-song activity may be involved in motor preparation to sing. These findings reveal population mechanisms associated with moving from non-vocal to vocal behavioral states and suggest that precise neural sequences begin and end as part of orchestrated activity across functionally diverse populations of cortical premotor neurons.

Speech communication in real-world environments requires adaptation to changing acoustic conditions. How the human auditory cortex adapts as a new noise source appears in or disappears from the acoustic scene remain unclear. Here, we directly measured neural activity in the auditory cortex of six human subjects as they listened to speech with abruptly changing background noises. We report rapid and selective suppression of acoustic features of noise in the neural responses. This suppression results in enhanced representation and perception of speech acoustic features. The degree of adaptation to different background noises varies across neural sites and is predictable from the tuning properties and speech specificity of the sites. Moreover, adaptation to background noise is unaffected by the attentional focus of the listener. The convergence of these neural and perceptual effects reveals the intrinsic dynamic mechanisms that enable a listener to filter out irrelevant sound sources in a changing acoustic scene.

The extent to which the primary auditory cortex (A1) participates in instructing animal behavior remains debated. Although multiple studies have shown A1 activity to correlate with animals' perceptual judgments (Jaramillo and Zador, 2011; Bizley et al., 2013; Rodgers and DeWeese, 2014), others have found no relationship between A1 responses and reported auditory percepts (Lemus et al., 2009; Dong et al., 2011). To address this ambiguity, we performed chronic recordings of evoked local field potentials (eLFPs) in A1 of head-fixed female rats performing a two-alternative forced-choice auditory discrimination task. Rats were presented with two interleaved sequences of pure tones from opposite sides and had to indicate the side from which the higher-frequency target stimulus was played. Animal performance closely correlated (rrm = 0.68) with the difference between the target and distractor eLFP responses: the more the target response exceeded the distractor response, the better the animals were at identifying the side of the target frequency. Reducing the evoked response of either frequency through stimulus-specific adaptation affected performance in the expected way: target localization accuracy was degraded when the target frequency was adapted and improved when the distractor frequency was adapted. Target frequency eLFPs were stronger on hit trials than on error trials. Our results suggest that the degree to which one stimulus stands out over others within A1 activity may determine its perceptual saliency for the animals and accordingly bias their behavioral choices.SIGNIFICANCE STATEMENT The brain must continuously calibrate the saliency of sensory percepts against their relevance to the current behavioral goal. The inability to ignore irrelevant distractors characterizes a spectrum of human attentional disorders. Meanwhile, the connection between the neural underpinnings of stimulus saliency and sensory decisions remains elusive. Here, we record local field potentials in the primary auditory cortex of rats engaged in auditory discrimination to investigate how the cortical representation of target and distractor stimuli impacts behavior. We find that the amplitude difference between target- and distractor-evoked activity predicts discrimination performance (rrm = 0.68). Specific adaptation of target or distractor shifts performance either below or above chance, respectively. It appears that recent auditory history profoundly influences stimulus saliency, biasing animals toward diametrically-opposed decisions.

The acoustic dimensions that distinguish speech sounds (like the vowel differences in “boot” and “boat”) also differentiate speakers’ voices. Therefore, listeners must normalize across speakers without losing linguistic information. Past behavioral work suggests an important role for auditory contrast enhancement in normalization: preceding context affects listeners’ perception of subsequent speech sounds. Here, using intracranial electrocorticography in humans, we investigate whether and how such context effects arise in auditory cortex. Participants identified speech sounds that were preceded by phrases from two different speakers whose voices differed along the same acoustic dimension as target words (the lowest resonance of the vocal tract). In every participant, target vowels evoke a speaker-dependent neural response that is consistent with the listener’s perception, and which follows from a contrast enhancement model. Auditory cortex processing thus displays a critical feature of normalization, allowing listeners to extract meaningful content from the voices of diverse speakers.

Objective: Spasmodic dysphonia (SD) is a debilitating voice/speech disorder without an effective cure. To obtain a better understanding of the underlying cortical neural mechanism of the disease we analyzed electroencephalographic (EEG) signals of people with SD during voice production. Method: Ten SD individuals and 10 healthy volunteers produced 50 vowel vocalization epochs of 2500 ms duration. Two EEG features were derived: (1) event-related change in spectral power during vocalization relative to rest, (2) inter-regional spectral coherence. Results: During early vocalization (500-1000 ms) the SD group showed significantly larger alpha band spectral power over the left motor cortex. During late vocalization (1000-2500 ms) SD patients showed a significantly larger gamma band coherence between left somatosensory and premotor cortical areas. Conclusions: Two atypical patterns of cortical activity characterize the pathophysiology of spasmodic dysphonia during voice production: (1) a reduced movement-related desynchronization of motor cortical networks, (2) an excessively large synchronization between left somatosensory and premotor cortical areas. Significance: The pathophysiology of SD is characterized by an abnormally high synchronous activity within and across cortical neural networks involved in voice production that is mainly lateralized in the left hemisphere.

Targeting specific cell types in the mammalian inner ear is important for treating genetic hearing loss due to the different cell type-specific functions. Adeno-associated virus (AAV) is an efficient in vivo gene transfer vector, and it has demonstrated promise for treating genetic hearing loss. Although more than 100 AAV serotypes have been identified, few studies have investigated whether AAV can be distributed to specific inner ear cell types. Here we screened three EGFP-AAV reporter constructs (serotypes DJ, DJ8, and PHP.B) in the neonatal mammalian inner ear by injection via the round window membrane to determine the cellular specificity of the AAV vectors. Sensory hair cells, supporting cells, cells in Reissner's membrane, interdental cells, and root cells were successfully transduced. Hair cells in the cochlear sensory epithelial region were the most frequently transduced cell type by all tested AAV serotypes. The recombinant DJ serotype most effectively transduced a range of cell types at a high rate. Our findings provide a basis for improving treatment of hereditary hearing loss using targeted AAV-mediated gene therapy.

Hereditary hearing loss often results from mutation of genes expressed by cochlear hair cells. Gene addition using AAV vectors has shown some efficacy in mouse models, but clinical application requires two additional advances. First, new AAV capsids must mediate efficient transgene expression in both inner and outer hair cells of the cochlea. Second, to have the best chance of clinical translation, these new vectors must also transduce hair cells in non-human primates. Here, we show that an AAV9 capsid variant, PHP.B, produces efficient transgene expression of a GFP reporter in both inner and outer hair cells of neonatal mice. We show also that AAV9-PHP.B mediates almost complete transduction of inner and outer HCs in a non-human primate. In a mouse model of Usher syndrome type 3A deafness (gene CLRN1), we use AAV9-PHP.B encoding Clrn1 to partially rescue hearing. Thus, we have identified a vector with promise for clinical treatment of hereditary hearing disorders, and we demonstrate, for the first time, viral transduction of the inner ear of a primate with an AAV vector.

Maintaining average activity within a set-point range constitutes a fundamental property of central neural circuits. However, whether and how activity set points are regulated remains unknown. Integrating genome-scale metabolic modeling and experimental study of neuronal homeostasis, we identified mitochondrial dihydroorotate dehydrogenase (DHODH) as a regulator of activity set points in hippocampal networks. The DHODH inhibitor teriflunomide stably suppressed mean firing rates via synaptic and intrinsic excitability mechanisms by modulating mitochondrial Ca2+ buffering and spare respiratory capacity. Bi-directional activity perturbations under DHODH blockade triggered firing rate compensation, while stabilizing firing to the lower level, indicating a change in the firing rate set point. In vivo, teriflunomide decreased CA3-CA1 synaptic transmission and CA1 mean firing rate and attenuated susceptibility to seizures, even in the intractable Dravet syndrome epilepsy model. Our results uncover mitochondria as a key regulator of activity set points, demonstrate the differential regulation of set points and compensatory mechanisms, and propose a new strategy to treat epilepsy.

Hypothalamic Agrp neurons regulate food ingestion in adult mice. Whether these neurons are functional before animals start to ingest food is unknown. Here, we studied the functional ontogeny of Agrp neurons during breastfeeding using postnatal day 10 mice. In contrast to adult mice, we show that isolation from the nursing nest, not milk deprivation or ingestion, activated Agrp neurons. Non-nutritive suckling and warm temperatures blunted this effect. Using in vivo fiber photometry, neonatal Agrp neurons showed a rapid increase in activity upon isolation from the nest, an effect rapidly diminished following reunion with littermates. Neonates unable to release GABA from Agrp neurons expressed blunted emission of isolation-induced ultrasonic vocalizations. Chemogenetic overactivation of these neurons further increased emission of these ultrasonic vocalizations, but not milk ingestion. We uncovered important functional properties of hypothalamic Agrp neurons during mouse development, suggesting these neurons facilitate offspring-to-caregiver bonding.

Background: Cisplatin is an extensively used anti-neoplastic agent for the treatment of various solid tumors. However, a high incidence of severe ototoxicity is accompanied by its use in the clinic. Currently, no drugs or therapeutic strategies have been approved for the treatment of cisplatin-induced ototoxicity by the FDA. Purpose: The purpose of this study was to investigate the otoprotective effects of dexamethasone (DEX)-loaded silk-polyethylene hydrogel (DEX-SILK) following round window membrane administration in the cisplatin-induced ototoxicity mouse model. Methods: The morphology, gelation kinetics, viscosity and secondary structure of the DEX-SILK hydrogel were analyzed. DEX concentration in the perilymph was tested at different time points following hydrogel injection on the RWM niche. Cultured cells (HEI-OC1), organ of Corti explants (C57/BL6, P0-2), and cisplatin-induced hearing loss mice model (C57/BL6) were used as in vitro and in vivo models for investigating the otoprotective effects of DEX-SILK hydrogel against cisplatin. Results: Encapsulation of DEX with a loading of 8% (w/v) did not significantly change the silk gelation time, and DEX was evenly distributed in the Silk-PEG hydrogel as visualized by scanning electron microscopy (SEM). The concentration of Silk majorly influenced DEX distribution, morphological characteristics, viscosity, and gelation time. The optimized DEX-SILK hydrogel (8% w/v loading, 15% silk concentration, 10 μl) was administered directly onto the RWM of the guinea pigs. The DEX concentration in the perilymph was maintained above 1 μg/ml for at least 21 days for the DEX-SILK, while it was maintained for less than 6 h in the control sample of free DEX. DEX-SILK (5-60 ng/ml) exhibited significant protective effects against cisplatin-induced cellular ototoxicity and notably reduced the production of reactive oxygen species (ROS). Eventually, pretreatment with DEX-SILK effectively preserved outer hair cells in the cultured organ of Corti explants and demonstrated significant hearing protection at 4, 8, and 16 kHz in the cisplatin-induced hearing loss mice as compared to the effects noted following pretreatment with DEX. Conclusion: These results demonstrated the clinical value of DEX-SILK for the therapy of cisplatin-induced ototoxicity.

Tactile working memory engages a broad network of cortical regions in primates. To assess whether the conclusions drawn from primates apply to rodents, we examined the vibrissal primary somatosensory cortex (vS1) and the prelimbic cortex (PL) in a delayed comparison task. Rats compared the speeds of two vibrissal vibrations, stimulus1 and stimulus2, separated by a delay of 2 s. Neuronal firing rates in vS1 and PL encode both stimuli in real time. Across the delay, the stimulus1 representation declines more precipitously in vS1 than in PL. Theta-band local field potential (LFP) coherence between vS1 and PL peaks at trial onset and remains elevated during the interstimulus interval; simultaneously, vS1 spikes become phase locked to PL LFP. Phase locking is stronger on correct (versus error) trials. Tactile working memory in rats appears to be mediated by a posterior (vS1) to anterior (PL) flow of information, with performance facilitated through coherent LFP oscillation.

Background: Cervical vestibular evoked myogenic potential (cVEMP) testing is a strong tool that enables objective determination of balance functions in humans. However, it remains unknown whether cVEMP correctly expresses vestibular disorder in mice. Objective: In this study, correlations of cVEMP with scores for balance-related behavior tests including rotarod, beam, and air-righting reflex tests were determined in ICR mice with vestibular disorder induced by 3,3'-iminodipropiontrile (IDPN) as a mouse model of vestibular disorder. Methods: Male ICR mice at 4 weeks of age were orally administered IDPN in saline (28 mmol/kg body weight) once. Rotarod, beam crossing, and air-righting reflex tests were performed before and 3-4 days after oral exposure one time to IDPN to determine balance functions. The saccule and utricles were labeled with fluorescein phalloidin. cVEMP measurements were performed for mice in the control and IDPN groups. Finally, the correlations between the scores of behavior tests and the amplitude or latency of cVEMP were determined with Spearman's rank correlation coefficient. Two-tailed Student's t test and Welch's t test were used to determine a significant difference between the two groups. A difference with p < 0.05 was considered to indicate statistical significance. Results: After oral administration of IDPN at 28 mmol/kg, scores of the rotarod, beam, and air-righting reflex tests in the IDPN group were significantly lower than those in the control group. The numbers of hair cells in the saccule, utricle, and cupula were decreased in the IDPN group. cVEMP in the IDPN group was significantly decreased in amplitude and increased in latency compared to those in the control group. cVEMP amplitude had significant correlations with the numbers of hair cells as well as scores for all of the behavior tests in mice. Conclusions: This study demonstrated impaired cVEMP and correlations of cVEMP with imbalance determined by behavior tests in a mouse model of vestibular disorder.

Mechanical displacements of the basilar membrane (BM) and the electrophysiological responses of the auditory outer hair cells (OHCs) are key components of the frequency tuning and cochlear amplification in the mammalian cochlea. In the work presented here, we measured the responses of (1) the extracellular voltage generated by OHCs (VOHC) and (2) displacements within the organ of Corti complex (OCC) to a multi-tone stimulus, and to single tones. Using optical coherence tomography (OCT), we were able to measure displacements of different layers in the OCC simultaneously, in the base of the gerbil cochlea. We explored the effect of the two types of sound stimuli to the nonlinear behavior of voltage and displacement in two frequency regions: a frequency region below the BM nonlinearity (sub-BF region: f < ∼0.7 BF), and in the best frequency (BF) region. In the sub-BF region, BM motion (XBM) had linear growth for both stimulus types, and the motion in the OHC region (XOHC) was mildly nonlinear for single tones, and relatively strongly nonlinear for multi-tones. Sub-BF, the nonlinear character of VOHC was similar to that of XOHC. In the BF region XBM, VOHC and XOHC all possessed the now-classic nonlinearity of the BF peak. Coupling these observations with previous findings on phasing between OHC force and traveling wave motions, we propose the following framework for cochlear nonlinearity: The BF-region nonlinearity is an amplifying nonlinearity, in which OHC forces input power into the traveling wave, allowing it to travel further apical to the region where it peaks. The sub-BF nonlinearity is a non-amplifying nonlinearity; it represents OHC electromotility, and saturates due to OHC current saturation, but the OHC forces do not possess the proper phasing to feed power into the traveling wave.

Human listeners are able to recognize accurately an impressive range of complex sounds, such as musical instruments or voices. The underlying mechanisms are still poorly understood. Here, we aimed to characterize the processing time needed to recognize a natural sound. To do so, by analogy with the “rapid visual sequential presentation paradigm”, we embedded short target sounds within rapid sequences of distractor sounds. The core hypothesis is that any correct report of the target implies that sufficient processing for recognition had been completed before the time of occurrence of the subsequent distractor sound. We conducted four behavioral experiments using short natural sounds (voices and instruments) as targets or distractors. We report the effects on performance, as measured by the fastest presentation rate for recognition, of sound duration, number of sounds in a sequence, the relative pitch between target and distractors and target position in the sequence. Results showed a very rapid auditory recognition of natural sounds in all cases. Targets could be recognized at rates up to 30 sounds per second. In addition, the best performance was observed for voices in sequences of instruments. These results give new insights about the remarkable efficiency of timbre processing in humans, using an original behavioral paradigm to provide strong constraints on future neural models of sound recognition.