Auditory System Research Articles

Noise schemas aid hearing in noise

Human hearing is robust to noise, but the basis of this robustness is poorly understood. Several lines of evidence are consistent with the idea that the auditory system adapts to sound components that are stable over time, potentially achieving noise robustness by suppressing noise-like signals. Yet background noise often provides behaviorally relevant information about the environment and thus seems unlikely to be completely discarded by the auditory system. Motivated by this observation, we explored whether noise robustness might instead be mediated by internal models of noise structure that could facilitate the separation of background noise from other sounds. We found that detection, recognition, and localization in real-world background noise were better for foreground sounds positioned later in a noise excerpt, with performance improving over the initial second of exposure to a noise. These results are consistent with both adaptation-based and model-based accounts (adaptation increases over time and online noise estimation should benefit from acquiring more samples). However, performance was also robust to interruptions in the background noise and was enhanced for intermittently recurring backgrounds, neither of which would be expected from known forms of adaptation. Additionally, the performance benefit observed for foreground sounds occurring later within a noise excerpt was reduced for recurring noises, suggesting that a noise representation is built up during exposure to a new background noise and then maintained in memory. These findings suggest that noise robustness is supported by internal models-"noise schemas"-that are rapidly estimated, stored over time, and used to estimate other concurrent sounds.

Sound therapy in the treotment of tinnitus

Tinnitus is currently a serious problem of rhinolaryngology, leads to a significant decrease in the quality of human life, limits his ability to household, social and professional activities. It has a high prevalence and occurs in 10-15% of the adult population, while in 1-3% of cases a severe form of the disease is observed. There are more than 60 treatments for ear noise in the world. These include drug therapy; physiotherapeutic effects that allow stimulating various parts of the auditory pathway from the hair cells of the cochlea, the nuclei of the brain stem, the medulla oblongata, the temporal gyri of the cerebral cortex; sound therapy, as well as the use of technical means audio maskers, hearing aids, implants. The aim of this review is to highlight the current state of the issue, to analyze the sound-activating methods of rehabilitation of patients with tinnitus proposed in world practice. Such a variety of techniques is due to the polyethological nature of the factors causing tinnitus and the empirical approach to treatment. A significant arsenal of medications and surgical interventions used to treat pathological auditory sensations often turns out to be far from universal and often ineffective. It should be noted that with an increase in the prescription of subjective tinnitus, the effectiveness of drug therapy decreases and, in turn, the importance of rehabilitation therapies increases. Most modern methods of treating this pathology are based on the principles of neuroplasticity the ability of the central nervous system to structurally and functionally reorganize. Recently, much attention has been paid to non-drug treatment methods, including the method of reeducation (sound therapy).

Neural speech tracking and auditory attention decoding in everyday life

IntroductionIn our complex world, the auditory system plays a crucial role in perceiving and processing our environment. Humans are able to segment and stream concurrent auditory objects, allowing them to focus on specific sounds, such as speech, and suppress irrelevant auditory objects. The attentional enhancement or suppression of sound processing is evident in neural data through a phenomenon called neural speech tracking. Previous studies have identified correlates of neural speech tracking in electroencephalography (EEG) data, but EEG measures are susceptible to motion artefacts, and the association between neural data and auditory objects is vulnerable to distraction.MethodsThe current study investigated EEG-based auditory attention decoding in realistic everyday scenarios. N=20 participants were exposed to the sound of a busy cafeteria or walked along busy and quiet streets while listening to one or two simultaneous speech streams. We also investigated the robustness of neural speech tracking estimates within subjects. Linear decoding models were used to determine the magnitude of neural speech tracking.ResultsThe results confirmed that neural speech tracking was strongest in single speaker scenarios. In dual speaker conditions, there was significantly stronger neural speech tracking for the attended speaker compared to the ignored speaker, even in complex environments such as a busy cafeteria or outdoor settings.DiscussionIn conclusion, EEG-based attention decoding is feasible in highly complex and realistic everyday conditions while humans behave naturally.

Functional localization of the human auditory and visual thalamus using a thalamic localizer functional magnetic resonance imaging task

Abstract Functional magnetic resonance imaging (fMRI) of the auditory and visual sensory systems of the human brain is an active area of investigation in the study of human health and disease. The medial geniculate nucleus (MGN) and lateral geniculate nucleus (LGN) are key thalamic nuclei involved in the processing and relay of auditory and visual information, respectively, and are the subject of blood-oxygen-level-dependent (BOLD) fMRI studies of neural activation and functional connectivity in human participants. However, localization of BOLD fMRI signal originating from neural activity in MGN and LGN remains a technical challenge, due, in part, to the poor definition of boundaries of these thalamic nuclei in standard T1-weighted and T2-weighted magnetic resonance imaging sequences. Here, we report the development and evaluation of an auditory and visual sensory thalamic localizer (TL) fMRI task that produces participant-specific functionally-defined regions of interest (fROIs) of both MGN and LGN, using 3 Tesla multiband fMRI and a clustered-sparse temporal acquisition sequence, in less than 16 minutes of scan time. We demonstrate the use of MGN and LGN fROIs obtained from the TL fMRI task in standard resting-state functional connectivity (RSFC) fMRI analyses in the same participants. In RSFC analyses, we validated the specificity of MGN and LGN fROIs for signals obtained from primary auditory and visual cortex, respectively, and benchmarked their performance against alternative atlas- and segmentation-based localization methods. The TL fMRI task and analysis code (written in Presentation and MATLAB, respectively) have been made freely available to the wider research community.

Psychoacoustic and Archeoacoustic nature of ancient Aztec skull whistles.

Many ancient cultures used musical tools for social and ritual procedures, with the Aztec skull whistle being a unique exemplar from postclassic Mesoamerica. Skull whistles can produce softer hiss-like but also aversive and scream-like sounds that were potentially meaningful either for sacrificial practices, mythological symbolism, or intimidating warfare of the Aztecs. However, solid psychoacoustic evidence for any theory is missing, especially how human listeners cognitively and affectively respond to skull whistle sounds. Using psychoacoustic listening and classification experiments, we show that skull whistle sounds are predominantly perceived as aversive and scary and as having a hybrid natural-artificial origin. Skull whistle sounds attract mental attention byaffectively mimicking other aversive and startling sounds produced by nature and technology. They were psychoacoustically classified as a hybrid mix of being voice- and scream-like but also originating from technical mechanisms. Using human neuroimaging, we furthermore found that skull whistle sounds received a specific decoding of the affective significance in the neural auditory system of human listeners, accompanied by higher-order auditory cognition and symbolic evaluations in fronto-insular-parietal brain systems. Skull whistles thus seem unique sound tools with specific psycho-affective effects on listeners, and Aztec communities might have capitalized on the scary and scream-like nature of skull whistles.

A Rare Neck Lesion in Children: Bilateral Chondrocutaneous Branchial Remnant.

Cervical chondrocutaneous branchial remnant is a rare congenital developmental anomaly typically located on the lateral neck. Histologically, it has the appearance of an accessory tragus demonstrating a central cartilaginous core with surrounding fibrosis located in the subcutaneous tissue. In order to address the clinical and therapeutic aspects of cervical chondrocutaneous branchial remnants in children, a 6-year-old boy who presents with bilateral hard cervical masses at the lower region of the neck is presented. Chondrocutaneous branchial remnant is a very rare cervical lesion in children, and surgical excision is the only choice of treatment. Cervical chondrocutaneous branchial remnant has been associated with a variety of congenital anomalies, particularly involving the auditory, cardiovascular, and visual systems. Despite bilateral occurrence of cervical chondrocutaneous branchial remnant, our patient had no cardiac or genitourinary anomalies.

Does age protect against loss of tonotopy after acute deafness in adulthood?

The mammalian auditory system develops a topographical representation of sound frequencies along its pathways, also called tonotopy. In contrast, sensory deprivation during early development results in no or only rudimentary tonotopic organization. This study addresses two questions: (1) How robust is the central tonotopy when hearing fails in adulthood? (2) What role does age play at time of deafness? To address these questions, we deafened young and old adult rats with previously normal hearing. One month after deafening, both groups were unilaterally supplied with cochlear implants and electrically stimulated for 2 h. The central auditory neurons, which were activated as a result of the local electrical intracochlear stimulation, were visualized using Fos staining. While the auditory system of young rats lost the tonotopic organization throughout the brainstem, the auditory system of the older rats mainly sustained its tonotopy. It can be proposed that plasticity prevails in the central auditory system of young adult rats, while network stability prevails in the brains of aging rats. Consequently, age may be an important factor in protecting a hearing-experienced adult auditory system from a rapid loss of tonotopy when suffering from acute hearing loss. Furthermore, the study provides compelling evidence that acute deafness in young adult patients should be diagnosed as early as possible to prevent maladaptation of the central auditory system and thus achieve the optimal hearing outcome with a hearing prosthesis.

Direct piriform-to-auditory cortical projections shape auditory-olfactory integration.

In a real-world environment, the brain must integrate information from multiple sensory modalities, including the auditory and olfactory systems. However, little is known about the neuronal circuits governing how odors influence and modulate sound processing. Here, we investigated the mechanisms underlying auditory-olfactory integration using anatomical, electrophysiological, and optogenetic approaches, focusing on the auditory cortex as a key locus for cross-modal integration. First, retrograde and anterograde viral tracing strategies revealed a direct projection from the piriform cortex to the auditory cortex. Next, using in vivo electrophysiological recordings of neuronal activity in the auditory cortex of awake male or female mice, we found that odors modulate auditory cortical responses to sound. Finally, we used in vivo optogenetic manipulations during electrophysiology to demonstrate that olfactory modulation in auditory cortex, specifically, odor-driven enhancement of sound responses, depends on direct input from the piriform cortex. Together, our results identify a novel role of piriform-to-auditory cortical circuitry in shaping olfactory modulation in the auditory cortex, shedding new light on the neuronal mechanisms underlying auditory-olfactory integration.Significance Statement All living organisms exist within multisensory environments, yet there is a lack in our understanding of how the brain integrates multisensory information. This work highlights a direct piriform-to-auditory cortical circuit governing auditory-olfactory integration. Our results shed new light on a relatively understudied area of multisensory research, promising a more robust understanding of how animals and humans perceive and interact within complex environments.

Hypoxia adaptation mechanism in rats’ peripheral auditory system in high altitude migration: a time series transcriptome analysis

High altitude is characterized by low oxygen, low pressure, and high radiation. When migrates from low to high altitudes, the body’s tissues and organs experience hypoxic stress and will present acoustic adaptation as the protective response. However, the mechanisms of acoustic adaptation at high altitudes remain unclear. In this study, cochlear tissues from Wistar rats were collected at 15, 30, 60, 120, and 180 days after high-altitude migration. Transcriptome sequencing was conducted and DESeq algorithm revealed expression patterns of Differentially Expressed Genes(DEGs) after high altitude migration. Day 60 is a critical stage for cochlear tissue “damage” and “repair” in high-altitude conditions. Transmission Electron Microscopy (TEM) observations of structures also support the findings. A time-series gene co-expression network algorithm was used to investigate gene regulatory patterns and key genes after migration. Immunofluorescence, immunohistochemistry, and qPCR were per-formed for key gene validation and localization. At Day 60, the peak DEG count occurs in rats migrating to high altitude, aligning with the critical phase for cochlear tissue damage and repair at high altitudes. Repair hinges on synaptic plasticity and myelination-linked processes, influencing modules M4 to M6. Module M4’s activation gradually diminishes from its peak. However, the ‘damage’ effect is orchestrated by inflammation-related processes in modules M3 to M5, with module M3’s activation also waning. Key gene module M4, pivotal for repair during this pivotal phase, encompasses Sptbn5, Cldn1, Gfra2, and Lims2 as its core genes. Immunohistochemistry reveals Sptbn5’s presence in cochlear neurons, hair cells, Schwann cells and stria vascularis tissue. Cldn1 and Gfra2 predominantly localize within the cochlear neuron region. These results may suggest new directions for future research on acoustic acclimatization to high altitude.

Neuroanatomical correlates of subjective tinnitus: insights from advanced cortical morphology analysis.

Subjective tinnitus, characterized by the perception of phantom sounds in the absence of external stimuli, presents significant challenges in both audiology and neurology. Once thought to primarily involve aberrant neural activity within auditory pathways, it is now understood to engage a broader array of neuroanatomical structures. This study investigated the connections between auditory, cognitive, and sensory processing regions, which are crucial for unraveling the complex neurobiological basis of tinnitus. Using high-resolution T1-weighted magnetic resonance imaging, we compared 52 individuals with subjective tinnitus with 52 age-matched healthy controls, focusing on cerebral cortex features, including fractal dimensionality, gyrification, and sulcal depth. Covariate analyses were conducted to explore the relationships between tinnitus duration, Tinnitus Handicap Inventory scores, anxiety score, and neuroanatomical changes. We found significant alterations in key brain regions involved in sensory processing, cognition, and emotional regulation, including the insula, lateral occipital cortex, middle frontal gyrus, and superior parietal lobule. These neuroanatomical changes were strongly correlated with the severity and chronicity of tinnitus symptoms. Our findings reveal profound structural changes in the brain associated with subjective tinnitus, offering valuable insights into the condition's underlying mechanisms and providing a potential framework for guiding future research and therapeutic interventions.

Developmental encoding of natural sounds in the mouse auditory cortex.

Mice communicate through high-frequency ultrasonic vocalizations, which are crucial for social interactions such as courtship and aggression. Although ultrasonic vocalization representation has been found in adult brain areas along the auditory pathway, including the auditory cortex, no evidence is available on the neuronal representation of ultrasonic vocalizations early in life. Using in vivo two-photon calcium imaging, we analyzed auditory cortex layer 2/3 neuronal responses to USVs, pure tones (4 to 90kHz), and high-frequency modulated sweeps from postnatal day 12 (P12) to P21. We found that ACx neurons are tuned to respond to ultrasonic vocalization syllables as early as P12 to P13, with an increasing number of responsive cells as the mouse age. By P14, while pure tone responses showed a frequency preference, no syllable preference was observed. Additionally, at P14, USVs, pure tones, and modulated sweeps activate clusters of largely nonoverlapping responsive neurons. Finally, we show that while cell correlation decreases with increasing processing of peripheral auditory stimuli, neurons responding to the same stimulus maintain highly correlated spontaneous activity after circuits have attained mature organization, forming neuronal subnetworks sharing similar functional properties.

From oxygen shortage to neurocognitive challenges: behavioral patterns and imaging insights

Environmental hypoxia, resulting from reduced oxygen supply, poses a significant risk of dysfunctioning and damaging the neurocognitive system, particularly in relation to anxiety and stress. Inadequate oxygenation can lead to acute and chronic brain damage. Scholars used behavioral, hemodynamic, and electromagnetic neurofunctional techniques to investigate the effects of normobaric and hypobaric hypoxia on neurocognitive systems. They found a correlation between hypoxia, altered psychomotor responses, and changes in EEG alpha, theta, beta, and gamma rhythms, which affect spatial attention and memory. Hypoxia affects event related potential (ERP) components differently depending on latency. Perceptual responses N1 and P2 remain largely unaffected, while the amplitudes of preattentive MMN, vMMN, and P3a are significantly altered. Late latency components related to attention, particularly P3b, are also altered. These changes illustrate the spectrum from sensory detection to more complex cognitive processing, highlighting the brain's efficiency in managing information. Interestingly, the amplitudes of P3b, ADAN and CNV can increase with increased cognitive demands in hypoxia. This suggests a compensatory response. Prolonged exposure exacerbates these effects, resulting in compensatory delayed behavioral responses and alterations in behavioral monitoring and conflict inhibitory control, as reflected by reduced amplitudes in some attention related ERP components, including N2, N2pc, and ERN. Thus, neurocognitive function and integrity are under stress. ERP sources and hemodynamic images reveal that vulnerable brain regions include the frontal prefrontal cortices, hippocampus, basal ganglia, and parietal and visual cortices, which are essential for attention related processes like decision making and spatial memory. The auditory system appears less affected.

Enhanced auditory responses in visual cortex of blind rats using intrinsic optical signal imaging

Functional maturation of the visual cortex is induced by visual experiences during critical periods. Blind animals and humans exhibit improved auditory abilities after losing their vision. Here we investigated the response of the visual cortex to white noise stimuli during the progression of photoreceptor degeneration in a rat model of blindness (Royal College of Surgeons [RCS] (rdy/rdy) rats). Optical coherence tomography of RCS (+/+) rats with normal visual function revealed normal photoreceptor cells, whereas 3-month-old RCS (rdy/rdy) rats demonstrated photoreceptor cell degeneration. Visual cortex responses (VCRs) to a single flash stimulus were negligible in 3-month-old photoreceptor-degenerated rats. However, VCRs with white noise stimuli were significantly increased in blind versus RCS rats (+/+). Slight changes in the intrinsic optical signals of the control rats were observed on the ventral side of the visual cortex. In contrast, responses were markedly increased throughout the visual cortex of RCS (rdy/rdy) rats. These results indicate that the visual cortex rapidly acquires auditory system function over the first 3 months of life and that the entire visual cortex, rather than just the portion close to the auditory cortex, responds to white noise.

Recognition and classification of noise signals by dolphins under conditions of noise interference and spatial uncertainty of their simultaneous presentation

The ability of dolphin`s auditory system to recognize and classify noise signals according to certain invariant features under the influence of noise interference and spatial uncertainty of their simultaneous presentation was studied. The bottlenose dolphins trained to differentiate such signals had to solve this problem under conditions simulating real marine ones, when the perception of a useful signal occurs against the background of similar signals and noise interference. First, the noise signals were sequentially presented to the animal against the background of white masking noise. Further the dolphin had to identify a signal of a positive class from several simultaneously sounding sound sources. The efficiency of the animal was evaluated at several given levels of noise interference. In this case, the actual noise interference was both white noise and simultaneously sounding negative signals. It`s shown that the efficiency and noise immunity of dolphin`s auditory system depend on the degree of alternativeness of the spatial uncertainty of the simultaneous presentation of signals.

MYH1 deficiency disrupts outer hair cell electromotility, resulting in hearing loss.

Myh1 is a mouse deafness gene with an unknown function in the auditory system. Hearing loss in Myh1-knockout mice is characterized by an elevated threshold for the auditory brainstem response and the absence of a threshold for distortion product otoacoustic emission. Here, we investigated the role of MYH1 in outer hair cells (OHCs), crucial structures in the organ of Corti responsible for regulating cochlear amplification. Direct whole-cell voltage-clamp recordings of OHCs revealed that prestin activity was lower in Myh1-knockout mice than in wild-type mice, indicating abnormal OHC electromotility. We analyzed whole-exome sequencing data from 437 patients with hearing loss of unknown genetic causes and identified biallelic missense variants of MYH1 in five unrelated families. Hearing loss in individuals harboring biallelic MYH1 variants was non-progressive, with an onset ranging from congenital to childhood. Three of five individuals with MYH1 variants displayed osteopenia. Structural prediction by AlphaFold2 followed by molecular dynamic simulations revealed that the identified variants presented structural abnormalities compared with wild-type MYH1. In a heterogeneous overexpression system, MYH1 variants, particularly those in the head domain, abolished MYH1 functions, such as by increasing prestin activity and modulating the membrane traction force. Overall, our findings suggest an essential function of MYH1 in OHCs, as observed in Myh1-deficient mice, and provide genetic evidence linking biallelic MYH1 variants to autosomal recessive hearing loss in humans.

Effects of the two-pore potassium channel subunit Task5 on neuronal function and signal processing in the auditory brainstem

Processing of auditory signals critically depends on the neuron’s ability to fire brief, precisely timed action potentials (APs) at high frequencies and high fidelity for prolonged times. This requires the expression of specialized sets of ion channels to quickly repolarize neurons, prevent aberrant AP firing and tightly regulate neuronal excitability. Although critically important, the regulation of neuronal excitability has received little attention in the auditory system. Neuronal excitability is determined to a large extent by the resting membrane potential (RMP), which in turn depends on the kind and number of ion channels open at rest; mostly potassium channels. A large part of this resting potassium conductance is carried by two-pore potassium channels (K2P channels). Among the K2P channels, the subunit Task5 is expressed almost exclusively in the auditory brainstem, suggesting a specialized role in auditory processing. However, since it failed to form functional ion channels in heterologous expression systems, it was classified “non-functional” for a long time and its role in the auditory system remained elusive. Here, we generated Task5 knock-out (KO) mice. The loss of Task5 resulted in changes in neuronal excitability in bushy cells of the ventral cochlear nucleus (VCN) and principal neurons of the medial nucleus of the trapezoid body (MNTB). Moreover, auditory brainstem responses (ABRs) to loud sounds were altered in Tasko5-KO mice. Thus, our study provides evidence that Task5 is indeed a functional K2P subunit and contributes to sound processing in the auditory brainstem.

Sensory systems: Geckos shake up our understanding of vertebrate audition

A newly discovered auditory pathway in geckos processes low-frequency vibrations using the saccule, an inner ear organ previously thought to serve only vestibular functions in amniotes. These findings challenge our understanding of hearing evolution and suggest greater conservation of auditory function across vertebrates.

Resistance to age-related hearing loss in the echolocating big brown bat (Eptesicus fuscus).

Hearing mediates many behaviours critical for survival in echolocating bats, including foraging and navigation. Although most mammals are susceptible to progressive age-related hearing loss, the evolution of biosonar, which requires the ability to hear low-intensity echoes from outgoing sonar signals, may have selected against the development of hearing deficits in bats. Many echolocating bats exhibit exceptional longevity and rely on acoustic behaviours for survival to old age; however, relatively little is known about the ageing bat auditory system. In this study, we used DNA methylation to estimate the ages of wild-caught big brown bats (Eptesicus fuscus) and measured hearing sensitivity in young and ageing bats using auditory brainstem responses (ABRs) and distortion product otoacoustic emissions (DPOAEs). We found no evidence for hearing deficits in bats up to 12.5 years of age, demonstrated by comparable thresholds and similar ABR and DPOAE amplitudes across age groups. We additionally found no significant histological evidence for cochlear ageing, with similar hair cell counts, afferent and efferent innervation patterns in young and ageing bats. Here, we demonstrate that big brown bats show minimal evidence for age-related hearing loss and therefore represent informative models for investigating mechanisms that may preserve hearing function over a long lifetime.

Are tinnitus burden and tinnitus exacerbation after cochlear implantation influenced by insertion technique, array dislocation, and intracochlear trauma?

Although numerous studies suggest that cochlear implantation (CI) generally alleviates the overall burden of tinnitus, certain patients experience tinnitus exacerbation following CI. The exact cause of this exacerbation is still uncertain. This prospective study aimed to investigate whether cochlear trauma, resulting from scalar dislocation of the electrode array, affected postoperative tinnitus intensity, tinnitus burden, and speech perception. Additionally, the influence of CI insertion technique, insertion depth, insertion angle, and cochlear morphology on postoperative tinnitus was assessed. We evaluated 66 CI recipients preoperatively at 2 days, 4 weeks, and 12- and 24-months following surgery. Digital volume tomography was employed to document scalar position, insertion depth, and cochlear morphology postoperatively. Speech perception was analyzed using Freiburg monosyllables. The tinnitus burden was evaluated using the tinnitus questionnaire, while the tinnitus intensity was quantified using a visual analog scale. Study results pertaining to tinnitus intensity and burden did not reveal a significant difference in elevation regarding scalar position and dislocation after CI surgery compared to preoperative tinnitus levels. However, dislocation was only identified in four patients, and scala vestibuli insertions were observed in two patients. Comparing preoperative and 1-year postoperative outcomes, CI was noted to substantially reduce the tinnitus burden. When the speech processor was worn, the tinnitus intensity was significantly diminished. In comparison to round window (RW) insertion, the insertion technique cochleostomy (CS) did not exhibit a significant difference or a trend toward increased tinnitus intensity. This study demonstrates that CI significantly decreases the tinnitus burden. The observation implies that the electrical stimulation of the auditory pathway, facilitated by wearing the speech processor, significantly reduced the tinnitus intensity. The incidence of dislocations and scala vestibuli insertions has declined to the extent that it is no longer feasible to formulate statistically significant conclusions.

Musicianship Modulates Cortical Effects of Attention on Processing Musical Triads

Background: Many studies have demonstrated the benefits of long-term music training (i.e., musicianship) on the neural processing of sound, including simple tones and speech. However, the effects of musicianship on the encoding of simultaneously presented pitches, in the form of complex musical chords, is less well established. Presumably, musicians’ stronger familiarity and active experience with tonal music might enhance harmonic pitch representations, perhaps in an attention-dependent manner. Additionally, attention might influence chordal encoding differently across the auditory system. To this end, we explored the effects of long-term music training and attention on the processing of musical chords at the brainstem and cortical levels. Method: Young adult participants were separated into musician and nonmusician groups based on the extent of formal music training. While recording EEG, listeners heard isolated musical triads that differed only in the chordal third: major, minor, and detuned (4% sharper third from major). Participants were asked to correctly identify chords via key press during active stimulus blocks and watched a silent movie during passive blocks. We logged behavioral identification accuracy and reaction times and calculated information transfer based on the behavioral chord confusion patterns. EEG data were analyzed separately to distinguish between cortical (event-related potential, ERP) and subcortical (frequency-following response, FFR) evoked responses. Results: We found musicians were (expectedly) more accurate, though not faster, than nonmusicians in chordal identification. For subcortical FFRs, responses showed stimulus chord effects but no group differences. However, for cortical ERPs, whereas musicians displayed P2 (~150 ms) responses that were invariant to attention, nonmusicians displayed reduced P2 during passive listening. Listeners’ degree of behavioral information transfer (i.e., success in distinguishing chords) was also better in musicians and correlated with their neural differentiation of chords in the ERPs (but not high-frequency FFRs). Conclusions: Our preliminary results suggest long-term music training strengthens even the passive cortical processing of musical sounds, supporting more automated brain processing of musical chords with less reliance on attention. Our results also suggest that the degree to which listeners can behaviorally distinguish chordal triads is directly related to their neural specificity to musical sounds primarily at cortical rather than subcortical levels. FFR attention effects were likely not observed due to the use of high-frequency stimuli (>220 Hz), which restrict FFRs to brainstem sources.