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This article is from PLoS ONE , volume 9 . Abstract Subcortical auditory nuclei were traditionally viewed as non-plastic in adulthood so that acoustic information could be stably conveyed to higher auditory areas. Studies in a variety of species, including humans, now suggest that prolonged acoustic training can drive long-lasting brainstem plasticity. The neurobiological mechanisms for such changes are not well understood in natural behavioral contexts due to a relative dearth of in vivo animal models in which to study this. Here, we demonstrate in a mouse model that a natural life experience with increased demands on the auditory system – motherhood – is associated with improved temporal processing in the subcortical auditory pathway. We measured the auditory brainstem response to test whether mothers and pup-naïve virgin mice differed in temporal responses to both broadband and tone stimuli, including ultrasonic frequencies found in mouse pup vocalizations. Mothers had shorter latencies for early ABR peaks, indicating plasticity in the auditory nerve and the cochlear nucleus. Shorter interpeak latency between waves IV and V also suggest plasticity in the inferior colliculus. Hormone manipulations revealed that these cannot be explained solely by estrogen levels experienced during pregnancy and parturition in mothers. In contrast, we found that pup-care experience, independent of pregnancy and parturition, contributes to shortening auditory brainstem response latencies. These results suggest that acoustic experience in the maternal context imparts plasticity on early auditory processing that lasts beyond pup weaning. In addition to establishing an animal model for exploring adult auditory brainstem plasticity in a neuroethological context, our results have broader implications for models of perceptual, behavioral and neural changes that arise during maternity, where subcortical sensorineural plasticity has not previously been considered.

This article is from PLoS ONE , volume 9 . Abstract Subcortical auditory nuclei were traditionally viewed as non-plastic in adulthood so that acoustic information could be stably conveyed to higher auditory areas. Studies in a variety of species, including humans, now suggest that prolonged acoustic training can drive long-lasting brainstem plasticity. The neurobiological mechanisms for such changes are not well understood in natural behavioral contexts due to a relative dearth of in vivo animal models in which to study this. Here, we demonstrate in a mouse model that a natural life experience with increased demands on the auditory system – motherhood – is associated with improved temporal processing in the subcortical auditory pathway. We measured the auditory brainstem response to test whether mothers and pup-naïve virgin mice differed in temporal responses to both broadband and tone stimuli, including ultrasonic frequencies found in mouse pup vocalizations. Mothers had shorter latencies for early ABR peaks, indicating plasticity in the auditory nerve and the cochlear nucleus. Shorter interpeak latency between waves IV and V also suggest plasticity in the inferior colliculus. Hormone manipulations revealed that these cannot be explained solely by estrogen levels experienced during pregnancy and parturition in mothers. In contrast, we found that pup-care experience, independent of pregnancy and parturition, contributes to shortening auditory brainstem response latencies. These results suggest that acoustic experience in the maternal context imparts plasticity on early auditory processing that lasts beyond pup weaning. In addition to establishing an animal model for exploring adult auditory brainstem plasticity in a neuroethological context, our results have broader implications for models of perceptual, behavioral and neural changes that arise during maternity, where subcortical sensorineural plasticity has not previously been considered.

This article is from PLoS ONE , volume 9 . Abstract Subcortical auditory nuclei were traditionally viewed as non-plastic in adulthood so that acoustic information could be stably conveyed to higher auditory areas. Studies in a variety of species, including humans, now suggest that prolonged acoustic training can drive long-lasting brainstem plasticity. The neurobiological mechanisms for such changes are not well understood in natural behavioral contexts due to a relative dearth of in vivo animal models in which to study this. Here, we demonstrate in a mouse model that a natural life experience with increased demands on the auditory system – motherhood – is associated with improved temporal processing in the subcortical auditory pathway. We measured the auditory brainstem response to test whether mothers and pup-naïve virgin mice differed in temporal responses to both broadband and tone stimuli, including ultrasonic frequencies found in mouse pup vocalizations. Mothers had shorter latencies for early ABR peaks, indicating plasticity in the auditory nerve and the cochlear nucleus. Shorter interpeak latency between waves IV and V also suggest plasticity in the inferior colliculus. Hormone manipulations revealed that these cannot be explained solely by estrogen levels experienced during pregnancy and parturition in mothers. In contrast, we found that pup-care experience, independent of pregnancy and parturition, contributes to shortening auditory brainstem response latencies. These results suggest that acoustic experience in the maternal context imparts plasticity on early auditory processing that lasts beyond pup weaning. In addition to establishing an animal model for exploring adult auditory brainstem plasticity in a neuroethological context, our results have broader implications for models of perceptual, behavioral and neural changes that arise during maternity, where subcortical sensorineural plasticity has not previously been considered.

This article is from PLoS ONE , volume 9 . Abstract Subcortical auditory nuclei were traditionally viewed as non-plastic in adulthood so that acoustic information could be stably conveyed to higher auditory areas. Studies in a variety of species, including humans, now suggest that prolonged acoustic training can drive long-lasting brainstem plasticity. The neurobiological mechanisms for such changes are not well understood in natural behavioral contexts due to a relative dearth of in vivo animal models in which to study this. Here, we demonstrate in a mouse model that a natural life experience with increased demands on the auditory system – motherhood – is associated with improved temporal processing in the subcortical auditory pathway. We measured the auditory brainstem response to test whether mothers and pup-naïve virgin mice differed in temporal responses to both broadband and tone stimuli, including ultrasonic frequencies found in mouse pup vocalizations. Mothers had shorter latencies for early ABR peaks, indicating plasticity in the auditory nerve and the cochlear nucleus. Shorter interpeak latency between waves IV and V also suggest plasticity in the inferior colliculus. Hormone manipulations revealed that these cannot be explained solely by estrogen levels experienced during pregnancy and parturition in mothers. In contrast, we found that pup-care experience, independent of pregnancy and parturition, contributes to shortening auditory brainstem response latencies. These results suggest that acoustic experience in the maternal context imparts plasticity on early auditory processing that lasts beyond pup weaning. In addition to establishing an animal model for exploring adult auditory brainstem plasticity in a neuroethological context, our results have broader implications for models of perceptual, behavioral and neural changes that arise during maternity, where subcortical sensorineural plasticity has not previously been considered.

This article is from Frontiers in Neural Circuits , volume 8 . Abstract For all neurons, a proper balance of synaptic excitation and inhibition is crucial to effect computational precision. Achievement of this balance is remarkable when one considers factors that modulate synaptic strength operate on multiple overlapping time scales and affect both pre- and postsynaptic elements. Recent studies have shown that inhibitory transmitters, glycine and GABA, are co-released in auditory nuclei involved in the computation of interaural time disparities (ITDs), a cue used to process sound source location. The co-release expressed at these synapses is heavily activity dependent, and generally occurs when input rates are high. This circuitry, in both birds and mammals, relies on inhibitory input to maintain the temporal precision necessary for ITD encoding. Studies of co-release in other brain regions suggest that GABA and glycine receptors (GlyRs) interact via cross-suppressive modulation of receptor conductance. We performed in vitro whole-cell recordings in several nuclei of the chicken brainstem auditory circuit to assess whether this cross-suppressive phenomenon was evident in the avian brainstem. We evaluated the effect of pressure-puff applied glycine on synaptically evoked inhibitory currents in nucleus magnocellularis (NM) and the superior olivary nucleus (SON). Glycine pre-application reduced the amplitude of inhibitory postsynaptic currents (IPSCs) evoked during a 100 Hz train stimulus in both nuclei. This apparent glycinergic modulation was blocked in the presence of strychnine. Further experiments showed that this modulation did not depend on postsynaptic biochemical interactions such as phosphatase activity, or direct interactions between GABA and GlyR proteins. Rather, voltage clamp experiments in which we manipulated Cl− flux during agonist application suggest that activation of one receptor will modulate the conductance of the other via local changes in Cl− ion concentration within microdomains of the postsynaptic membrane.

The purpose of the research is to gather opinions from Audiologists about whether auditory processing disorder (APD) is a unique disorder, whether they believe patients can “outgrow” APD and/or develop APD in adulthood, and how they manage patients presenting with APD-like symptoms within their department.

The purpose of the research is to gather opinions from Audiologists about whether auditory processing disorder (APD) is a unique disorder, whether they believe patients can “outgrow” APD and/or develop APD in adulthood, and how they manage patients presenting with APD-like symptoms within their department.

We investigated the response properties and functional organization of Primary Auditory Cortex (AI), to determine how the shape of the acoustic spectrum is represented in single-unit responses. The experiments employ broadband stimuli with sinusoidally modulated spectral envelopes (ripples), and systems theoretic methods to derive unit response fields and to characterize their spectro-temporal properties. These methods assume linearity of auditory responses with respect to the stimulus spectral envelope. We also address the degree of separability of response fields with respect to upward and downward moving sounds. We verified that unit responses to complex sounds with both upward and downward components can be predicted from their responses to simple ripples.

The first steps in the neural processing of sound are located in the auditory nerve and in the cochlear nuclei. To model the signal processing efficiently, we propose a simple mathematical tool that takes the minute timing of the system into account. In contrast to the situation in the cortex, the number of connections between neurons in auditory periphery is comparatively low. This gives way to an accurate modeling of the connectivity of the neuronal network. The timing is the all important feature in the peripheral neuronal auditory pathway. The primary auditory neurons e.g. phase lock to periodic sounds with important interactions with respect to both the refractory periods of the neurons and to the time delays caused by traveling times along the basilar membrane or through a synaptic connection. The mathematical tools provide a solid basis to build models for peripheral auditory processes. In particular, we study carefully a large class of refractory neurons, find analytical formulas for the spiking activity, and prove that refractory neurons respond to periodic signals by asymptotically periodic output. The methods rely on the theory of positive operators and give a numerical scheme for finding fixed points to an integral operator with geometric convergence rate. In addition, we consider a perfect integrator neuron, mathematically equivalent to randomized random walk, where the random walk is bounded from below, and solve the first passage time problem using continuous time Markov chain techniques. In an accompanying paper we set up the simulation framework as a counterpart to the present mathematical model. By suitably adjusting the few parameters in the model it is possible to reproduce the basic patterns of neural activity.

The purpose of the research is to gather opinions from Audiologists about whether auditory processing disorder (APD) is a unique disorder, whether they believe patients can “outgrow” APD and/or develop APD in adulthood, and how they manage patients presenting with APD-like symptoms within their department.

The purpose of the research is to gather opinions from Audiologists about whether auditory processing disorder (APD) is a unique disorder, whether they believe patients can “outgrow” APD and/or develop APD in adulthood, and how they manage patients presenting with APD-like symptoms within their department.

The purpose of the research is to gather opinions from Audiologists about whether auditory processing disorder (APD) is a unique disorder, whether they believe patients can “outgrow” APD and/or develop APD in adulthood, and how they manage patients presenting with APD-like symptoms within their department.

Cetaceans possess highly derived auditory systems adapted for underwater hearing. Odontocetes, or toothed whales, are thought to use specialized acoustic fats for sound reception. However, sound reception pathways in baleen whales, or mysticetes, are unknown. We investigated the auditory system of the minke whale (small mysticete species) through dissections, biomedical imaging, biochemical analyses, and sound propagation models using the Finite Element Method (FEM). We discovered a large, well-formed fat body extending from the blubber region to the ears and contacting the ossicles. The basic morphology and biochemical composition of the minke whale ear fats were very different from those of odontocete acoustic fats. However, the two tissues shared some subtle characteristics. FE models showed that the presence of the ear fats help to focus sound by the ears, which could be attributed to the low sound speed of the tissue. Sound bends towards regions of minimum sound speed, and fats are known to have lower sound speeds than other soft tissues. In an aquatic habitat where the air-filled ear canal is no longer effective, we propose that both odontocete and mysticete cetaceans have incorporated fatty tissues into their auditory systems for underwater sound reception.

Cetaceans possess highly derived auditory systems adapted for underwater hearing. Odontocetes, or toothed whales, are thought to use specialized acoustic fats for sound reception. However, sound reception pathways in baleen whales, or mysticetes, are unknown. We investigated the auditory system of the minke whale (small mysticete species) through dissections, biomedical imaging, biochemical analyses, and sound propagation models using the Finite Element Method (FEM). We discovered a large, well-formed fat body extending from the blubber region to the ears and contacting the ossicles. The basic morphology and biochemical composition of the minke whale ear fats were very different from those of odontocete acoustic fats. However, the two tissues shared some subtle characteristics. FE models showed that the presence of the ear fats help to focus sound by the ears, which could be attributed to the low sound speed of the tissue. Sound bends towards regions of minimum sound speed, and fats are known to have lower sound speeds than other soft tissues. In an aquatic habitat where the air-filled ear canal is no longer effective, we propose that both odontocete and mysticete cetaceans have incorporated fatty tissues into their auditory systems for underwater sound reception.

A common complaint of listeners with normal clinical hearing thresholds is difficulty in understanding speech in noise. Recent animal studies have shown that noise exposure causes selective loss of low spontaneous rate auditory nerve fibers (ANFs) and reduction of auditory brainstem response wave-I amplitudes. The goal of this research is to utilize computational models of the auditory periphery and auditory cortex to study the effect of low spontaneous rate ANF loss on the cortical representation of speech intelligibility in noise. The auditory-periphery model of Zilany et al. (JASA 2009,2014) is used to make predictions of auditory nerve (AN) responses to speech stimuli under a variety of difficult listening conditions. The resulting cochlear neurogram, a spectrogram-like output based on ANF outputs, is then used as a low-auditory-level foundation for two different but related cortical representations of speech: the Spectro-Temporal Modulation Index (STMI; Elihali et al., Speech Comm. 2003) and 2D Fourier Analysis (Wang and Quatieri., IEEE, 2012). Reducing the number of low spontaneous rate ANFs in the cochlear neurogram was found to cause a blurring of speaker specific components that increase the difficulty of speaker separation. Suprathreshold deficits in speech intelligibility, as measured by STMI, may be related to ANF loss or degradation. Further study may lead to strategies to mitigate intelligibility decline by optimizing information at the cortical level.

Predictive coding is a leading theoretical framework for understanding sensory processing as statistical inference. Its main tenet is that sensory input is analysed by prediction error units: neural processors that test our internal expectations on the sensory world against the sensory input. Prediction error units encode the difference between the expectations and the actual input. This difference, known as prediction error, is transmitted upstream to higher levels of the processing hierarchy, and used to inform updates in our internal beliefs. The encoding of positive prediction error, signals that aim to add unaccounted elements to the internal representations, has been extensively studied before both in sensory cortices and the subcortical sensory pathways. Whether sensory pathways also encode negative prediction error, signals that aim to remove representations of expected percepts that were absent in the sensory input, has not been unambiguously considered before. Here we will use human fMRI to measure responses to omissions of sounds for which participants held varying levels of expectations. We will use modelling and Bayesian model comparison to compute the posterior probability that neural populations of auditory cortex, auditory midbrain, and auditory thalamus specifically encode negative prediction error. Since the study will be conducted with a very high statistical power (1-beta > 0.9 at the single-subject level; 15 biological replications), results will provide conclusive evidence in favour or against the hypotheses that negative prediction error in encoded at each of the three stations of the auditory pathway.