Search

The perception of pitch is a fundamental percept, which is mediated by the auditory system, requiring the abstraction of stimulus properties related to the spectro-temporal structure of sound. Despite its importance, there is still debate as to the precise areas responsible for its encoding, which may be due to species differences or differences in the recording measures and choices of stimuli used in previous studies. Moreover, it was unknown whether the human brain contains pitch neurons and how distributed such neurons might be. Here, we present the first study to measure multiunit neural activity in response to pitch stimuli in the auditory cortex of intracranially implanted humans. The stimulus sets were regular-interval noise with a pitch strength that is related to the temporal regularity and a pitch value determined by the repetition rate and harmonic complexes. Specifically, we demonstrate reliable responses to these different pitch-inducing paradigms that are distributed throughout Heschl’s gyrus, rather than being localized to a particular region, and this finding was evident regardless of the stimulus presented. These data provide a bridge across animal and human studies and aid our understanding of the processing of a critical percept associated with acoustic stimuli.

BackgroundMisophonia is often referred to as a disorder that is characterized by excessive negative emotional responses, including anger and anxiety, to “trigger sounds” which are typically day-to-day sounds, such as those generated from people eating, chewing, and breathing. Misophonia (literally ‘hatred of sounds’) has commonly been understood within an auditory processing framework where sounds cause distress due to aberrant processing in the auditory and emotional systems of the brain. However, recent evidence from brain imaging showing involvement of the motor system while listening to trigger sounds suggests that it is the perception of action (e.g., mouth movement) of the trigger person, and not the sounds per se, that drives the distress in misophonia. Since observation or listening to sounds of actions of others are known to prompt automatic mimicry/imitations in perceivers, we hypothesized that mimicking the action of the trigger person may be prevalent in misophonia. Apart from a few case studies and anecdotal information, a relation between mimicking and misophonia has not been systematically evaluated. MethodIn this work, we addressed this limitation by collecting data on misophonia symptoms and mimicry behaviour using online questionnaires from 676 participants. ResultsAnalysis of these data shows that (i) the tendency to mimic varies in direct proportion to misophonia severity assessed using a self-reported questionnaire, (ii) compared to other human and environmental sounds, trigger sounds of eating and chewing are more likely to trigger mimicking, and (iii) the act of mimicking provides relief from distress to most people with misophonia. LimitationsThe format of the study as an online survey used questionnaires to assess misophonia status. The questionnaire has been used extensively in misophonia research, however it is not fully validated for use in clinical populations, therefore we cannot be certain on the degree of severity of symptoms reported in this study population.ConclusionThis study shows that mimicry is widely prevalent in misophonia and is elicited by the most common trigger sounds of eating and chewing. These data reinforce the idea of hyper-mirroring in misophonia proposed in our earlier work (Kumar et al., 2021). Thus, providing crucial implications for how we treat and interpret misophonia moving forward.

Misophonia is a common disorder characterized by the experience of strong negative emotions of anger and anxiety in response to certain everyday sounds, such as those generated by other people eating, drinking, and breathing. The commonplace nature of these “trigger” sounds makes misophonia a devastating disorder for sufferers and their families. How such innocuous sounds trigger this response is unknown. Since most trigger sounds are generated by orofacial movements (e.g., chewing) in others, we hypothesized that the mirror neuron system related to orofacial movements could underlie misophonia. We analyzed resting state fMRI (rs-fMRI) connectivity (N = 33, 16 females) and sound-evoked fMRI responses (N = 42, 29 females) in misophonia sufferers and controls. We demonstrate that, compared with controls, the misophonia group show no difference in auditory cortex responses to trigger sounds, but do show: (1) stronger rs-fMRI connectivity between both auditory and visual cortex and the ventral premotor cortex responsible for orofacial movements; (2) stronger functional connectivity between the auditory cortex and orofacial motor area during sound perception in general; and (3) stronger activation of the orofacial motor area, specifically, in response to trigger sounds. Our results support a model of misophonia based on “hyper-mirroring” of the orofacial actions of others with sounds being the “medium” via which action of others is excessively mirrored. Misophonia is therefore not an abreaction to sounds, per se, but a manifestation of activity in parts of the motor system involved in producing those sounds. This new framework to understand misophonia can explain behavioral and emotional responses and has important consequences for devising effective therapies. SIGNIFICANCE STATEMENT Conventionally, misophonia, literally “hatred of sounds” has been considered as a disorder of sound emotion processing, in which “simple” eating and chewing sounds produced by others cause negative emotional responses. Our data provide an alternative but complementary perspective on misophonia that emphasizes the action of the trigger-person rather than the sounds which are a byproduct of that action. Sounds, in this new perspective, are only a “medium” via which action of the triggering-person is mirrored onto the listener. This change in perspective has important consequences for devising therapies and treatment methods for misophonia. It suggests that, instead of focusing on sounds, which many existing therapies do, effective therapies should target the brain representation of movement.

Summary Epidemiological studies identify midlife hearing loss as an independent risk factor for dementia, estimated to account for 9% of cases. We evaluate candidate brain bases for this relationship. These bases include a common pathology affecting the ascending auditory pathway and multimodal cortex, depletion of cognitive reserve due to an impoverished listening environment, and the occupation of cognitive resources when listening in difficult conditions. We also put forward an alternate mechanism, drawing on new insights into the role of the medial temporal lobe in auditory cognition. In particular, we consider how aberrant activity in the service of auditory pattern analysis, working memory, and object processing may interact with dementia pathology in people with hearing loss. We highlight how the effect of hearing interventions on dementia depends on the specific mechanism and suggest avenues for work at the molecular, neuronal, and systems levels to pin this down., Griffiths et al. evaluate candidate explanations for the relationship between hearing loss and dementia. As well as considering common pathology, impoverished input, and resource competition, they develop a novel account based on specific interactions between auditory cognition and dementia pathology in the medial temporal lobe.

The perception of pitch requires the abstraction of stimulus properties related to the spectrotemporal structure of sound. Previous studies utilizing both animal electrophysiology and human imaging have indicated the presence of a center for pitch representation in the auditory cortex. Recent data from our own group - examining local field potentials (LFPs) in humans - indicate more widely distributed pitch-associated responses within the auditory cortex (Gander et al., 2019). To probe this with greater spatial resolution, we examined multi-unit activity related to three different auditory stimuli, in seven epilepsy patients who were implanted with high-impedance electrodes in auditory cortex for the clinical purpose of localizing seizures. The stimuli were regular-interval noise (RIN) with a pitch strength that is related to the temporal regularity, and pitch value determined by repetition rate, and harmonic complexes with missing fundamentals. We demonstrated increases in spiking activity in 69 of 104 (66%) responsive multiunit activity in auditory cortex due to pitch-associated stimuli. Importantly, these responses were distributed across the entire extent of Heschl’s gyrus (HG), in both primary and non-primary areas, rather than isolated to a specific region, and this finding was evident regardless of the stimulus presented. These findings are the first multi-unit pitch responses recorded from humans, and align with a recent study in macaques (Kikuchi et al., 2019) demonstrating that both local field potential and unit responses to pitch-inducing stimuli are distributed throughout auditory cortex.Significance StatementThe perception of pitch is a fundamental acoustic attribute that is mediated by the auditory system. Despite its importance, there is still debate as to the precise areas responsible for its encoding, which may be due to differences in the recording measures and choices of stimuli used in previous studies. Here, we present the first study to measure multi-unit pitch responses in the auditory cortices of intracranially-implanted humans. Importantly, we demonstrate reliable responses to three different pitch-inducing paradigms that are distributed throughout Heschl’s gyrus, rather than being localized to a particular region. These data provide a bridge across animal and human studies, and aid in our understanding of the processing of a critical attribute of acoustic stimuli.

Auditory object analysis requires the fundamental perceptual process of detecting boundaries between auditory objects. However, the dynamics underlying the identification of discontinuities at object boundaries are not well understood. Here, we employed a synthetic stimulus composed of frequency-modulated ramps known as 'acoustic textures', where boundaries were created by changing the underlying spectrotemporal statistics. We collected magnetoencephalographic (MEG) data from human volunteers and observed a slow (

Musical engagement may be associated with better listening skills, such as the perception of and working memory for notes, in addition to the appreciation of musical rules. The nature and extent of this association is controversial. In this study we assessed the relationship between musical engagement and both sound perception and working memory. We developed a task to measure auditory perception and working memory for sound using a behavioural measure for both, precision. We measured the correlation between these tasks and musical sophistication based on a validated measure (the Goldsmiths Musical Sophistication Index) that can be applied to populations of both musicians and non-musicians. The data show that musical sophistication accounts for 21% of the variance in the precision of working memory for frequency in an analysis that accounts for age and non-verbal intelligence. Musical sophistication was not significantly associated with the precision of working memory for amplitude modulation rate or with the precision of perception of either acoustic feature. The work supports a specific association between musical sophistication and working memory for sound frequency.

Misophonia is a disorder of decreased tolerance to specific sounds or their associated stimuli that has been characterized using different language and methodologies. The absence of a common understanding or foundational definition of misophonia hinders progress in research to understand the disorder and develop effective treatments for individuals suffering from misophonia. From June 2020 through January 2021, a project was conducted to determine whether a committee of experts with diverse expertise related to misophonia could develop a consensus definition of misophonia. An expert committee used a modified Delphi method to evaluate candidate definitional statements that were identified through a systematic review of the published literature. Over four rounds of iterative voting, revision, and exclusion, the committee made decisions to include, exclude, or revise these statements in the definition based on the currently available scientific and clinical evidence. A definitional statement was included in the final definition only after reaching consensus at 80% or more of the committee agreeing with its premise and phrasing. The results of this rigorous consensus-building process were compiled into a final definition of misophonia that is presented here. This definition will serve as an important step to bring cohesion to the growing field of researchers and clinicians who seek to better understand and support individuals experiencing misophonia.

This work examines how sounds are held in auditory working memory (AWM) in humans by examining oscillatory local field potentials (LFPs) in candidate brain regions. Previous fMRI studies by our group demonstrated blood oxygenation level-dependent (BOLD) response increases during maintenance in auditory cortex, inferior frontal cortex and the hippocampus using a paradigm with a delay period greater than 10s. The relationship between such BOLD changes and ensemble activity in different frequency bands is complex, and the long delay period raised the possibility that long-term memory mechanisms were engaged. Here we assessed LFPs in different frequency bands in six subjects with recordings from all candidate brain regions using a paradigm with a short delay period of 3 s. Sustained delay activity was demonstrated in all areas, with different patterns in the different areas. Enhancement in low frequency (delta) power and suppression across higher frequencies (beta/gamma) were demonstrated in primary auditory cortex in medial Heschl’s gyrus (HG) whilst non-primary cortex showed patterns of enhancement and suppression that altered at different levels of the auditory hierarchy from lateral HG to superior- and middle-temporal gyrus. Inferior frontal cortex showed increasing suppression with increasing frequency. The hippocampus and parahippocampal gyrus showed low frequency increases and high frequency decreases in oscillatory activity. This work demonstrates sustained activity patterns during AWM maintenance, with prominent low-frequency increases in medial temporal lobe regions., Highlights • Local field potentials recorded in humans while they keep sound in working memory. • Sustained increase in delta power observed in primary auditory cortex. • Pattern of change in power in non-primary cortex depends on the hierarchical level. • Hippocampus and parahippocampus showed increase in low frequency power.

Using fMRI and multivariate pattern analysis, we determined whether spectral and temporal acoustic features are represented by independent or integrated multivoxel codes in human cortex. Listeners heard band-pass noise varying in frequency (spectral) and amplitude-modulation (AM) rate (temporal) features. In the superior temporal plane, changes in multivoxel activity due to frequency were largely invariant with respect to AM rate (and vice versa), consistent with an independent representation. In contrast, in posterior parietal cortex, multivoxel representation was exclusively integrated and tuned to specific conjunctions of frequency and AM features (albeit weakly). Direct between-region comparisons show that whereas independent coding of frequency weakened with increasing levels of the hierarchy, such a progression for AM and integrated coding was less fine-grained and only evident in the higher hierarchical levels from non-core to parietal cortex (with AM coding weakening and integrated coding strengthening). Our findings support the notion that primary auditory cortex can represent spectral and temporal acoustic features in an independent fashion and suggest a role for parietal cortex in feature integration and the structuring of sensory input., Highlights • This study used fMRI and multivariate analysis to examine acoustic feature coding • In auditory cortex, frequency and AM rate were represented primarily independently • In parietal cortex, multivoxel representation was exclusively integrated

This work sought correlates of pitch perception, defined by neural activity above the lower limit of pitch (LLP), in auditory cortical neural ensembles, and examined their topographical distribution. Local field potentials (LFPs) were recorded in eight patients undergoing invasive recordings for pharmaco-resistant epilepsy. Stimuli consisted of bursts of broadband noise followed by regular interval noise (RIN). RIN was presented at rates below and above the LLP to distinguish responses related to the regularity of the stimulus and the presence of pitch itself. LFPs were recorded from human cortical homologues of auditory core, belt, and parabelt regions using multicontact depth electrodes implanted in Heschl’s gyrus (HG) and Planum Temporale (PT), and subdural grid electrodes implanted over lateral superior temporal gyrus (STG). Evoked responses corresponding to the temporal regularity of the stimulus were assessed using autocorrelation of the evoked responses, and occurred for stimuli below and above the LLP. Induced responses throughout the high gamma range (60–200 Hz) were present for pitch values above the LLP, with onset latencies of approximately 70 ms. Mapping of the induced responses onto a common brain space demonstrated variability in the topographical distribution of high gamma responses across subjects. Induced responses were present throughout the length of HG and on PT, which is consistent with previous functional neuroimaging studies. Moreover, in each subject, a region within lateral STG showed robust induced responses at pitch-evoking stimulus rates. This work suggests a distributed representation of pitch processing in neural ensembles in human homologues of core and non-core auditory cortex.

Highlights • We conducted a phenomenological survey comparing musical hallucinations to other inner music. • MH were more likely to be reported as externally located than other experiences. • MH were less controllable and less familiar than imagery or earworms. • MH were less likely to include lyrical content than other forms of inner music. • Individuals with higher levels of musical expertise were less likely to report MH., Musical hallucinations (MH) account for a significant proportion of auditory hallucinations, but there is a relative lack of research into their phenomenology. In contrast, much research has focused on other forms of internally generated musical experience, such as earworms (involuntary and repetitive inner music), showing that they can vary in perceived control, repetitiveness, and in their effect on mood. We conducted a large online survey (N = 270), including 44 participants with MH, asking participants to rate imagery, earworms, or MH on several variables. MH were reported as occurring less frequently, with less controllability, less lyrical content, and lower familiarity, than other forms of inner music. MH were also less likely to be reported by participants with higher levels of musical expertise. The findings are outlined in relation to other forms of hallucinatory experience and inner music, and their implications for psychological models of hallucinations discussed.

The organisation of pitch-perception mechanisms in the primate cortex is controversial, in that divergent results have been obtained, ranging from a single circumscribed ‘pitch centre’ to systems widely distributed across auditory cortex. Possible reasons for such discrepancies include different species, recording techniques, pitch stimuli, sampling of auditory fields, and the neural metrics recorded. In the present study, we sought to bridge some of these divisions by examining activity related to pitch in both neurons and neuronal ensembles within the auditory cortex of the rhesus macaque, a primate species with similar pitch perception and auditory cortical organisation to humans. We demonstrate similar responses, in primary and non-primary auditory cortex, to two different types of broadband pitch above the macaque lower limit in both neurons and local field potential (LFP) gamma oscillations. The majority of broadband pitch responses in neurons and LFP sites did not show equivalent tuning for sine tones.

Auditory figure–ground segregation, listeners' ability to selectively hear out a sound of interest from a background of competing sounds, is a fundamental aspect of scene analysis. In contrast to the disordered acoustic environment we experience during everyday listening, most studies of auditory segregation have used relatively simple, temporally regular signals. We developed a new figure–ground stimulus that incorporates stochastic variation of the figure and background that captures the rich spectrotemporal complexity of natural acoustic scenes. Figure and background signals overlap in spectrotemporal space, but vary in the statistics of fluctuation, such that the only way to extract the figure is by integrating the patterns over time and frequency. Our behavioral results demonstrate that human listeners are remarkably sensitive to the appearance of such figures.In a functional magnetic resonance imaging experiment, aimed at investigating preattentive, stimulus-driven, auditory segregation mechanisms, naive subjects listened to these stimuli while performing an irrelevant task. Results demonstrate significant activations in the intraparietal sulcus (IPS) and the superior temporal sulcus related to bottom-up, stimulus-driven figure–ground decomposition. We did not observe any significant activation in the primary auditory cortex. Our results support a role for automatic, bottom-up mechanisms in the IPS in mediating stimulus-driven, auditory figure–ground segregation, which is consistent with accumulating evidence implicating the IPS in structuring sensory input and perceptual organization.

Generative models, such as predictive coding, posit that perception results from a combination of sensory input and prior prediction, each weighted by its precision (inverse variance), with incongruence between these termed prediction error (deviation from prediction) or surprise (negative log probability of the sensory input). However, direct evidence for such a system, and the physiological basis of its computations, is lacking. Using an auditory stimulus whose pitch value changed according to specific rules, we controlled and separated the three key computational variables underlying perception, and discovered, using direct recordings from human auditory cortex, that surprise due to prediction violations is encoded by local field potential oscillations in the gamma band (>30 Hz), changes to predictions in the beta band (12-30 Hz), and that the precision of predictions appears to quantitatively relate to alpha band oscillations (8-12 Hz). These results confirm oscillatory codes for critical aspects of generative models of perception. DOI: http://dx.doi.org/10.7554/eLife.11476.001, eLife digest Our perception of the world is not only based on input from our senses. Instead, what we perceive is also heavily altered by the context of what is being sensed and our expectations about it. Some researchers have suggested that perception results from combining information from our senses and our predictions. This school of thought, referred to as “predictive coding”, essentially proposed that the brain stores a model of the world and weighs it up against information from our senses in order to determine what we perceive. Nevertheless, direct evidence for the brain working in this way was still missing. While neuroscientists had seen the brain respond when there was a mismatch between an expectation and incoming sensory information, no one has observed the predictions themselves within the brain. Sedley et al. now provide such direct evidence for predictions about upcoming sensory information, by directly recording the electrical activity in the brains of human volunteers who were undergoing surgery for epilepsy. The experiment made use of a new method in which the volunteers listened to a sequence of sounds that was semi-predictable. That is to say that, at first, the volunteers heard a selection of similarly pitched sounds. After random intervals, the average pitch of these sounds changed and they became more or less variable for a while before randomly changing again. This approach meant that the volunteers had to continually update their predictions throughout the experiment In keeping with previous studies, the unexpected sounds, which caused a mismatch between the sensory information and the brain’s prediction, were linked to high-frequency brainwaves. However, Sedley et al. discovered that updating the predictions themselves was linked to middle-frequency brainwaves; this confirms what the predictive coding model had suggested. Finally, this approach also unexpectedly revealed that how confident the volunteer was about the prediction was linked to low-frequency brainwaves. In the future, this new method will provide an easy way of directly studying elements of perception in humans and, since the experiments do not require complex learning, in other animals too. DOI: http://dx.doi.org/10.7554/eLife.11476.002

The brain basis for auditory working memory, the process of actively maintaining sounds in memory over short periods of time, is controversial. Using functional magnetic resonance imaging in human participants, we demonstrate that the maintenance of single tones in memory is associated with activation in auditory cortex. In addition, sustained activation was observed in hippocampus and inferior frontal gyrus. Multivoxel pattern analysis showed that patterns of activity in auditory cortex and left inferior frontal gyrus distinguished the tone that was maintained in memory. Functional connectivity during maintenance was demonstrated between auditory cortex and both the hippocampus and inferior frontal cortex. The data support a system for auditory working memory based on the maintenance of sound-specific representations in auditory cortex by projections from higher-order areas, including the hippocampus and frontal cortex.In this work, we demonstrate a system for maintaining sound in working memory based on activity in auditory cortex, hippocampus, and frontal cortex, and functional connectivity among them. Specifically, our work makes three advances from the previous work. First, we robustly demonstrate hippocampal involvement in all phases of auditory working memory (encoding, maintenance, and retrieval): the role of hippocampus in working memory is controversial. Second, using a pattern classification technique, we show that activity in the auditory cortex and inferior frontal gyrus is specific to the maintained tones in working memory. Third, we show long-range connectivity of auditory cortex to hippocampus and frontal cortex, which may be responsible for keeping such representations active during working memory maintenance.

In this issue of Neuron, Albouy et al. (2017) examine the effect of TMS on oscillations in the brain during the manipulation of sounds in working memory. Low-frequency TMS to left parietal cortex increases low-frequency oscillations and improves behavior.

In this work, we show that electrophysiological responses during pitch perception are best explained by distributed activity in a hierarchy of cortical sources and, crucially, that the effective connectivity between these sources is modulated with pitch strength. Local field potentials were recorded in two subjects from primary auditory cortex and adjacent auditory cortical areas along the axis of Heschl's gyrus (HG) while they listened to stimuli of varying pitch strength. Dynamic causal modeling was used to compare system architectures that might explain the recorded activity. The data show that representation of pitch requires an interaction between nonprimary and primary auditory cortex along HG that is consistent with the principle of predictive coding.

This paper shows that current multivariate statistical monitoring technology may not detect incipient changes in the variable covariance structure nor changes in the geometry of the underlying variable decomposition. To overcome these deficiencies, the local approach is incorporated into the multivariate statistical monitoring framework to define two new univariate statistics for fault detection. Fault isolation is achieved by constructing a fault diagnosis chart which reveals changes in the covariance structure resulting from the presence of a fault. A theoretical analysis is presented and the proposed monitoring approach is exemplified using application studies involving recorded data from two complex industrial processes.

Auditory working memory (WM) is the cognitive faculty that allows us to actively hold and manipulate sounds in mind over short periods of time. We develop here a particular perspective on WM for non-verbal, auditory objects as well as for time based on the consideration of possible parallels to visual WM. In vision, there has been a vigorous debate on whether WM capacity is limited to a fixed number of items or whether it represents a limited resource that can be allocated flexibly across items. Resource allocation models predict that the precision with which an item is represented decreases as a function of total number of items maintained in WM because a limited resource is shared among stored objects. We consider here auditory work on sequentially presented objects of different pitch as well as time intervals from the perspective of dynamic resource allocation. We consider whether the working memory resource might be determined by perceptual features such as pitch or timbre, or bound objects comprising multiple features, and we speculate on brain substrates for these behavioural models. This article is part of a Special Issue entitled SI: Auditory working memory.

This paper presents an analysis of nonlinear extensions to Partial Least Squares (PLS) using error-based minimization techniques. The analysis revealed that such algorithms are maximizing the accuracy with which the response variables are predicted. Therefore, such algorithms are nonlinear reduced rank regression algorithms rather than nonlinear PLS algorithms

Partial least squares has been applied in process modelling and process performance monitoring where a large number of correlated variables are recorded. The most commonly implemented algorithm for identifying a PLS model has been the batch algorithm. In this case, data from the process is first required to be stored. In this paper an algorithm is proposed that recursively updates the parameters of PLS as and when a sample of measurements is obtained thereby reducing the need for data storage. The algorithm was tested on an artificially generated data set. The approach was then used to derive a statistic for process monitoring that was applied for the detection of faults in a continuous stirred tank reactor.

This article has been removed: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been removed at the request of the authors due to errors in the author list.

In contrast to the complex acoustic environments we encounter everyday, most studies of auditory segregation have used relatively simple signals. Here, we synthesized a new stimulus to examine the detection of coherent patterns (‘figures’) from overlapping ‘background’ signals. In a series of experiments, we demonstrate that human listeners are remarkably sensitive to the emergence of such figures and can tolerate a variety of spectral and temporal perturbations. This robust behavior is consistent with the existence of automatic auditory segregation mechanisms that are highly sensitive to correlations across frequency and time. The observed behavior cannot be explained purely on the basis of adaptation-based models used to explain the segregation of deterministic narrowband signals. We show that the present results are consistent with the predictions of a model of auditory perceptual organization based on temporal coherence. Our data thus support a role for temporal coherence as an organizational principle underlying auditory segregation. DOI: http://dx.doi.org/10.7554/eLife.00699.001, eLife digest Even when seated in the middle of a crowded restaurant, we are still able to distinguish the speech of the person sitting opposite us from the conversations of fellow diners and a host of other background noise. While we generally perform this task almost effortlessly, it is unclear how the brain solves what is in reality a complex information processing problem. In the 1970s, researchers began to address this question using stimuli consisting of simple tones. When subjects are played a sequence of alternating high and low frequency tones, they perceive them as two independent streams of sound. Similar experiments in macaque monkeys reveal that each stream activates a different area of auditory cortex, suggesting that the brain may distinguish acoustic stimuli on the basis of their frequency. However, the simple tones that are used in laboratory experiments bear little resemblance to the complex sounds we encounter in everyday life. These are often made up of multiple frequencies, and overlap—both in frequency and in time—with other sounds in the environment. Moreover, recent experiments have shown that if a subject hears two tones simultaneously, he or she perceives them as belonging to a single stream of sound even if they have different frequencies: models that assume that we distinguish stimuli from noise on the basis of frequency alone struggle to explain this observation. Now, Teki, Chait, et al. have used more complex sounds, in which frequency components of the target stimuli overlap with those of background signals, to obtain new insights into how the brain solves this problem. Subjects were extremely good at discriminating these complex target stimuli from background noise, and computational modelling confirmed that they did so via integration of both frequency and temporal information. The work of Teki, Chait, et al. thus offers the first explanation for our ability to home in on speech and other pertinent sounds, even amidst a sea of background noise. DOI: http://dx.doi.org/10.7554/eLife.00699.002

Certain sounds, for example, the squeal of chalk on a blackboard, are perceived as highly unpleasant. Functional magnetic resonance imaging (fMRI) in humans shows responses in the amygdala and auditory cortex to aversive sounds. Dynamic causal modelling (DCM) of the interaction between auditory cortex and the amygdala revealed that evoked responses to aversive sounds are relayed to the amygdala via the auditory cortex. There is a complex interaction between the -auditory cortex and amygdala involving effective connectivity in both directions. While acoustic features modulate forward connections from auditory cortex to the amygdala, the valence modulates effective connectivity from the amygdala to the auditory cortex. The results support interaction between the auditory cortex and amygdala where stimuli are first processed to a higher (object) level in the auditory cortex before assignment of valence in the amygdala.

Certain sounds, for example, the squeal of chalk on a blackboard, are perceived as highly unpleasant. Functional magnetic resonance imaging (fMRI) in humans shows responses in the amygdala and auditory cortex to aversive sounds. Dynamic causal modelling (DCM) of the interaction between auditory cortex and the amygdala revealed that evoked responses to aversive sounds are relayed to the amygdala via the auditory cortex. There is a complex interaction between the ­auditory cortex and amygdala involving effective connectivity in both directions. While acoustic features modulate forward connections from auditory cortex to the amygdala, the valence modulates effective connectivity from the amygdala to the auditory cortex. The results support interaction between the auditory cortex and amygdala where stimuli are first processed to a higher (object) level in the auditory cortex before assignment of valence in the amygdala.

This study addresses the neuronal representation of aversive sounds that are perceived as unpleasant. Functional magnetic resonance imaging in humans demonstrated responses in the amygdala and auditory cortex to aversive sounds. We show that the amygdala encodes both the acoustic features of a stimulus and its valence (perceived unpleasantness). Dynamic causal modeling of this system revealed that evoked responses to sounds are relayed to the amygdala via auditory cortex. While acoustic features modulate effective connectivity from auditory cortex to the amygdala, the valence modulates the effective connectivity from amygdala to the auditory cortex. These results support a complex (recurrent) interaction between the auditory cortex and amygdala based on object-level analysis in the auditory cortex that portends the assignment of emotional valence in amygdala that in turn influences the representation of salient information in auditory cortex.

This study used magnetoencephalography to record oscillatory activity in a group of 17 patients with chronic tinnitus. Two methods, residual inhibition and residual excitation, were used to bring about transient changes in spontaneous tinnitus intensity in order to measure dynamic tinnitus correlates in individual patients. In residual inhibition, a positive correlation was seen between tinnitus intensity and both delta/theta (6/14 patients) and gamma band (8/14 patients) oscillations in auditory cortex, suggesting an increased thalamocortical input and cortical gamma response, respectively, associated with higher tinnitus states. Conversely, 4/4 patients exhibiting residual excitation demonstrated an inverse correlation between perceived tinnitus intensity and auditory cortex gamma oscillations (with no delta/theta changes) that cannot be explained by existing models. Significant oscillatory power changes were also identified in a variety of cortical regions, most commonly midline lobar regions in the default mode network, cerebellum, insula and anterior temporal lobe. These were highly variable across patients in terms of areas and frequency bands involved, and in direction of power change. We suggest a model based on a local circuit function of cortical gamma-band oscillations as a process of mutual inhibition that might suppress abnormal cortical activity in tinnitus. The work implicates auditory cortex gamma-band oscillations as a fundamental intrinsic mechanism for attenuating phantom auditory perception.

Depth-electrode recordings from the auditory cortex of humans undergoing presurgical evaluation for epilepsy allow the recording of ensemble responses to pitch in the form of local field potentials. These recordings allow another test of the hypothesis that there is a specialized neural ensemble for pitch within auditory cortex. Moreover, the technique allows recordings from multiple sites with millisecond temporal resolution to allow modeling of the effective connectivity between these sites. Here we argue that this takes the form of a hierarchical network of pitch-sensitive regions. Activity can be understood as reflecting predictive coding, in which perceptual predictions and error messages are continuously exchanged between a higher pitch center and lower-level auditory cortex.

This work tests the relationship between auditory and phonological skill in a non-selected cohort of 238 school students (age 11) with the specific hypothesis that sound-sequence analysis would be more relevant to phonological skill than the analysis of basic, single sounds. Auditory processing was assessed across the domains of pitch, time and timbre; a combination of six standard tests of literacy and language ability was used to assess phonological skill. A significant correlation between general auditory and phonological skill was demonstrated, plus a significant, specific correlation between measures of phonological skill and the auditory analysis of short sequences in pitch and time. The data support a limited but significant link between auditory and phonological ability with a specific role for sound-sequence analysis, and provide a possible new focus for auditory training strategies to aid language development in early adolescence.