Developmental Plasticity in the Auditory Cortex of the Cat PDF Download
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Languages : en
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Author: Susan Gay Stanton
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Category :
Languages : en
Pages : 0
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The consequences of an abnormal pattern of sensory input during development on the organization of the auditory cortex and the thalamocortical pathway were examined. Two different experimental paradigms were used to change the peripheral pattern of neural input to the system: (1) auditory deprivation: partial cochlear lesions were induced by treating newborn kittens with the ototoxic aminoglycoside drug amikacin and (2) auditory augmentation: newborn kittens were reared in an altered acoustic environment, consisting predominantly of a continuous 8 kHz FM tone. Standard microelectrode recording techniques were used to examine the functional organization of primary auditory cortex and revealed an altered cortical frequency map as a consequence of these experimental manipulations. Scanning electron microscopy (SEM) was used to examine the cochlea, and auditory brainstem responses (ABR audiogram) were used to measure frequency-specific threshold changes in ascending neural activity. Retrograde tracers were introduced in AI, and were used to examine the organization of the thalamocortical projection. As a result of neonatal partial cochlear lesions the cochleotopic organization of primary auditory cortex was altered, with the deprived high frequency region of AI devoted instead to the representation of low frequencies. Furthermore, the deafferented region of the cortical map displayed an abnormally large cortical area (expansion) with neurons having common characteristic frequencies. The range of characteristic frequencies within this monotonic cortical region corresponded to both the high frequency border of the hearing loss and the edge of the cochlear lesion. However, retrograde tracer injections into different regions in AI produced a normal pattern of labelling in the medial geniculate body of the thalamus. These results suggest that the cochleotopic organization of the thalamocortical projection is not disrupted in deafened cats, despite the extensive physiological reorganization of the cortical frequency map observed in these animals. As a consequence of rearing newborn kittens in an altered acoustic environment, the cochleotapic representation in AI also develops abnormally. Exposure to a continuous 8 kHz FM signal during a period from birth to three months of age produced a significant expansion of the 6-12 kHz frequency region of the cortical map in mature cats. These studies have shown that manipulating the pattern of cochlear activity during the neonatal period induces changes in the functional organization of the cochleotopic map in primary auditory cortex of the cat. In conclusion, the cochleotopic map within auditory cortex is altered in a manner which reflects the pattern of sensory input from the periphery during development.
Author: Theodore M. Moallem
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Category :
Languages : en
Pages : 110
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Author: David Mark Diamond
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Category :
Languages : en
Pages : 402
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Author: Jeffery A. Winer
Publisher: Springer Science & Business Media
ISBN: 1441900748
Category : Science
Languages : en
Pages : 711
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Book Description
There has been substantial progress in understanding the contributions of the auditory forebrain to hearing, sound localization, communication, emotive behavior, and cognition. The Auditory Cortex covers the latest knowledge about the auditory forebrain, including the auditory cortex as well as the medial geniculate body in the thalamus. This book will cover all important aspects of the auditory forebrain organization and function, integrating the auditory thalamus and cortex into a smooth, coherent whole. Volume One covers basic auditory neuroscience. It complements The Auditory Cortex, Volume 2: Integrative Neuroscience, which takes a more applied/clinical perspective.
Author: Heesoo Kim
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Category :
Languages : en
Pages : 94
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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: Josef Syka
Publisher: Springer Science & Business Media
ISBN: 0387231811
Category : Medical
Languages : en
Pages : 404
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The symposium that has provided the basis for this book, "Plasticity of the Central Auditory System and Processing of Complex Acoustic Signals" was held in Prague on July 7-10, 2003. This is the fourth in a series of seminal meetings summarizing the state of development of auditory system neuroscience that has been organized in that great world city. Books that have resulted from these meetings represent important benchmarks for auditory neuroscience over the past 25 years. A 1980 meeting, "Neuronal Mechanisms of Hearing" hosted the most distinguished hearing researchers focusing on underlying brain processes from this era. It resulted in a highly influential and widely subscribed and cited proceedings co-edited by professor Lindsay Aitkin. The subject of the 1987 meeting was the "Auditory Pathway - Structure and Function". It again resulted in another important update of hearing science research in a widely referenced book - edited by the late Bruce Masterton. While the original plan was to hold a meeting summarizing the state of auditory system neuroscience every 7 years, historical events connected with the disintegration of the Soviet Empire and return of freedom to Czechoslovakia resulted in an unavoidable delay of what was planned to be a 1994 meeting. It wasn't until 1996 that we were able to meet for the third time in Prague, at that time to review "Acoustical Signal Processing in the Central Auditory System".
Author: Charles Chulsoo Lee
Publisher:
ISBN:
Category :
Languages : en
Pages : 648
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Author: Hania Kover
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Category :
Languages : en
Pages : 160
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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 N. Parks
Publisher: Springer Science & Business Media
ISBN: 1475742193
Category : Science
Languages : en
Pages : 336
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Book Description
The auditory system has a remarkable ability to adjust to an ever-changing environment. The six review chapters that comprise Plasticity of the Central Auditory System cover a spectrum of issues concerning this ability to adapt, defined by the widely applicable term "plasticity". With chapters focusing on the development of the cochlear nucleus, the mammalian superior olivary complex, plasticity in binaural hearing, plasticity in the auditory cortex, neural plasticity in bird songs, and plasticity in the insect auditory system, this volume represents much of the most current research in this field. The volume is thorough enough to stand alone, but is closely related a previous SHAR volume, Development of the Auditory System (Volume 9) by Rubel, Popper, and Fay. The book fully addresses the difficulties, challenges, and complexities of this topic as it applies to the auditory development of a wide variety of species.
