Social vocalizations are particularly important stimuli in an animal's auditory environment. Because of their importance, vocalizations should be strongly represented in auditory pathways. Mice commonly emit ultra...
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Social vocalizations are particularly important stimuli in an animal's auditory environment. Because of their importance, vocalizations should be strongly represented in auditory pathways. Mice commonly emit ultrasonic vocalizations with spectral content between 45 and 100 kHz. However, there is limited representation of these ultra-high frequencies (particularly those greater than 60 kHz) throughout the ascending auditory system. Here, we show that neurons in the inferior colliculus (IC) of mice respond strongly to conspecific vocalizations even though the energy in the vocalizations is above the neurons' frequency tuning curves. This results in an over-representation of species-specific vocalizations in the IC. In addition, neurons in mouse IC show selectivity among different vocalizations. Many vocalization-responsive neurons do not respond to the individual ultrasonic frequencies contained within the vocalizations, but they do respond to combinations of ultrasonic tones if the difference between the tones is within the excitatory frequency tuning curve. The combinations of tones that elicit responses are the quadratic and/or cubic intermodulation distortion components that are generated by the cochlea. Thus, the intermodulation distortions in the cochlea may provide a previously overlooked mechanism for auditory processing of complex stimuli such as vocalizations. The implication of these findings is that nonlinear interactions of frequencies, possibly caused by distortions in the system, may be used to enhance the sensitivity to behaviorally important stimuli. Published by Elsevier Ltd on behalf of IBRO.
作者：
Wang, XiaoqinJohns Hopkins Univ
Dept Biomed Engn Lab Auditory Neurophysiol Baltimore MD 21205 USA Tsinghua Univ
Tsinghua Lab Brain & Intelligence THBI Beijing 100084 Peoples R China Tsinghua Univ
Dept Biomed Engn Beijing 100084 Peoples R China
How the cerebral cortex encodes auditory features of biologically important sounds, including speech and music, is one of the most important questions in auditory neuroscience. The pursuit to understand related neural...
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How the cerebral cortex encodes auditory features of biologically important sounds, including speech and music, is one of the most important questions in auditory neuroscience. The pursuit to understand related neural coding mechanisms in the mammalian auditory cortex can be traced back several decades to the early exploration of the cerebral cortex. Significant progress in this field has been made in the past two decades with new technical and conceptual advances. This article reviews the progress and challenges in this area of research.
Laboratory rats, either made anosmic or subjected to sham operations, were later rendered capable of discriminative preference for NaCl over an equimolar LiCl solution. During a series of two-bottle tests (NaCl opposi...
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Laboratory rats, either made anosmic or subjected to sham operations, were later rendered capable of discriminative preference for NaCl over an equimolar LiCl solution. During a series of two-bottle tests (NaCl opposite LiCl), the importance of olfaction relative to that of taste in the discrimination was determined by such measures as initial fluid intakes, first min alternations, and first min fluid intakes. The rats proved able to distinguish by taste between the solutions, and olfactory cues were neither required nor important in the discrimination.
Aging C57BL/6 mice show a progressive decline in sensitivity to sound, beginning with high frequencies. In the inferior colliculus (IC), tonotopic organization--the orderly representation of frequency from low to high...
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Aging C57BL/6 mice show a progressive decline in sensitivity to sound, beginning with high frequencies. In the inferior colliculus (IC), tonotopic organization--the orderly representation of frequency from low to high along the dorsoventral dimension--shows marked changes. No neurons respond to high frequencies, most respond best to a restricted range of frequencies, and ventral neurons become responsive to low frequencies. These age-related response alterations have implications for hearing problems of aging humans.
The recorded responses of single neurons often vary considerably in the numbers of spikes emitted across repeats of a single experimental condition. Because of this irregularity and for theoretical convenience the res...
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The recorded responses of single neurons often vary considerably in the numbers of spikes emitted across repeats of a single experimental condition. Because of this irregularity and for theoretical convenience the responses are often approximated using a Poisson process. However, it has been frequently pointed out that many details of the responses, including the distribution of spike counts across similar trials, are not consistent with a Poisson process, even an inhomogeneous one. Wiener and Richmond (2003, J Neurosci 23:2394-2406) showed that the spike count distributions could usually be fitted nicely by mixtures of a few (1-3) Poisson distributions, a step they regarded as a computational convenience. Now, we find that a substantial proportion (47%) of the neuronal responses from anterior cingulate cortex, which we conceptualize as part of a system related to the balance between work and reward, have responses with multimodal firing rate distributions. When these distributions are modeled as mixtures of Poisson distributions, the proportions of the different Poisson distributions are related to behavioral state, and might be related to cognitive factors. This suggests that the neurons undergo behaviorally-related mode changes.
An outstanding challenge in olfactory neurobiology is to explain how glomerular networks encode information about stimulus mixtures, which are typical of natural olfactory stimuli. In the moth Manduca sexta, a species...
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An outstanding challenge in olfactory neurobiology is to explain how glomerular networks encode information about stimulus mixtures, which are typical of natural olfactory stimuli. In the moth Manduca sexta, a species-specific blend of two sex-pheromone components is required for reproductive signaling. Each component stimulates a different population of olfactory receptor cells that in turn target two identified glomeruli in the macroglomerular complex of the male's antennal lobe. Using intracellular recording and staining, we examined how responses of projection neurons innervating these glomeruli are modulated by changes in the level and ratio of the two essential components in stimulus blends. Compared to projection neurons specific for one component, projection neurons that integrated information about the blend ( received excitatory input from one component and inhibitory input from the other) showed enhanced ability to track a train of stimulus pulses. The precision of stimulus-pulse tracking was furthermore optimized at a synthetic blend ratio that mimics the physiological response to an extract of the female's pheromone gland. Optimal responsiveness of a projection neuron to repetitive stimulus pulses therefore appears to depend not only on stimulus intensity but also on the relative strength of the two opposing synaptic inputs that are integrated by macroglomerular complex projection neurons.
We present an application of the information distortion approach to neural coding. The approach allows the discovery of neural symbols and the corresponding stimulus space of a neuron or neural ensemble simultaneously...
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We present an application of the information distortion approach to neural coding. The approach allows the discovery of neural symbols and the corresponding stimulus space of a neuron or neural ensemble simultaneously and quantitatively, making few assumptions about the nature of either code or relevant features. The neural codebook is derived by quantizing sensory stimuli and neural responses into small reproduction sets, and optimizing the quantization to minimize the information distortion function. The application of this approach to the analysis of coding in sensory interneurons involved a further restriction of the space of allowed quantizers to a smaller family of parametric distributions. We show that, for some cells in this system, a significant amount of information is encoded in patterns of spikes that would not be discovered through analyses based on linear stimulus-response measures.
Regulating energy metabolism is critical to maintain homeostasis of cellular and systemic functions. In the brain, specialised centres for energy storage regulation finely communicate with the periphery and integrate ...
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Regulating energy metabolism is critical to maintain homeostasis of cellular and systemic functions. In the brain, specialised centres for energy storage regulation finely communicate with the periphery and integrate signals about internal states. As a result, the behavioural responses can be directly adjusted accordingly to the energetic demands. In the fruit fly Drosophila melanogaster, one of these regulatory centres is the mushroom bodies (MBs), a brain region involved in olfactory memory. The integration of metabolic cues by the MBs has a crucial impact on learned behaviour. In this review, we explore recent advances supporting the interplay between energy metabolism and memory establishment, as well as the instructive role of energy during the switch between memory phases.
Many cortical neurons combine the information ascending and descending the cortical hierarchy. In the classical view, this information is combined nonlinearly to give rise to a single firing-rate output, which collaps...
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Many cortical neurons combine the information ascending and descending the cortical hierarchy. In the classical view, this information is combined nonlinearly to give rise to a single firing-rate output, which collapses all input streams into one. We analyze the extent to which neurons can simultaneously represent multiple input streams by using a code that distinguishes spike timing patterns at the level of a neural ensemble. Using computational simulations constrained by experimental data, we show that cortical neurons are well suited to generate such multiplexing. Interestingly, this neural code maximizes information for short and sparse bursts, a regime consistent with in vivo recordings. Neurons can also demultiplex this information, using specific connectivity patterns. The anatomy of the adult mammalian cortex suggests that these connectivity patterns are used by the nervous system to maintain sparse bursting and optimal multiplexing. Contrary to firing-rate coding, our findings indicate that the physiology and anatomy of the cortex may be interpreted as optimizing the transmission of multiple independent signals to different targets.
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