Pharmacological and Sensory Stimulation of Auditory Cortex Plasticity in Adult Rats PDF Download

Author: Vikram Jakkamsetti
Publisher:
ISBN:
Category : Auditory cortex
Languages : en
Pages : 182

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Book Description
In an adult rat, we paired acoustic input with injections of Rolipram-a drug that increases cortical cAMP levels and observed that Rolipram increased the length of the cortex activated by the paired tone and induced primary cortex neurons to become more selective to the paired tone. In the third part of the dissertation I explored induction of experience-dependent plasticity using modulation of attentional mechanisms. It has been previously demonstrated that paying attention to a tone for a tone discrimination task stimulates the nucleus basalis to release cortical acetylcholine which activates muscarinic M1 receptors to increase the representation of that tone in the primary auditory cortex. We paired acoustic input with injections of M1 agonist Cevemiline and observed an increase in the length of the cortex corresponding to the acoustic input. The experiments in this dissertation attempt to understand experience dependent brain changes and use current understanding of the mechanisms of experience dependent plasticity to research drugs that could help improve neuronal processing for neuronal disorders.

Author: Jennifer Lauren Hogsden Robinson
Publisher:
ISBN:
Category :
Languages : en
Pages : 232

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Book Description
Synaptic plasticity reflects the capacity of synapses to undergo changes in synaptic strength and connectivity, and is highly regulated by age and sensory experience. This thesis focuses on the characterization of synaptic plasticity in the primary auditory cortex (A1) of rats throughout development and following sensory deprivation. Initial experiments revealed an age-dependent decline in plasticity, as indicated by reductions in long-term potentiation (LTP). The enhanced plasticity of juvenile rats appeared to be mediated by NR2B subunits of the N-methyl-d-aspartate receptor (NMDAR), as NR2B antagonist application reduced LTP to adult-like levels in juveniles, yet had no effect in adults. The importance of sensory experience in mediating plasticity was revealed in experiments using white noise exposure, which is a sensory deprivation technique known to arrest cortical development in A1. Notably, adult rats reared in continuous white noise maintained more juvenile-like levels of LTP, which normalized upon subsequent exposure to an unaltered acoustic environment. The white noise-induced LTP enhancements also appeared to be mediated by NR2B subunits, as NR2B antagonists reversed these LTP enhancements in white noise-reared rats. Given the strong influence that sensory experience exerts on plasticity, additional experiments examined the effect of shorter episodes of white noise exposure on LTP in adult rats. Exposure to white noise during early postnatal life appeared to "prime" A1 for subsequent exposure in adulthood, resulting in enhanced LTP. The necessity of early-life exposure was evident, as repeated episodes of white noise in adulthood did not enhance plasticity. In older rats that typically no longer express LTP in A1, pharmacological methods to enhance plasticity were explored. Moderate LTP was observed in older rats with cortical zinc application, which may act through its antagonism of NR2A subunits of the NMDAR. Additionally, current source density and cortical silencing analyses were conducted to characterize the distinct peaks of field postsynaptic potentials recorded in A1, with the earlier and later peaks likely representing thalamocortical and intracortical synapses, respectively. Together, this thesis emphasizes the critical role of sensory experience in determining levels of cortical plasticity, and demonstrates strategies to enhance plasticity in the mature auditory cortex.

Author: Jose Miguel Cisneros-Franco
Publisher:
ISBN:
Category :
Languages : en
Pages :

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"Neuroplasticity refers to the brain’s ability to modify its connections and function in response to experience. This experience-dependent plasticity is necessary for the acquisition of new abilities during early development or in adult life, and plays a crucial role in recovery after a neurological injury. During early developmental epochs known as critical periods (CPs), passive experience alone can have profound and long-lasting effects in cortical sensory representations. In contrast, plasticity in the adult brain occurs almost exclusively in the context of perceptual learning (PL); i.e., the process whereby attention and repetition lead to long-lasting improvements in stimulus detection or sensory discrimination.Whether it occurs as a result of passive experience, PL, or other experimental interventions, cortical plasticity ultimately entails a change in activity patterns driven by a shift in the local levels of excitation and inhibition. And although cortical inhibitory interneurons constitute a clear minority compared to the number of excitatory neurons, they are instrumental in regulating both juvenile and adult experience-dependent plasticity. This thesis consists of three experimental studies that addressed critical and interrelated knowledge gaps regarding the inhibitory regulating mechanisms of experience-dependent plasticity, both in the context of changes in the environment and during PL. Using the rat primary auditory cortex (A1) as a model, we combined electrophysiological, anatomical, chemogenetic, and behavioral methodologies to address each study’s main hypotheses. In the first study we examined the role of inhibition in A1 plasticity across the lifespan. We found that reduced cortical inhibition in older adults was associated with an increased but poorly regulated plasticity when compared to younger adults. In older brains, however, changes elicited by auditory stimulation and training were rapidly lost, suggesting that such increased plasticity might be detrimental, as the older brains were unable to consolidate these changes. Importantly, increasing inhibition artificially with clinically available drugs restored the stability of sensory representations and improved the retention of plastic changes associated with PL.In the second study, we turned our attention to parvalbumin-positive (PV+) cells, the most common type of inhibitory neurons in the brain. Bidirectional manipulation of PV+ cell activity affected neuronal spectral and sound intensity selectivity, and, in the case of PV+ interneuron inactivation, was mirrored by anatomical changes in PV and associated perineuronal net expression. In addition, we showed that the inactivation of PV+ interneurons is sufficient to reinstate CP plasticity in the adult auditory cortex. In the third study, we investigated the role of PV+ cells in auditory PL. As previously reported in other cortical areas, training was associated with a transient downregulation of PV expression during early stages of training. We then examined the effects of prolonged PV+ cell manipulation throughout the training period. Our results suggest that, although reduced PV+ cell function may facilitate early training-related modifications in cortical circuits, a subsequent increase in PV+ cell activity is needed to prevent further plastic changes and consolidate learning. Taken together, our findings underscore the importance of sustained inhibitory neurotransmission in ensuring high fidelity discrimination of sensory inputs and in maintaining the stability of sensory representations. Our behavioral studies further suggest that such stability is necessary for the consolidation of complex skills that are built on basic sensory representations. Finally, the experimental work presented in this thesis also highlights the potential of pharmacological and chemogenetic approaches for harnessing cortical plasticity with the ultimate goal of aiding recovery from brain injury or disease"--

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: 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: Anna Menini
Publisher: CRC Press
ISBN: 1420071998
Category : Science
Languages : en
Pages : 438

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Book Description
Comprehensive Overview of Advances in OlfactionThe common belief is that human smell perception is much reduced compared with other mammals, so that whatever abilities are uncovered and investigated in animal research would have little significance for humans. However, new evidence from a variety of sources indicates this traditional view is likely

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.

Author: Rocío Fernández-Ballesteros
Publisher: Cambridge University Press
ISBN: 1108641431
Category : Psychology
Languages : en
Pages : 969

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Book Description
Recent studies show that more people than ever before are reaching old age in better health and enjoying that health for a longer time. This Handbook outlines the latest discoveries in the study of aging from bio-medicine, psychology, and socio-demography. It treats the study of aging as a multidisciplinary scientific subject, since it requires the interplay of broad disciplines, while offering high motivation, positive attitudes, and behaviors for aging well, and lifestyle changes that will help people to stay healthier across life span and in old age. Written by leading scholars from various academic disciplines, the chapters delve into the most topical aspects of aging today - including biological mechanisms of aging, aging with health, active and productive aging, aging with satisfaction, aging with respect, and aging with dignity. Aimed at health professionals as well as general readers, this Cambridge Handbook offers a new, positive approach to later life.

Author: Federico Bermudez-Rattoni
Publisher: CRC Press
ISBN: 1420008412
Category : Psychology
Languages : en
Pages : 368

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Book Description
A comprehensive, multidisciplinary review, Neural Plasticity and Memory: From Genes to Brain Imaging provides an in-depth, up-to-date analysis of the study of the neurobiology of memory. Leading specialists share their scientific experience in the field, covering a wide range of topics where molecular, genetic, behavioral, and brain imaging techniq

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.