Experience Dependent Changes in the Auditory Cortical Representation of Natural Sounds PDF Download

Author: Frank Lin
Publisher:
ISBN:
Category : Auditory cortex
Languages : en
Pages :

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Book Description
Vocal communication sounds are an important class of signals due to their role in social interaction, reproduction, and survival. The higher-order mechanisms by which our auditory system detects and discriminates these sounds to generate perception is still poorly understood. The auditory cortex is thought to play an important role in this process, and our current work provides new evidence that the auditory cortex changes its neural representation of sounds that are acquired in natural social contexts. We use a mouse ultrasonic communication system between pups and adult females to elucidate this. We record single neurons in the auditory cortex of awake mice, and assess the cortical differences between animals that either do (mothers) or do not (naïve virgins) recognize the pup ultrasounds as behaviorally relevant. We then evaluate the role that pup experience and the maternal physiological state play in this cortical plasticity. Finally, we develop a model to predict the responses to pup vocalizations as a way to segregate the diversity of cortical neuronal responses in the hope of more clearly assessing their roles in processing acoustic features. Our results demonstrate the detailed nature by which the core auditory cortex processes natural vocalizations, showing how it changes to represent behavioral relevance.

Author: Michele Nerissa Insanally
Publisher:
ISBN:
Category :
Languages : en
Pages : 84

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Development of complex sound representations in the primary auditory cortex by Michele Nerissa Insanally Doctor of Philosophy in Neuroscience University of California, Berkeley Professor Shaowen Bao, PhD., Chair The brain has a tremendous ability to change as a result of experience; this property is known as plasticity. Our mastery of soccer, rhetoric, agriculture and instrumentation are all learned skills that require experience. While the brain is plastic throughout life, during early development, the brain demonstrates a heightened sensitivity to experience. This unique epoch during development in which the brain is particularly susceptible to change is called a critical period. During the critical period, sensory experience results in significant modifications in structure and function. The set of studies described in this dissertation aim to investigate how complex sound representation develops during the critical period in the rat primary auditory cortex. Previous examinations of the critical period in the auditory cortex have typically used simple tonal stimuli. Repeated exposure of rat pups to a tone, for instance, has been shown to selectively enlarge cortical representation of the tone and alter perceptual behaviors. However, probing cortical plasticity with a single-frequency tone might not reveal the full complexity and dynamics of critical period plasticity. After all, natural, biologically important sounds are generally complex with respect to their spectrotemporal properties. Natural sounds often have frequencies that vary in time and amplitude modulation. Psychophysical studies indicate that early experience of complex sounds has a profound impact on auditory perception and perceptual behaviors. Experience with speech, for instance, shapes language-specific phonemic perception, enhancing perceptual contrasts of native speech sounds and reducing perceptual contrasts of some foreign speech sounds. At the electrophysiological level, auditory cortical neurons preferentially respond to certain complex sounds, such as species-specific animal vocalizations. It is unclear how such selectivity for a complex sound emerges, and whether it is innate or shaped by early experience. In order to address this question, we exposed rat pups to a frequency-modulated (FM) sweep in different time windows during early development, and examined the effects of such sensory experience on sound representations in the primary auditory cortex (AI). We found that early exposure to an FM sound resulted in altered characteristic frequency representations and broadened spectral tuning in AI neurons. In contrast, later exposure to the same sound only led to greater selectivity for the sweep rate and direction of the experienced FM sound. These results indicate that cortical representations of different acoustic features are shaped by complex sounds in a series of distinct critical periods. Next, we confirmed this model of brain development in a set of experiments that examine how exposure to noise affects these various critical periods. We examined the influence of pulsed noise experience on the development of sound representations in AI. In naïve animals, FM sweep direction selectivity depends on the characteristic frequency (CF) of the neuron--low CF neurons tend to select for upward sweeps and high CF neurons for downward sweeps. Such a CF dependence was not observed in animals that had received weeklong exposure to pulsed noise in periods from postnatal day 8 (P8) to P15 or from P24 to P39. In addition, AI tonotopicity, tuning bandwidth, intensity threshold, tone-responsiveness, and sweep response magnitude were differentially affected by the noise experience depending on the exposure time windows. These results are consistent with previous findings of feature-dependent multiple sensitive periods. The different effects induced here by pulsed noise and previously by FM sweeps further indicate that plasticity in cortical complex sound representations is specific to the sensory input. Identifying how the developing brain processes sensory information provides a foundation for understanding more complex behaviors. These results advance our understanding of the neuronal mechanisms underlying sensory development and language learning. Specifically, they elucidate the age-dependent effects of complex sound exposure on spectral tuning and complex sound representation in the rat primary auditory cortex. In addition, they provide a foundation for subsequent studies investigating the neural basis of language development.

Author: Maryse Thomas
Publisher:
ISBN:
Category :
Languages : en
Pages :

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"The ability of the brain to change in response to its external environment is known as experience-dependent plasticity. Robust experience-dependent plasticity is typically restricted to early stages of life, when developing neural circuits are readily shaped by passive sensory experience. In the auditory system, for example, exposing juvenile but not adult rats to pure tones produces a functional over-representation of the tone frequency in the cortical tonotopic map. Recent studies have revealed the continued potential for passive experience to induce robust plasticity in the adult brain, however. In particular, chronic exposures to uninformative or disruptive sounds, such as white noise, have been shown to alter experience-dependent plasticity in the adult auditory cortex, returning the brain to a more plastic and juvenile state. This phenomenon provides an opportunity to study unprecedented cortical plasticity late in life, yet also reveals the brain’s vulnerability to abnormal sensory environments. Tackling both issues, the present thesis uses white noise as a tool to probe experience-dependent plasticity in the adult rat auditory cortex in three studies. In the first study, passive exposures to non-traumatic white noise of varying amplitude modulation depths are used to show the importance of salient temporal inputs for mature auditory function. Exposure to unmodulated but not modulated noise induces juvenile-like plasticity and frequency over-representation in response to a second exposure to pure tones, demonstrating that white noise triggers plasticity by masking temporal inputs from the environment. Since greater functional representation is generally thought to improve perceptual discrimination, the hypothesis that noise-induced plasticity could be used to improve adult perceptual learning is tested in the second study. Contrary to our expectations, sound-exposed animals were worse at discriminating the over-represented frequency, demonstrating that increased functional representation is not sufficient to improve discrimination. Finally, the third study investigates the possibility that changes in neural activity induced by noise exposure could be indicative of maladaptive plasticity leading to aberrant or unwanted perceptual consequences. Common neural and behavioral correlates of the auditory disorders tinnitus and hyperacusis were assessed in noise-exposed animals. Evidence of hyperacusis in exposed rats suggests that noise exposure opens windows of plasticity that may be understood as windows of vulnerability to maladaptive plastic changes. The results presented in this thesis help to elucidate the mechanisms and perceptual consequences of noise-induced plasticity in the adult rat auditory cortex. They describe the profound impact of noise on brain structure and function, advance our present understanding of experience-dependent plasticity in sensory circuits, and demonstrate how sensory environments may powerfully influence the brain throughout life"--

Author: Yale E. Cohen
Publisher: Springer Science & Business Media
ISBN: 1461423503
Category : Medical
Languages : en
Pages : 336

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Book Description
Hearing and communication present a variety of challenges to the nervous system. To be heard and understood, a communication signal must be transformed from a time-varying acoustic waveform to a perceptual representation to an even more abstract representation that integrates memory stores with semantic/referential information. Finally, this complex, abstract representation must be interpreted to form categorical decisions that guide behavior. Did I hear the stimulus? From where and whom did it come? What does it tell me? How can I use this information to plan an action? All of these issues and questions underlie auditory cognition. Since the early 1990s, there has been a re-birth of studies that test the neural correlates of auditory cognition with a unique emphasis on the use of awake, behaving animals as model. Continuing today, how and where in the brain neural correlates of auditory cognition are formed is an intensive and active area of research. Importantly, our understanding of the role that the cortex plays in hearing has the potential to impact the next generation of cochlear- and brainstem-auditory implants and consequently help those with hearing impairments. Thus, it is timely to produce a volume that brings together this exciting literature on the neural correlates of auditory cognition. This volume compliments and extends many recent SHAR volumes such as Sound Source Localization (2005) Auditory Perception of Sound Sources (2007), and Human Auditory Cortex (2010). For example, in many of these volumes, similar issues are discussed such as auditory-object identification and perception with different emphases: in Auditory Perception of Sound Sources, authors discuss the underlying psychophysics/behavior, whereas in the Human Auditory Cortex, fMRI data are presented. The unique contribution of the proposed volume is that the authors will integrate both of these factors to highlight the neural correlates of cognition/behavior. Moreover, unlike other these other volumes, the neurophysiological data will emphasize the exquisite spatial and temporal resolution of single-neuron [as opposed to more coarse fMRI or MEG data] responses in order to reveal the elegant representations and computations used by the nervous system.

Author: Jessica Liberty Sackville Hamilton
Publisher:
ISBN:
Category :
Languages : en
Pages : 104

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Book Description
The brain contains neurons of many different types interacting in complex functional circuits. To process sensory information these cells work in concert to form representations of the external world. In the auditory cortex, this involves integrating information from different cell types across an orderly anatomical structure of layers and columns. Representations can be observed at the level of single cells, cortical microcircuits, and large-scale sensory maps. The relationship between single cell properties and circuits within the auditory cortex, however, is still poorly understood. Furthermore, the structure-function relationships uncovered by neuroscientific study may crucially depend on the stimuli used to probe the system. This thesis brings together work from each of these different levels to describe how sounds are represented in the cortex, how this representation changes with experience, and how different cells contribute to cortical representation. First, I describe how the statistics of sound stimuli influence response properties in the mouse primary auditory cortex by comparing responses to pure tones and natural sounds (ultrasonic vocalizations). I also compare these responses to a temporally reversed vocalization to determine whether a sound with similar spectrotemporal content but no ethological relevance is represented similarly. When comparing pure tones and vocalizations, I find that the temporal response properties are similar, but that spectral response properties (e.g. frequency selectivity) often differ substantially. In particular, there are multiple sites that responded to vocalizations with frequency content outside their classical tone-derived receptive field, suggesting some specificity for behaviorally relevant sounds. When comparing forward and backward vocalizations, temporal responses are similar, but frequency bandwidth and characteristic frequency differs significantly across the population. Thus, the behaviorally relevant sound appears to be represented differently from non-behaviorally relevant synthetic and naturalistic sounds. The response properties of auditory neurons are not fixed, but rather depend on experience. In the next study, I examine how exposure to pulsed noise during different sensitive windows of the auditory critical period affects single site properties as well as circuit-level dynamics. On the single site level, I find that early exposure to pulsed noise increases receptive field thresholds and decreases frequency selectivity, while late noise exposure increases frequency bandwidths as well as spontaneous and evoked firing rates. To describe changes in functional microcircuits, I use the Ising model, which describes pairwise interactions between simultaneously recorded sites in the auditory cortex as well as interactions between sites and the stimuli that modulate them. I find that early noise exposure decreases stimulus drive, whereas late noise exposure does not change the strength of sound inputs but rather decreases the spread of functional connections from the deep to the superficial layers across sites with different frequency selectivity. Finally, I use a combination of optogenetic tools and computational methods to describe how the activity of a specific class of inhibitory neurons affects network connectivity in the auditory cortex. I examine the contribution of parvalbumin-positive (PV+) inhibitory interneurons, which make up around half of the inhibitory neurons in the cortex. These neurons are known to be involved in the generation of gamma oscillations, and their maturation corresponds with the end of the auditory critical period for plasticity. Using Ising models in tandem with linear-nonlinear vector autoregressive models, I show that stimulating PV+ neurons increases feedforward information flow through cortical circuits without changing lateral interactions within the same layers.

Author: Hania Kover
Publisher:
ISBN:
Category :
Languages : en
Pages : 160

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Book Description
During an early epoch of development, the brain is highly adaptive to the stimulus environment. Repeatedly exposing young animals to a particular tone, for example, leads to an enlarged representation of that tone in primary auditory cortex. While the neural effects of simple, single-frequency tonal environments are well characterized, the principles that guide plasticity in complex tone environments, as well as the perceptual consequences of cortical plasticity, remain unclear. To address these questions, this dissertation documents the neural and perceptual effects of simple and complex manipulations to the early acoustic environment. First, I show that rearing rat pups in a multi-tone environment leads to complex primary cortical representational changes that are related to the statistical relationships between experienced sounds. Specifically, tones that occur together within short temporal sequences tend to be represented by the same groups of neurons, whereas tones that occur separately are represented separately. This suggests that the development of primary auditory cortical response properties is sensitive to higher-order statistical relationships between sounds. The observed neural changes are accompanied by perceptual changes. Discrimination ability for sounds that never occur together within temporal sequences is improved. Heightened perceptual sensitivity is correlated with heightened neuronal response contrasts. These results suggest that early experience-dependent neural changes can mediate perceptual changes that may be related to statistical learning. Finally, I develop and experimentally test a model of the relationship between cortical sensory representations and perception. The model suggests that cortical stimulus representations may function as the neural representation of previously encountered stimulus probabilities, and makes predictions about how changes in these representations should affect perception within a statistical inference framework. Preliminary behavioral results support the model predictions, suggesting that one function of early experience-dependent plasticity may be to internalize stimulus distributions to shape future perception and behavior.

Author: Thomas D. Wickens
Publisher: Oxford University Press
ISBN: 9780195357806
Category : Psychology
Languages : en
Pages : 284

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Book Description
Signal detection theory, as developed in electrical engineering and based on statistical decision theory, was first applied to human sensory discrimination about 40 years ago. The theory's intent was to explain how humans discriminate and how we might use reliable measures to quantify this ability. An interesting finding of this work is that decisions are involved even in the simplest of discrimination tasks--say, determining whether or not a sound has been heard (a yes-no decision). Detection theory has been applied to a host of varied problems (for example, measuring the accuracy of diagnostic systems, survey research, reliability of lie detection tests) and extends far beyond the detection of signals. This book is a primer on signal detection theory, useful for both undergraduates and graduate students.

Author: Heesoo Kim
Publisher:
ISBN:
Category :
Languages : en
Pages : 94

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Book Description
The early acoustic environment plays a crucial role in how the brain represents sounds and how language phonemes are perceived. Human infants are born with the capacity to distinguish phonemes from virtually all languages, but very quickly change their perceptual ability to match that of their primary language. This has been described as the Perceptual Magnet Effect in humans, where phoneme tokens are perceived to be more similar than they physically are, leading to decreased discrimination ability. Early development is marked by distinct critical periods, when cortical regions are highly plastic and particularly sensitive to sensory input. These lasting alterations in cortical sensory representation may directly impact the perception of the external world. My thesis is comprised of three different studies, all of which investigate the role of the developmental acoustic environment on cortical representation and the behavioral consequence of altered cortical representation. Passive exposure to pure-tone pips during the auditory critical period can lead to over-representation of the exposure tone frequency in the primary auditory cortex (A1) of rats. This over-representation is associated with decreased discrimination ability of that frequency, similar to the Perceptual Magnet Effect in humans. Another hallmark of human language is categorical perception. Using a computational model of A1, I show that certain representation patterns (which may be achieved with passive exposure to two distinct pure-tone pips) in A1 can lead to categorical perception in rats. This suggests that cortical representation may be a mechanism that drives categorical perception. Rodents are socially vocal animals whose con-specific calls are often presented in bouts in the ultrasonic frequency range. These calls are vocalized at ethologically relevant repetition rates. I show that pure-tone pips that are presented at the ethological repetition rate (but not slower or faster rates) during the auditory critical period lead to over-representation of the pure-tone frequency. A certain subclass of ultrasonic vocalizations, the pup isolation calls, occurs during the auditory critical period. I show that there is over representation of ultrasonic vocalization frequencies in the rat A1. This preferential representation is experience-dependent and is associated with higher discrimination ability.

Author: Hans Menning
Publisher: GRIN Verlag
ISBN: 3638340554
Category : Psychology
Languages : en
Pages : 128

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Book Description
Doctoral Thesis / Dissertation from the year 2002 in the subject Psychology - Biological Psychology, grade: magna cum laude, University of Münster (Institute for Experimental Audiology), language: English, abstract: The motivation for this thesis came from the intriguing idea that we continuously restructure our brain through everyday learning. How can this highly complex, highly adaptive “learning device” change and reorganize itself all the time while keeping the illusion that we are constantly “ourselves”? The question is, whether learning has the power to trigger functional and structural changes in the brain. Several levels of thinking are involved in an interdisciplinary way. Thus, on a psychological level, 3 major topics enter this work: learning, memory and preconscious or pre-attentive perception and processing of information. Pre-attentive perception means that the subjects' attention and awareness is not mirrored in the neuronal response at a great deal. Learning is involved in this study as an improving discrimination of fine frequency and word duration differences; the latter was examined in a group of native and non-native speakers. Memory is referred to as sensory memory, a short-time memory trace that is established through the repetition of the same “standard” stimulus. In the auditory modality this has been termed “echoic memory”. A long, repetitive training engraves deep “traces” into the memory. The lifelong training of one’s native language results in a very fast and highly automated long-term memory access. On a neurophysiological level the main topics are plasticity and the reorganization of the underlying representational brain areas. Plastic changes on a molecular, synaptic and neuronal level and reorganization of cortical “maps” have been demonstrated abundantly in animal studies. On a physical level the measured magnetic fields and the calculation of the source parameters of their underlying neural generators are discussed in the light of the neurophysiological and psychological phenomena. Therefore, the aim of this dissertation thesis was, to transfer the insights of animal plasticity research onto the human brain and to draw a connection line between discrimination learning and the underlying neurophysiological changes. In a second step, these effects of discrimination learning are tested on speech perception.

Author: Jeffery A. Winer
Publisher: Springer Science & Business Media
ISBN: 0387270833
Category : Science
Languages : en
Pages : 720

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Book Description
Connecting the auditory brain stem to sensory, motor, and limbic systems, the inferior colliculus is a critical midbrain station for auditory processing. Winer and Schreiner's The Inferior Colliculus, a critical, comprehensive reference, presents the current knowledge of the inferior colliculus from a variety of perspectives, including anatomical, physiological, developmental, neurochemical, biophysical, neuroethological and clinical vantage points. Written by leading researchers in the field, the book is an ideal introduction to the inferior colliculus and central auditory processing for clinicians, otolaryngologists, graduate and postgraduate research workers in the auditory and other sensory-motor systems.