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Shihab A Shamma - One of the best experts on this subject based on the ideXlab platform.
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laminar profile of task related plasticity in ferret Primary Auditory Cortex
Scientific Reports, 2018Co-Authors: Nikolas A Francis, Shihab A Shamma, Diego Elgueda, Bernhard Englitz, Jonathan B FritzAbstract:Rapid task-related plasticity is a neural correlate of selective attention in Primary Auditory Cortex (A1). Top-down feedback from higher-order Cortex may drive task-related plasticity in A1, characterized by enhanced neural representation of behaviorally meaningful sounds during Auditory task performance. Since intracortical connectivity is greater within A1 layers 2/3 (L2/3) than in layers 4–6 (L4–6), we hypothesized that enhanced representation of behaviorally meaningful sounds might be greater in A1 L2/3 than L4–6. To test this hypothesis and study the laminar profile of task-related plasticity, we trained 2 ferrets to detect pure tones while we recorded laminar activity across a 1.8 mm depth in A1. In each experiment we analyzed high-gamma local field potentials (LFPs) and multi-unit spiking in response to identical acoustic stimuli during both passive listening and active task performance. We found that neural responses to Auditory targets were enhanced during task performance, and target enhancement was greater in L2/3 than in L4–6. Spectrotemporal receptive fields (STRFs) computed from both high-gamma LFPs and multi-unit spiking showed similar increases in Auditory target selectivity, also greatest in L2/3. Our results suggest that activity within intracortical networks plays a key role in the underlying neural mechanisms of selective attention.
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go no go task engagement enhances population representation of target stimuli in Primary Auditory Cortex
Nature Communications, 2018Co-Authors: Sophie Bagur, Stephen V. David, Shihab A Shamma, Diego Elgueda, Jonathan B Fritz, Martin Averseng, Pingbo Yin, Yves Boubenec, Srdjan OstojicAbstract:Primary sensory cortices are classically considered to extract and represent stimulus features, while association and higher-order areas are thought to carry information about stimulus meaning. Here we show that this information can in fact be found in the neuronal population code of the Primary Auditory Cortex (A1). A1 activity was recorded in awake ferrets while they either passively listened or actively discriminated stimuli in a range of Go/No-Go paradigms, with different sounds and reinforcements. Population-level dimensionality reduction techniques reveal that task engagement induces a shift in stimulus encoding from a sensory to a behaviorally driven representation that specifically enhances the target stimulus in all paradigms. This shift partly relies on task-engagement-induced changes in spontaneous activity. Altogether, we show that A1 population activity bears strong similarities to frontal Cortex responses. These findings indicate that Primary sensory cortices implement a crucial change in the structure of population activity to extract task-relevant information during behavior.
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laminar profile of task related plasticity in ferret Primary Auditory Cortex
bioRxiv, 2018Co-Authors: Nikolas A Francis, Diego Elgueda, Bernhard Englitz, Jonathan B Fritz, Shihab A ShammaAbstract:Rapid task-related plasticity is a neural correlate of selective attention in Primary Auditory Cortex (A1). Top-down feedback from higher-order Cortex may drive task-related plasticity in A1, characterized by enhanced neural representation of behaviorally meaningful sounds during Auditory task performance. Since intracortical connectivity is greater within A1 layers 2/3 (L2/3) than in layers 4-6 (L4-6), we hypothesized that enhanced representation of behaviorally meaningful sounds might be greater in A1 L2/3 than L4-6. To test this hypothesis and study the laminar profile of task-related plasticity, we trained 2 ferrets to detect pure tones while we recorded laminar activity across a 1.8 mm depth in A1. In each experiment, we analyzed currentsource densities (CSDs), high-gamma local field potentials (LFPs), and multi-unit spiking in response to identical acoustic stimuli during both passive listening and active task performance. We found that neural responses to Auditory targets were enhanced during task performance, and target enhancement was greater in L2/3 than in L4-6. Spectrotemporal receptive fields(STRFs) computed from CSDs, high-gamma LFPs, and multi-unit spiking showed similar increases in Auditory target selectivity, also greatest in L2/3. Our results suggest that activity within intracortical networks plays a key role in shaping the underlying neural mechanisms of selective attention.
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mechanisms of noise robust representation of speech in Primary Auditory Cortex
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: Nima Mesgarani, Stephen V. David, Shihab A Shamma, Jonathan B FritzAbstract:Humans and animals can reliably perceive behaviorally relevant sounds in noisy and reverberant environments, yet the neural mechanisms behind this phenomenon are largely unknown. To understand how neural circuits represent degraded Auditory stimuli with additive and reverberant distortions, we compared single-neuron responses in ferret Primary Auditory Cortex to speech and vocalizations in four conditions: clean, additive white and pink (1/f) noise, and reverberation. Despite substantial distortion, responses of neurons to the vocalization signal remained stable, maintaining the same statistical distribution in all conditions. Stimulus spectrograms reconstructed from population responses to the distorted stimuli resembled more the original clean than the distorted signals. To explore mechanisms contributing to this robustness, we simulated neural responses using several spectrotemporal receptive field models that incorporated either a static nonlinearity or subtractive synaptic depression and multiplicative gain normalization. The static model failed to suppress the distortions. A dynamic model incorporating feed-forward synaptic depression could account for the reduction of additive noise, but only the combined model with feedback gain normalization was able to predict the effects across both additive and reverberant conditions. Thus, both mechanisms can contribute to the abilities of humans and animals to extract relevant sounds in diverse noisy environments.
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Integration over multiple timescales in Primary Auditory Cortex.
The Journal of Neuroscience, 2013Co-Authors: Stephen V. David, Shihab A ShammaAbstract:Speech and other natural vocalizations are characterized by large modulations in their sound envelope. The timing of these modulations contains critical information for discrimination of important features, such as phonemes. We studied how depression of synaptic inputs, a mechanism frequently reported in Cortex, can contribute to the encoding of envelope dynamics. Using a nonlinear stimulus-response model that accounted for synaptic depression, we predicted responses of neurons in ferret Primary Auditory Cortex (A1) to stimuli with natural temporal modulations. The depression model consistently performed better than linear and second-order models previously used to characterize A1 neurons, and it produced more biologically plausible fits. To test how synaptic depression can contribute to temporal stimulus integration, we used nonparametric maximum a posteriori decoding to compare the ability of neurons showing and not showing depression to reconstruct the stimulus envelope. Neurons showing evidence for depression reconstructed stimuli over a longer range of latencies. These findings suggest that variation in depression across the cortical population supports a rich code for representing the temporal dynamics of natural sounds.
Christoph E. Schreiner - One of the best experts on this subject based on the ideXlab platform.
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distinct core thalamocortical pathways to central and dorsal Primary Auditory Cortex
Hearing Research, 2011Co-Authors: Lee M. Miller, Christoph E. Schreiner, Heather L Read, David W Nauen, Monty A Escabi, Jeffery A WinerAbstract:The cat Primary Auditory Cortex (AI) is usually assumed to form one continuous functional region. However, the dorsal and central parts of the AI iso-frequency domain contain neurons that have distinct response properties to acoustic stimuli. In this study, we asked whether neurons projecting to dorsal versus central regions of AI originate in different parts of the medial geniculate body (MGB). Spike rate responses to variations in the sound level and frequency of pure tones were used to measure characteristic frequency (CF) and frequency resolution. These were mapped with high spatial density in order to place retrograde tracers into matching frequency regions of the central narrow-band region (cNB) and dorsal AI. Labeled neurons projecting to these two parts of AI were concentrated in the middle and rostral thirds of the MGB, respectively. There was little evidence that differences in dorsal and central AI function could be due to convergent input from cells outside the ventral division of the MGB (MGBv). Instead, inputs arising from different locations along the caudal-to-rostral dimension of MGBv represent potential sources of response differences between central and dorsal sub-regions of AI.
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columnar connectivity and laminar processing in cat Primary Auditory Cortex
PLOS ONE, 2010Co-Authors: Christoph E. Schreiner, Craig A AtencioAbstract:Author(s): Atencio, Craig A; Schreiner, Christoph E | Abstract: BackgroundRadial intra- and interlaminar connections form a basic microcircuit in Primary Auditory Cortex (AI) that extracts acoustic information and distributes it to cortical and subcortical networks. Though the structure of this microcircuit is known, we do not know how the functional connectivity between layers relates to laminar processing.Methodology/principal findingsWe studied the relationships between functional connectivity and receptive field properties in this columnar microcircuit by simultaneously recording from single neurons in cat AI in response to broadband dynamic moving ripple stimuli. We used spectrotemporal receptive fields (STRFs) to estimate the relationship between receptive field parameters and the functional connectivity between pairs of neurons. Interlaminar connectivity obtained through cross-covariance analysis reflected a consistent pattern of information flow from thalamic input layers to cortical output layers. Connection strength and STRF similarity were greatest for intralaminar neuron pairs and in supragranular layers and weaker for interlaminar projections. Interlaminar connection strength co-varied with several STRF parameters: feature selectivity, phase locking to the stimulus envelope, best temporal modulation frequency, and best spectral modulation frequency. Connectivity properties and receptive field relationships differed for vertical and horizontal connections.Conclusions/significanceThus, the mode of local processing in supragranular layers differs from that in infragranular layers. Therefore, specific connectivity patterns in the Auditory Cortex shape the flow of information and constrain how spectrotemporal processing transformations progress in the canonical columnar Auditory microcircuit.
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associative learning shapes the neural code for stimulus magnitude in Primary Auditory Cortex
Proceedings of the National Academy of Sciences of the United States of America, 2004Co-Authors: Daniel B Polley, Christoph E. Schreiner, Marc A Heiser, David T Blake, Michael M. MerzenichAbstract:Since the dawn of experimental psychology, researchers have sought an understanding of the fundamental relationship between the amplitude of sensory stimuli and the magnitudes of their perceptual representations. Contemporary theories support the view that magnitude is encoded by a linear increase in firing rate established in the Primary afferent pathways. In the present study, we have investigated sound intensity coding in the rat Primary Auditory Cortex (AI) and describe its plasticity by following paired stimulus reinforcement and instrumental conditioning paradigms. In trained animals, population-response strengths in AI became more strongly nonlinear with increasing stimulus intensity. Individual AI responses became selective to more restricted ranges of sound intensities and, as a population, represented a broader range of preferred sound levels. These experiments demonstrate that the representation of stimulus magnitude can be powerfully reshaped by associative learning processes and suggest that the code for sound intensity within AI can be derived from intensity-tuned neurons that change, rather than simply increase, their firing rates in proportion to increases in sound intensity.
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tone evoked excitatory and inhibitory synaptic conductances of Primary Auditory Cortex neurons
Journal of Neurophysiology, 2004Co-Authors: Andrew Y Y Tan, Michael M. Merzenich, Li I Zhang, Christoph E. SchreinerAbstract:In Primary Auditory Cortex (AI) neurons, tones typically evoke a brief depolarization, which can lead to spiking, followed by a long-lasting hyperpolarization. The extent to which the hyperpolarization is due to synaptic inhibition has remained unclear. Here we report in vivo whole cell voltage-clamp measurements of tone-evoked excitatory and inhibitory synaptic conductances of AI neurons of the pentobarbital-anesthetized rat. Tones evoke an increase of excitatory synaptic conductance, followed by an increase of inhibitory synaptic conductance. The synaptic conductances can account for the gross time course of the typical membrane potential response. Synaptic excitation and inhibition have the same frequency tuning. As tone intensity increases, the amplitudes of synaptic excitation and inhibition increase, and the latency of synaptic excitation decreases. Our data indicate that the interaction of synaptic excitation and inhibition shapes the time course and frequency tuning of the spike responses of AI neurons.
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reward dependent plasticity in the Primary Auditory Cortex of adult monkeys trained to discriminate temporally modulated signals
Proceedings of the National Academy of Sciences of the United States of America, 2003Co-Authors: Ralph E Beitel, Xiaoqin Wang, Christoph E. Schreiner, Steven W. Cheung, Michael M. MerzenichAbstract:Adult owl monkeys were trained to detect an increase in the envelope frequency of a sinusoidally modulated 1-kHz tone. Detection was positively correlated with the magnitude of the change in the envelope frequency. Surprisingly, neuronal responses recorded in the Primary Auditory Cortex of trained monkeys were globally suppressed by the modulated tone. However, the contrast in neuronal responsiveness to small increases versus large increases in envelope frequencies was actually enhanced in the trained animals. The results suggest behaviorally contingent inhibitory and excitatory processes that are modulated by the probability that a particular signal predicts a reward.
Michael M. Merzenich - One of the best experts on this subject based on the ideXlab platform.
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manipulation of bdnf signaling modifies the experience dependent plasticity induced by pure tone exposure during the critical period in the Primary Auditory Cortex
PLOS ONE, 2013Co-Authors: Michael M. Merzenich, Etienne De Villerssidani, Rogerio Panizzutti, Renata AnomalAbstract:Sensory experience powerfully shapes cortical sensory representations during an early developmental “critical period” of plasticity. In the rat Primary Auditory Cortex (A1), the experience-dependent plasticity is exemplified by significant, long-lasting distortions in frequency representation after mere exposure to repetitive frequencies during the second week of life. In the visual system, the normal unfolding of critical period plasticity is strongly dependent on the elaboration of brain-derived neurotrophic factor (BDNF), which promotes the establishment of inhibition. Here, we tested the hypothesis that BDNF signaling plays a role in the experience-dependent plasticity induced by pure tone exposure during the critical period in the Primary Auditory Cortex. Elvax resin implants filled with either a blocking antibody against BDNF or the BDNF protein were placed on the A1 of rat pups throughout the critical period window. These pups were then exposed to 7 kHz pure tone for 7 consecutive days and their frequency representations were mapped. BDNF blockade completely prevented the shaping of cortical tuning by experience and resulted in poor overall frequency tuning in A1. By contrast, BDNF infusion on the developing A1 amplified the effect of 7 kHz tone exposure compared to control. These results indicate that BDNF signaling participates in the experience-dependent plasticity induced by pure tone exposure during the critical period in A1.
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natural restoration of critical period plasticity in the juvenile and adult Primary Auditory Cortex
The Journal of Neuroscience, 2011Co-Authors: Xiaoming Zhou, Etienne De Villerssidani, Rogerio Panizzutti, Caroline Madeira, Michael M. MerzenichAbstract:Since its first description >40 years ago, the neurological “critical period” has been predominantly described as an early, plastic postnatal brain development stage that rather abruptly advances to an aplastic or less plastic “adult” stage. Here, we show that chronic exposure of juvenile or adult rats to moderate-level acoustic noise results in a broad reversal of maturational changes that mark the infant-to-adult progression in the Primary Auditory Cortex. In time, noise exposure reinstates critical period plasticity. Cortical changes resulting from noise exposure are again reversed to reestablish a physically and functionally normal adult Cortex, by returning animals to natural acoustic environments. These studies show that at least some of neurological changes believed to mark the transition from the infantile to the mature (adult) stage are, by their nature, reversible.
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recovery of functional and structural age related changes in the rat Primary Auditory Cortex with operant training
Proceedings of the National Academy of Sciences of the United States of America, 2010Co-Authors: Etienne De Villerssidani, Kimberly L. Simpson, Loai Alzghoul, Xiaoming Zhou, Michael M. MerzenichAbstract:Cognitive decline is a virtually universal aspect of the aging process. However, its neurophysiological basis remains poorly understood. We describe here more than 20 age-related cortical processing deficits in the Primary Auditory Cortex of aging versus young rats that appear to be strongly contributed to by altered cortical inhibition. Consistent with these changes, we recorded in old rats a decrease in parvalbumin-labeled inhibitory cortical neurons. Furthermore, old rats were slower to master a simple behavior, with learning progressions marked by more false-positive responses. We then examined the effect of intensive Auditory training on the Primary Auditory Cortex in these aged rats by using an oddball discrimination task. Following training, we found a nearly complete reversal of the majority of previously observed functional and structural cortical impairments. These findings suggest that age-related cognitive decline is a tightly regulated plastic process, and demonstrate that most of these age-related changes are, by their fundamental nature, reversible.
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Manipulating critical period closure across different sectors of the Primary Auditory Cortex
Nature neuroscience, 2008Co-Authors: Etienne De Villers-sidani, Kimberly L. Simpson, Rick C.s. Lin, Michael M. MerzenichAbstract:During early brain development and through 'adult' experience-dependent plasticity, neural circuits are shaped to represent the external world with high fidelity. When raised in a quiet environment, the rat Primary Auditory Cortex (A1) has a well-defined 'critical period', lasting several days, for its representation of sound frequency. The addition of environmental noise extends the critical period duration as a variable function of noise level. It remains unclear whether critical period closure should be regarded as a unified, externally gated event that applies for all of A1 or if it is controlled by progressive, local, activity-driven changes in this cortical area. We found that rearing rats in the presence of a spectrally limited noise band resulted in the closure of the critical period for A1 sectors representing the noise-free spectral bands, whereas the critical period appeared to remain open in noise-exposed sectors, where the Cortex was still functionally and physically immature.
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critical period window for spectral tuning defined in the Primary Auditory Cortex a1 in the rat
The Journal of Neuroscience, 2007Co-Authors: Etienne De Villerssidani, Shaowen Bao, Edward F Chang, Michael M. MerzenichAbstract:Experience-dependent plasticity during development results in the emergence of highly adapted representations of the external world in the adult brain. Previous studies have convincingly shown that the Primary Auditory Cortex (A1) of the rat possesses a postnatal period of sensory input-driven plasticity but its precise timing (onset, duration, end) has not been defined. In the present study, we examined the effects of pure-tone exposure on the Auditory Cortex of developing rat pups at different postnatal ages with a high temporal resolution. We found that pure-tone exposure resulted in profound, persistent alterations in sound representations in A1 only if the exposure occurred during a brief period extending from postnatal day 11 (P11) to P13. We also found that postnatal sound exposure in this epoch led to striking alterations in the cortical representation of sound intensity.
Jonathan B Fritz - One of the best experts on this subject based on the ideXlab platform.
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laminar profile of task related plasticity in ferret Primary Auditory Cortex
Scientific Reports, 2018Co-Authors: Nikolas A Francis, Shihab A Shamma, Diego Elgueda, Bernhard Englitz, Jonathan B FritzAbstract:Rapid task-related plasticity is a neural correlate of selective attention in Primary Auditory Cortex (A1). Top-down feedback from higher-order Cortex may drive task-related plasticity in A1, characterized by enhanced neural representation of behaviorally meaningful sounds during Auditory task performance. Since intracortical connectivity is greater within A1 layers 2/3 (L2/3) than in layers 4–6 (L4–6), we hypothesized that enhanced representation of behaviorally meaningful sounds might be greater in A1 L2/3 than L4–6. To test this hypothesis and study the laminar profile of task-related plasticity, we trained 2 ferrets to detect pure tones while we recorded laminar activity across a 1.8 mm depth in A1. In each experiment we analyzed high-gamma local field potentials (LFPs) and multi-unit spiking in response to identical acoustic stimuli during both passive listening and active task performance. We found that neural responses to Auditory targets were enhanced during task performance, and target enhancement was greater in L2/3 than in L4–6. Spectrotemporal receptive fields (STRFs) computed from both high-gamma LFPs and multi-unit spiking showed similar increases in Auditory target selectivity, also greatest in L2/3. Our results suggest that activity within intracortical networks plays a key role in the underlying neural mechanisms of selective attention.
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go no go task engagement enhances population representation of target stimuli in Primary Auditory Cortex
Nature Communications, 2018Co-Authors: Sophie Bagur, Stephen V. David, Shihab A Shamma, Diego Elgueda, Jonathan B Fritz, Martin Averseng, Pingbo Yin, Yves Boubenec, Srdjan OstojicAbstract:Primary sensory cortices are classically considered to extract and represent stimulus features, while association and higher-order areas are thought to carry information about stimulus meaning. Here we show that this information can in fact be found in the neuronal population code of the Primary Auditory Cortex (A1). A1 activity was recorded in awake ferrets while they either passively listened or actively discriminated stimuli in a range of Go/No-Go paradigms, with different sounds and reinforcements. Population-level dimensionality reduction techniques reveal that task engagement induces a shift in stimulus encoding from a sensory to a behaviorally driven representation that specifically enhances the target stimulus in all paradigms. This shift partly relies on task-engagement-induced changes in spontaneous activity. Altogether, we show that A1 population activity bears strong similarities to frontal Cortex responses. These findings indicate that Primary sensory cortices implement a crucial change in the structure of population activity to extract task-relevant information during behavior.
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laminar profile of task related plasticity in ferret Primary Auditory Cortex
bioRxiv, 2018Co-Authors: Nikolas A Francis, Diego Elgueda, Bernhard Englitz, Jonathan B Fritz, Shihab A ShammaAbstract:Rapid task-related plasticity is a neural correlate of selective attention in Primary Auditory Cortex (A1). Top-down feedback from higher-order Cortex may drive task-related plasticity in A1, characterized by enhanced neural representation of behaviorally meaningful sounds during Auditory task performance. Since intracortical connectivity is greater within A1 layers 2/3 (L2/3) than in layers 4-6 (L4-6), we hypothesized that enhanced representation of behaviorally meaningful sounds might be greater in A1 L2/3 than L4-6. To test this hypothesis and study the laminar profile of task-related plasticity, we trained 2 ferrets to detect pure tones while we recorded laminar activity across a 1.8 mm depth in A1. In each experiment, we analyzed currentsource densities (CSDs), high-gamma local field potentials (LFPs), and multi-unit spiking in response to identical acoustic stimuli during both passive listening and active task performance. We found that neural responses to Auditory targets were enhanced during task performance, and target enhancement was greater in L2/3 than in L4-6. Spectrotemporal receptive fields(STRFs) computed from CSDs, high-gamma LFPs, and multi-unit spiking showed similar increases in Auditory target selectivity, also greatest in L2/3. Our results suggest that activity within intracortical networks plays a key role in shaping the underlying neural mechanisms of selective attention.
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mechanisms of noise robust representation of speech in Primary Auditory Cortex
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: Nima Mesgarani, Stephen V. David, Shihab A Shamma, Jonathan B FritzAbstract:Humans and animals can reliably perceive behaviorally relevant sounds in noisy and reverberant environments, yet the neural mechanisms behind this phenomenon are largely unknown. To understand how neural circuits represent degraded Auditory stimuli with additive and reverberant distortions, we compared single-neuron responses in ferret Primary Auditory Cortex to speech and vocalizations in four conditions: clean, additive white and pink (1/f) noise, and reverberation. Despite substantial distortion, responses of neurons to the vocalization signal remained stable, maintaining the same statistical distribution in all conditions. Stimulus spectrograms reconstructed from population responses to the distorted stimuli resembled more the original clean than the distorted signals. To explore mechanisms contributing to this robustness, we simulated neural responses using several spectrotemporal receptive field models that incorporated either a static nonlinearity or subtractive synaptic depression and multiplicative gain normalization. The static model failed to suppress the distortions. A dynamic model incorporating feed-forward synaptic depression could account for the reduction of additive noise, but only the combined model with feedback gain normalization was able to predict the effects across both additive and reverberant conditions. Thus, both mechanisms can contribute to the abilities of humans and animals to extract relevant sounds in diverse noisy environments.
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influence of context and behavior on stimulus reconstruction from neural activity in Primary Auditory Cortex
Journal of Neurophysiology, 2009Co-Authors: Nima Mesgarani, Stephen V. David, Jonathan B Fritz, Shihab A ShammaAbstract:Population responses of cortical neurons encode considerable details about sensory stimuli, and the encoded information is likely to change with stimulus context and behavioral conditions. The details of encoding are difficult to discern across large sets of single neuron data because of the complexity of naturally occurring stimulus features and cortical receptive fields. To overcome this problem, we used the method of stimulus reconstruction to study how complex sounds are encoded in Primary Auditory Cortex (AI). This method uses a linear spectro-temporal model to map neural population responses to an estimate of the stimulus spectrogram, thereby enabling a direct comparison between the original stimulus and its reconstruction. By assessing the fidelity of such reconstructions from responses to modulated noise stimuli, we estimated the range over which AI neurons can faithfully encode spectro-temporal features. For stimuli containing statistical regularities (typical of those found in complex natural sounds), we found that knowledge of these regularities substantially improves reconstruction accuracy over reconstructions that do not take advantage of this prior knowledge. Finally, contrasting stimulus reconstructions under different behavioral states showed a novel view of the rapid changes in spectro-temporal response properties induced by attentional and motivational state.
Chloe Huetz - One of the best experts on this subject based on the ideXlab platform.
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robust neuronal discrimination in Primary Auditory Cortex despite degradations of spectro temporal acoustic details comparison between guinea pigs with normal hearing and mild age related hearing loss
Jaro-journal of The Association for Research in Otolaryngology, 2018Co-Authors: Yonane Aushana, Samira Souffi, Jeanmarc Edeline, Christian Lorenzi, Chloe HuetzAbstract:This study investigated to which extent the Primary Auditory Cortex of young normal-hearing and mild hearing-impaired aged animals is able to maintain invariant representation of critical temporal-modulation features when sounds are submitted to degradations of fine spectro-temporal acoustic details. This was achieved by recording ensemble of cortical responses to conspecific vocalizations in guinea pigs with either normal hearing or mild age-related sensorineural hearing loss. The vocalizations were degraded using a tone vocoder. The neuronal responses and their discrimination capacities (estimated by mutual information) were analyzed at single recording and population levels. For normal-hearing animals, the neuronal responses decreased as a function of the number of the vocoder frequency bands, so did their discriminative capacities at the single recording level. However, small neuronal populations were found to be robust to the degradations induced by the vocoder. Similar robustness was obtained when broadband noise was added to exacerbate further the spectro-temporal distortions produced by the vocoder. A comparable pattern of robustness to degradations in fine spectro-temporal details was found for hearing-impaired animals. However, the latter showed an overall decrease in neuronal discrimination capacities between vocalizations in noisy conditions. Consistent with previous studies, these results demonstrate that the Primary Auditory Cortex maintains robust neural representation of temporal envelope features for communication sounds under a large range of spectro-temporal degradations.