Auditory Signal Processing Research Articles

Resilience of the endangered sperm whale Physeter macrocephalus to foraging disturbance in the Gulf of Mexico, USA: a bioenergetic approach

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 589:241-261 (2018) - DOI: https://doi.org/10.3354/meps12457 Resilience of the endangered sperm whale Physeter macrocephalus to foraging disturbance in the Gulf of Mexico, USA: a bioenergetic approach Nicholas A. Farmer1,*, Dawn P. Noren2, Erin M. Fougères1, Abigail Machernis3, Kyle Baker4 1NOAA/National Marine Fisheries Service, Southeast Regional Office, 263 13th Ave S., St. Petersburg, Florida 33701, USA 2Conservation Biology Division, Northwest Fisheries Science Center, National Marine Fisheries Service, NOAA, 2725 Montlake Boulevard East, Seattle, Washington 98112, USA 3JPS, Inc., under contract to NOAA/National Marine Fisheries Service, Southeast Regional Office, 263 13th Ave S, St. Petersburg, Florida 33701, USA 4Bureau of Ocean Energy Management’s Office of Renewable Energy Programs, Mail Stop VAM-OREP, 45600 Woodland Road, Sterling, Virginia 20166, USA *Corresponding author: nick.farmer@noaa.gov ABSTRACT: The endangered sperm whale Physeter macrocephalus spends the majority of its time foraging, relying upon echolocation to locate and consume several 100 kg of prey per day. In the northern Gulf of Mexico, sperm whales are exposed to a variety of anthropogenic stressors, including ship strikes, fisheries interactions, habitat loss and degradation due to oil and gas development, and chemical and noise pollution. In particular, they are exposed to high levels of anthropogenic noises related to geological and geophysical surveys for hydrocarbon deposits. The sounds produced by these surveys could reduce sensory volume, increase search effort required to locate resources, and interfere with auditory signal processing critical to foraging success. We developed a stochastic life-stage structured bioenergetic model to evaluate the consequences of reduced foraging efficiency on carbohydrate, lipid, and protein reserves in the blubber, muscle, and viscera. The model indicates that individual resilience to foraging disruptions is primarily a function of size (i.e. reserve capacity) and daily energetic demands. Mothers are the most vulnerable life stage due to the high energy demands associated with pregnancy and lactation. Continuous disruption has a greater impact than intermittent disruption; even minor foraging disruptions may lead to terminal starvation if the whales have no opportunity to replenish reduced reserves. Infrequent, minor disruptions in foraging are unlikely to be fatal, but may result in reduced body reserves that may be associated with reduced reproductive success. Our model provides a bioenergetic framework for evaluating the level, frequency, and consequences of foraging disruptions associated with anthropogenic stressors. KEY WORDS: Conservation · Disturbance · Foraging ecology · Risk assessment · Odontocete Full text in pdf format PreviousNextCite this article as: Farmer NA, Noren DP, Fougères EM, Machernis A, Baker K (2018) Resilience of the endangered sperm whale Physeter macrocephalus to foraging disturbance in the Gulf of Mexico, USA: a bioenergetic approach. Mar Ecol Prog Ser 589:241-261. https://doi.org/10.3354/meps12457 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 589. Online publication date: February 23, 2018 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2018 Inter-Research.

Multichannel cochlear implant for selective neuronal activation and chronic use in the free-moving Mongolian gerbil

BackgroundAnimal models for chronic multichannel cochlear implant stimulation and selective neuronal activation contribute to a better understanding of auditory signal processing and central neural plasticity. New methodThis paper describes the design and surgical implantation of a multichannel cochlear implant (CI) system for chronic use in the free-moving gerbil. For chronic stimulation, adult-deafened gerbils were connected to a multichannel commutator that allowed low resistance cable rotation and stable electric connectivity to the current source. ResultsDespite the small scale of the gerbil cochlea and auditory brain regions, final electrophysiological mapping experiments revealed selective and tonotopically organized neuronal activation in the auditory cortex. Contact impedances and electrically evoked auditory brainstem responses were stable over several weeks demonstrating the long-term integrity of the implant and the efficacy of the stimulation. Comparison with existing methodsMost animal models on multichannel signal processing and stimulation-induced plasticity are limited to larger animals such as ferrets, cats and primates. Multichannel CI stimulation in the free-moving rodent and evidence for selective neuronal activation in gerbil auditory cortex have not been previously reported. ConclusionsOverall, our results show that the gerbil is a robust rodent model for selective and tonotopically organized multichannel CI stimulation. We anticipate that this model provides a useful tool to develop and test both passive stimulation and behavioral training strategies for plastic reorganization and restoration of degraded unilateral and bilateral central auditory signal processing in the hearing impaired and deaf central auditory system.

Attenuation of visual reafferent signals in the parietal cortex during voluntary movement.

It is well established that the cortical processing of somatosensory and auditory signals is attenuated when they result from self-generated actions compared with external events. This phenomenon is thought to result from an efference copy of motor commands used to predict the sensory consequences of an action through a forward model. The present work examined whether attenuation also takes place for visual reafferent signals from the moving limb during voluntary reaching movements. To address this issue, EEG activity was recorded in a condition in which visual feedback of the hand was provided in real time and compared with a condition in which it was presented with a 150-ms delay, thus creating a mismatch between the predicted and actual visual consequences of the movement. Results revealed that the amplitude of the N1 component of the visual event-related potential evoked by hand visual feedback over the parietal cortex was significantly smaller when presented in real time compared with when it was delayed. These data suggest that the cortical processing of visual reafferent signals is attenuated when they are correctly predicted, likely as a result of a forward model.

Detection of Excitatory and Inhibitory Synapses in the Auditory System Using Fluorescence Immunohistochemistry and High-Resolution Fluorescence Microscopy.

In sensory systems, a balanced excitatory and inhibitory circuit along the ascending pathway is not only important for the establishment of topographically ordered connections from the periphery to the cortex but also for temporal precision of signal processing. The accomplishment of spatial and temporal cortical resolution in the central nervous system is a process that is likely initiated by the first sensory experiences that drive a period of increased intracortical inhibition. In the auditory system, the time of first sensory experience is also the period in which a reorganization of cochlear efferent and afferent fibers occurs leading to the mature innervation of inner and outer hair cells. This mature hair cell innervation is the basis of accurate sound processing along the ascending pathway up to the auditory cortex. We describe here, a protocol for detecting excitatory and inhibitory marker proteins along the ascending auditory pathway, which could be a useful tool for detecting changes in auditory signal processing during various forms of hearing disorders. Our protocol uses fluorescence immunohistochemistry in combination with high-resolution fluorescence microscopy in cochlear and brain tissue.

Signal Processing in Periodically Forced Gradient Frequency Neural Networks.

Oscillatory instability at the Hopf bifurcation is a dynamical phenomenon that has been suggested to characterize active non-linear processes observed in the auditory system. Networks of oscillators poised near Hopf bifurcation points and tuned to tonotopically distributed frequencies have been used as models of auditory processing at various levels, but systematic investigation of the dynamical properties of such oscillatory networks is still lacking. Here we provide a dynamical systems analysis of a canonical model for gradient frequency neural networks driven by a periodic signal. We use linear stability analysis to identify various driven behaviors of canonical oscillators for all possible ranges of model and forcing parameters. The analysis shows that canonical oscillators exhibit qualitatively different sets of driven states and transitions for different regimes of model parameters. We classify the parameter regimes into four main categories based on their distinct signal processing capabilities. This analysis will lead to deeper understanding of the diverse behaviors of neural systems under periodic forcing and can inform the design of oscillatory network models of auditory signal processing.

Hearing in Insects.

Insect hearing has independently evolved multiple times in the context of intraspecific communication and predator detection by transforming proprioceptive organs into ears. Research over the past decade, ranging from the biophysics of sound reception to molecular aspects of auditory transduction to the neuronal mechanisms of auditory signal processing, has greatly advanced our understanding of how insects hear. Apart from evolutionary innovations that seem unique to insect hearing, parallels between insect and vertebrate auditory systems have been uncovered, and the auditory sensory cells of insects and vertebrates turned out to be evolutionarily related. This review summarizes our current understanding of insect hearing. It also discusses recent advances in insect auditory research, which have put forward insect auditory systems for studying biological aspects that extend beyond hearing, such as cilium function, neuronal signal computation, and sensory system evolution.

Phase synchronization in the cochlea at transition from mechanical waves to electrical spikes.

Measured auditory nervous spikes often show synchronization, phase-locking, or entrainment (P. Cariani, Neural Plast. 6(4), 142-172 (1999) and Kumaresana et al., J. Acoust. Soc. Am. 133(6), 4290-4310 (2013). Physiologically synchronization is found in the anteroventral cochlear nucleus (Joris et al., J. Neurophysiol. 71(3), 1022-1036 (1994)) or in the trapezoid body also between critical bandwidths (Louage et al., Auditory Signal Processing: Physiology, Psychoacoustics, and Models (Springer, New York, 2004), pp. 100-106). The effect is an enhancement of pitch detection, spatial localization, or speech intelligibility. To investigate the presence of synchronization already in the cochlea, in the present paper, a finite-difference time-domain model of the cochlea is implemented with conditions for spike excitation caused by mechanical basilar membrane displacement. This model shows synchronization already in the cochlea at the transition from mechanical waves to nerve spike excitation. Using a sound as model input consisting of ten harmonic overtones with random phase relations, the output spikes are strongly phase aligned after this transition. When using a two-sinusoidal complex as input, and altering the phase relations between the two sinusoidals, the output spikes show the higher sinusoidal shifting the phase of the lower one in its direction in a systematic way. Therefore, already during the transition from mechanical to electrical excitation within the cochlea, synchronization appears to be improving perception of pitch, speech, or localization.

Can current room-acoustics indices specify the quality of aural experience in concert halls?

It is a dream of acousticians to identify indices that can be used to specify the quality of aural experience in concert halls but can nevertheless be measured with physical instruments. A battery of such indices has been standardized by the International Organization for Standardization, ISO (ISO3382-1, 2013, 2009), particularly concerning the role of the hall in the quality-formation process. Yet, even considering improvements as proposed in the meantime, for example, by Bradley (2010), these and related indices are derived from physical data and not from perceptual ones, namely, perceptual properties of aural objects and scenes. Consequently, they disregard interindividual perceptual differences. To analyze the problem, one should take the perspective of concert goers, sitting in a hall and listening to a musical performance. There is no doubt that the listeners do not care about any physics-based indices in this situation. They judge on what they actually perceive: that is, on what they hear and see, on vibrations they may feel, and maybe also on smells that they sense. This conglomerate of percepts is set in relation to their expectations, namely, to internal references that are not directly accessible to external observers (Raake & Blauert, 2013; Raake & Egger, 2014). The extent to which these expectations are met will then determine their quality judgment (Jekosch, 2005a). The internal references are individual and depend, among other things, on the actual music played and the knowledge and experience that the listeners have with the particular kind of music. It has, however, to be stressed at this point that only experienced listeners are able to judge separately on the contribution of the hall to the overall quality of aural experience in it.Without doubt, various physics-based indices show significant correlation with perceptual features; for example, the reverberation time is related to reverberance and the lateral-energy fraction to the spatial extents of aural objects. Yet, all of these suffer from the fact that they abstract from concrete individual observations and thus disregard individual perceptual particulars. Further, the correlation of such indices with the corresponding aural features is limited in principle. Ergo, there is a problem of validity when it comes to the prediction of quality-of-aural-experience judgments in general and, even more so, judgments by individual listeners.In an attempt to increase the amount of correlation of the results of physical measurements with aural features, algorithms have been designed that mimic elements of peripheral auditory signal processing. Yet, although this may increase the correlation between acoustics and aural perception, these algorithms do not directly measure perceptual features. At best, they provide estimates of (primitive) perceptual attributes such as loudness, roughness, or source direction. These estimates incorporate some understanding of the peripheral auditory system but still suffer from the disadvantage of abstracting from individual listeners. Thus, although the validity problem has been reduced, it still persists.It goes without saying that sound quality is an important component of aural experience in performance spaces. As mentioned above, quality judgments require internal reference of the listeners. To get access to these references by external observation is very tedious, as they are concepts in the listeners' minds. As a consequence, developing models that functionally mimic human quality formation is a complex task. Hence, respective more sophisticated instrumental approaches to sound-quality assessment, as, for example, ITU-PEAQ (a standardized algorithm for assessing soundquality degradation due to transmission [e.g., Rumsey, 2010; Thiede et al., 2000]), do not incorporate internal references. In fact, algorithms like this still abstract from individuality. Consequently, they also do not really measure perceptual quality but only provide generalized estimates of it. …

Relating physiology to perception: The case of the notched-noise masker

Sharpness of peripheral tuning is an essential factor in auditory signal processing. The notched-noise (NN) masking paradigm (Patterson, 1976, JASA) is an ingenious strategy used in numerous studies to estimate peripheral tuning bandwidths, filter shapes, and level-dependence in normal and impaired ears. Interpretation of NN results is based on the power-spectrum model of masking; however, the fact that NN thresholds are little influenced by a roving-level paradigm calls this interpretation into question (Lentz et al., 1999, JASA). Here, we explore neural cues for detection in NN in auditory-nerve (AN) and midbrain (inferior colliculus, IC) responses. Strong low-frequency fluctuations in AN discharge patterns associated with sharp spectral edges provide effective inputs for midbrain neurons tuned to low-frequency fluctuations. Addition of a tone target reduces the fluctuations in some frequency channels, creating a strong contrast in the fluctuation profile along the frequency axis. We explore the NN paradigm using computational models for AN and amplitude-modulation (AM) tuned IC neurons. Recordings from band-pass AM tuned neurons in the IC of awake rabbit support the hypothesis that the midbrain response profile can explain perception in the NN paradigm. Interpretation of NN masking results should include not only peripheral tuning but also central processing mechanisms.

When auditory and visual signal processing conflict: cross-modal interference in extended work periods

Auditory and visual stimuli presented at intervals of about 300 m sec often produce miss errors in one or the other channel, which result from a bottleneck in a neural circuit associated with executive memory. The present study examined the possibility that cross-modal interference could carry over to performance units that transpire over 3 min or longer. An N-back task performed by 113 undergraduates with simultaneous auditory and visual stimuli was organised into 1-min blocks of 20 trials in 2-back and 3-back conditions. Results showed that impairment of visual processing was more frequent than impairment of auditory processing under conditions of fatigue. A substantial number of person blocks showed no such interference, however. Bottlenecks during early stages of processing may have more extensive effects on later processing than previously recognised. Further research should consider perceptual cycling in longer term tasks involving complex stimuli.

TRPC1 and metabotropic glutamate receptor expression in rat auditory midbrain neurons.

Canonical transient receptor potential (TRPC) channels are plasma membrane cation channels included in the TRP superfamily. TRPC1 is expressed widely in the central nervous system and is linked to group I metabotropic glutamate receptors (mGluRs). In the auditory brainstem, TRPC1 expression has never been described, although group I mGluRs are present. In the central nucleus of the inferior colliculus (CIC), activation of group I mGluRs induces an extracellular Ca(2+) influx after store depletion. Therefore, this study examines whether TRPC1 is expressed in this region to establish a correlation with mGluRs. By quantitative reverse transcription-polymerase chain reaction and Western blotting, this study assesses the presence of TRPC1 along with both group I mGluR subtypes mGluR1 and mGluR5 in the rat inferior colliculus (IC). All these molecules present a robust expression in the IC. By confocal double immunofluorescence, this study also demonstrates that TRPC1 colocalizes with parvalbumin, a CIC neuronal marker, in many cells. Conversely, TRPC1 was lacking in glial fibrillary acidic protein-positive glial cells. All the glutamate acid decarboxylase 67 (GAD67)-immunoreactive neurons and many GAD67-negative neurons were positive to TRPC1, which indicates the presence of TRPC1 in γ-aminobutyric acid (GABA)-ergic and non-GABAeregic neurons. With regard to subcellular distribution, TRPC1 was absent in synaptophysin-immunoreactive axonic terminals but colocalized with postsynaptic marker microtubule-associated protein 2 in cell bodies and dendrites. TRPC1 totally overlapped group I mGluRs, which supports the involvement of TRPC1 in the mGluR pathway and, likely, in auditory signal processing at the midbrain level. .

Autocorrelation-Based Features for Speech Representation

This study investigates autocorrelation-based features as a potential basis for phonetic and syllabic distinctions. The work comes out of a theory of auditory signal processing based on central monaural autocorrelation and binaural crosscorrelation representations. Correlation-based features are used to predict monaural and binaural perceptual attributes that are important for the architectural acoustic design of concert halls: pitch, timbre, loudness, duration, reverberation-related coloration, sound direction, apparent source width, and envelopment (Ando, 1985, 1998; Ando and Cariani, 2009). The current study investigates the use of features of monaural autocorrelation functions (ACFs) for representing phonetic elements (vowels), syllables (CV pairs), and phrases using a small set of temporal factors extracted from the short-term running ACF. These factors include listening level (loudness), zero-lag ACF peak width (spectral tilt), τ1 (voice pitch period), φ1 (voice pitch strength), τe (effective duration of the ACF envelope, temporal repetitive continuity/contrast), segment duration, and Δφ1/Δt (the rate of pitch strength change, related to voice pitch attack-decay dynamics). Times at which ACF effective duration τe is minimal reflect rapid signal pattern changes that usefully demarcate segmental boundaries. Results suggest that vowels, CV syllables, and phrases can be distinguished on the basis of this ACF-derived feature set.

Synaptic mechanisms for generating temporal diversity of auditory representation in the dorsal cochlear nucleus.

In central auditory pathways, neurons exhibit a great diversity of temporal discharge patterns, which may contribute to the parallel processing of auditory signals. How such response diversity emerges in the central auditory circuits remains unclear. Here, we investigated whether synaptic mechanisms can contribute to the generation of the temporal response diversity at the first stage along the central auditory neuraxis. By in vivo whole-cell voltage-clamp recording in the dorsal cochlear nucleus of rats, we revealed excitatory and inhibitory synaptic inputs underlying three different firing patterns of fusiform/pyramidal neurons in response to auditory stimuli: "primary-like," "pauser," and "buildup" patterns. We found that primary-like neurons received strong, fast-rising excitation, whereas pauser and buildup neurons received accumulating excitation with a relatively weak fast-rising phase, followed by a slow-rising phase. Pauser neurons received stronger fast-rising excitation than buildup cells. On the other hand, inhibitory inputs to the three types of cells exhibited similar temporal patterns, all with a strong fast-rising phase. Dynamic-clamp recordings demonstrated that the differential temporal patterns of excitation could primarily account for the different discharge patterns. In addition, discharge pattern in a single neuron varied in a stimulus-dependent manner, which could be attributed to the modulation of excitation/inhibition balance by different stimuli. Further examination of excitatory inputs to vertical/tuberculoventral and cartwheel cells suggested that fast-rising and accumulating excitation might be conveyed by auditory nerve and parallel fibers, respectively. A differential summation of excitatory inputs from the two sources may thus contribute to the generation of response diversity.

Development and modulation of intrinsic membrane properties control the temporal precision of auditory brain stem neurons.

Passive and active membrane properties determine the voltage responses of neurons. Within the auditory brain stem, refinements in these intrinsic properties during late postnatal development usually generate short integration times and precise action-potential generation. This developmentally acquired temporal precision is crucial for auditory signal processing. How the interactions of these intrinsic properties develop in concert to enable auditory neurons to transfer information with high temporal precision has not yet been elucidated in detail. Here, we show how the developmental interaction of intrinsic membrane parameters generates high firing precision. We performed in vitro recordings from neurons of postnatal days 9-28 in the ventral nucleus of the lateral lemniscus of Mongolian gerbils, an auditory brain stem structure that converts excitatory to inhibitory information with high temporal precision. During this developmental period, the input resistance and capacitance decrease, and action potentials acquire faster kinetics and enhanced precision. Depending on the stimulation time course, the input resistance and capacitance contribute differentially to action-potential thresholds. The decrease in input resistance, however, is sufficient to explain the enhanced action-potential precision. Alterations in passive membrane properties also interact with a developmental change in potassium currents to generate the emergence of the mature firing pattern, characteristic of coincidence-detector neurons. Cholinergic receptor-mediated depolarizations further modulate this intrinsic excitability profile by eliciting changes in the threshold and firing pattern, irrespective of the developmental stage. Thus our findings reveal how intrinsic membrane properties interact developmentally to promote temporally precise information processing.

Sound effects with AUditory syntaX—A high-level scripting language for sound processing

AUditory syntaX (AUX) is a high-level scripting programming language specifically crafted for the generation and processing of auditory signals (Kwon, 2012; Behav Rev 44, 361–373). AUX does not require knowledge or prior experience in computer programming. Rather, AUX provides an intuitive and descriptive environment where users focus on perceptual components of the sound, without tedious tasks unrelated to the perception such as memory management or array handling often required in other computer languages such as C + + or MATLAB that are popularly used in auditory science. This presentation provides a demonstration of AUX for the generation and processing of various sound effects, particularly “fun” or “spooky” sounds. Processing methods for sound effects widely used in arts, films and other media, such as reverberation, echoes, modulation, pitch shift, and flanger/phaser, will be reviewed and coding in AUX to generate those effects and the generated sounds will be demonstrated.

Advanced Binaural Sound Localization in 3-D for Humanoid Robots

One of the key features of the human auditory system is its nearly constant omnidirectional sensitivity, e.g., the system reacts to alerting signals coming from a direction away from the sight of focused visual attention. Auditory signal processing already starts outside the head. The external sound field has to couple into the ear canals. The relative positions of the two ear canals and the sound source lead to a coupling that is strongly dependent on frequency. In this context, not only the two pinnae, but also the whole head have an important functional role, which is best described as a spatial filtering process. This linear filtering is usually quantified in terms of so-called head-related transfer functions (HRTFs), which can also be interpreted as the directivity characteristics of the two ears. In this paper, the HRTF constitutes the cornerstone of a sound localization algorithm, which uses Bayesian information fusion to increase the localization resolution in a 3-D reverberant environment. The localization performance is demonstrated through simulation and is further tested in a household environment. Compared with the existing techniques, the method is able to localize, with higher accuracy, 3-D sound sources under high reverberation conditions. The simplicity of the presented algorithm allows a cost-effective real-time implementation for robotic platforms.

The relationship between speaker size perception and the auditory filter

When we hear a new voice on the radio, we can tell whether the speaker is an adult or a child. We can also extract the message of the communication without being confused by the size information. This shows that auditory signal processing is scale invariant, automatically segregating information about vocal tract shape from information about vocal tract length. Patterson and colleagues have performed a series of experiments to measure the characteristics of size/shape perception [e.g., Smith et al., J. Acoust. Soc. Am. 117(1), 305–318 (2005)], and provided a mathematical basis for auditory scale invariance in the form of the stabilized wavelet-Mellin transform (SWMT) [Irino and Patterson, Speech Commun. 36(3–4), 181–203 (2002)]. The mathematics of the SWMT dictates the optimal form of the auditory filter, insofar as it must satisfy minimal uncertainty in a time-scale representation [Irino and Patterson, J. Acoust. Soc. Am. 101(1), 412–419 (1997)]. The resulting gammachirp auditory filter is an asymmetric extension of the earlier gammatone auditory filter—one which can explain the level dependence of notched-noise masking. Thus, although it is not immediately intuitive, speaker size perception and auditory filter shape are both aspects of a larger, unified framework for auditory signal processing.

The relationship between verbal and nonverbal auditory signal processing in conduction aphasia: behavioral and anatomical evidence for common decoding mechanisms

The processing of nonverbal auditory stimuli has not yet been sufficiently investigated in patients with aphasia. On the basis of a duration discrimination task, we examined whether patients with left-sided cerebrovascular lesions were able to perceive time differences in the scale of approximately 150 ms. Further linguistic and memory-related tasks were used to characterize more exactly the relationships in the performances between auditory nonverbal task and selective linguistic or mnemonic disturbances. All examined conduction aphasics showed increased thresholds in the duration discrimination task. The low thresholds on this task were in a strong correlative relation to the reduced performances in repetition and working memory task. This was interpreted as an indication of a pronounced disturbance in integrating auditory verbal information into a long-term window (sampling disturbance) resulting in an additional load of working memory. In order to determine the lesion topography of patients with sampling disturbances, the anatomical and psychophysical data were correlated on the basis of a voxelwise statistical approach. It was found that tissue damage extending through the insula, the posterior superior temporal gyrus, and the supramarginal gyrus causes impairments in sequencing of time-sensitive information.

Toward a vestibular contribution to social cognition

Social cognition encompasses perception of self and others as well as self-other interactions. Self-other interactions rely on a wide range of cognitive processes such as memory, language, reasoning, and emotion processing (Beer and Ochsner, 2006). Within the last few years, one productive line of research in social neuroscience has investigated the multisensory and motor foundations of self-other interactions, including emotion perception, emotional contagion, empathy, self-other distinction, or self-other knowledge (e.g., Singer et al., 2004; Iacoboni et al., 2005; Ambrosini et al., 2013; Manera et al., 2013). While a strong emphasis has been traditionally put on visual processes, recent research has noted that self-other distinction and mirroring also require processing of auditory (e.g., self-other voice recognition), proprioceptive, and interoceptive signals (Damasio, 2000; Schutz-Bosbach et al., 2006; Tsakiris et al., 2011; Seth, 2013; Xu et al., 2013). In spite of this multisensory development, a vestibular contribution to the embodied mechanisms of social interactions has until now been largely overlooked. This is surprising as the vestibular system has been involved in a growing number of cognitive functions (Smith et al., 2005; Miller and Ngo, 2007; Gurvich et al., 2013), in addition to its crucial role in distinguishing self- and non-self motion. The claim of the present opinion article is that vestibular information should not be ignored when investigating the sensorimotor foundations of social cognition. We present several lines of evidence indicating that vestibular signals may be involved in the sensory bases of self-other distinction and mirroring, emotion perception and perspective taking.

Mode-locking neurodynamics predict human auditory brainstem responses to musical intervals

The auditory nervous system is highly nonlinear. Some nonlinear responses arise through active processes in the cochlea, while others may arise in neural populations of the cochlear nucleus, inferior colliculus and higher auditory areas. In humans, auditory brainstem recordings reveal nonlinear population responses to combinations of pure tones, and to musical intervals composed of complex tones. Yet the biophysical origin of central auditory nonlinearities, their signal processing properties, and their relationship to auditory perception remain largely unknown. Both stimulus components and nonlinear resonances are well represented in auditory brainstem nuclei due to neural phase-locking. Recently mode-locking, a generalization of phase-locking that implies an intrinsically nonlinear processing of sound, has been observed in mammalian auditory brainstem nuclei. Here we show that a canonical model of mode-locked neural oscillation predicts the complex nonlinear population responses to musical intervals that have been observed in the human brainstem. The model makes predictions about auditory signal processing and perception that are different from traditional delay-based models, and may provide insight into the nature of auditory population responses. We anticipate that the application of dynamical systems analysis will provide the starting point for generic models of auditory population dynamics, and lead to a deeper understanding of nonlinear auditory signal processing possibly arising in excitatory-inhibitory networks of the central auditory nervous system. This approach has the potential to link neural dynamics with the perception of pitch, music, and speech, and lead to dynamical models of auditory system development.This article is part of a Special Issue entitled <Music: A window into the hearing brain>.