The Auditory Cortex

  • Filename: the-auditory-cortex.
  • ISBN: 1441900748
  • Release Date: 2010-12-02
  • Number of pages: 715
  • Author: Jeffery A. Winer
  • Publisher: Springer Science & Business Media

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.

The Human Auditory Cortex

  • Filename: the-human-auditory-cortex.
  • ISBN: 9781461423140
  • Release Date: 2012-04-11
  • Number of pages: 398
  • Author: David Poeppel
  • Publisher: Springer Science & Business Media

We live in a complex and dynamically changing acoustic environment. To this end, the auditory cortex of humans has developed the ability to process a remarkable amount of diverse acoustic information with apparent ease. In fact, a phylogenetic comparison of auditory systems reveals that human auditory association cortex in particular has undergone extensive changes relative to that of other species, although our knowledge of this remains incomplete. In contrast to other senses, human auditory cortex receives input that is highly pre-processed in a number of sub-cortical structures; this suggests that even primary auditory cortex already performs quite complex analyses. At the same time, much of the functional role of the various sub-areas in human auditory cortex is still relatively unknown, and a more sophisticated understanding is only now emerging through the use of contemporary electrophysiological and neuroimaging techniques. The integration of results across the various techniques signify a new era in our knowledge of how human auditory cortex forms basis for auditory experience. This volume on human auditory cortex will have two major parts. In Part A, the principal methodologies currently used to investigate human auditory cortex will be discussed. Each chapter will first outline how the methodology is used in auditory neuroscience, highlighting the challenges of obtaining data from human auditory cortex; second, each methods chapter will provide two or (at most) three brief examples of how it has been used to generate a major result about auditory processing. In Part B, the central questions for auditory processing in human auditory cortex are covered. Each chapter can draw on all the methods introduced in Part A but will focus on a major computational challenge the system has to solve. This volume will constitute an important contemporary reference work on human auditory cortex. Arguably, this will be the first and most focused book on this critical neurological structure. The combination of different methodological and experimental approaches as well as a diverse range of aspects of human auditory perception ensures that this volume will inspire novel insights and spurn future research.

The Auditory Cortex

  • Filename: the-auditory-cortex.
  • ISBN: 9781135613365
  • Release Date: 2005-05-06
  • Number of pages: 512
  • Author: Peter Heil
  • Publisher: Psychology Press

Understanding human hearing is not only a scientific challenge but also a problem of growing social and political importance, given the steadily increasing numbers of people with hearing deficits or even deafness. This book is about the highest level of hearing in humans and other mammals. It brings together studies of both humans and animals thereby giving a more profound understanding of the concepts, approaches, techniques, and knowledge of the auditory cortex. All of the most up-to-date procedures of non-invasive imaging are employed in the research that is described.

Neural Mechanisms for Call Processing in the Auditory Cortex of Mustached Bats Frequency Modulated Sounds and Their Lateralization

  • Filename: neural-mechanisms-for-call-processing-in-the-auditory-cortex-of-mustached-bats-frequency-modulated-sounds-and-their-lateralization.
  • ISBN: 9780549739272
  • Release Date: 2008
  • Number of pages: 102
  • Author:
  • Publisher: ProQuest

Speech processing is lateralized to the left hemisphere of the human brain, with some variation between sexes. Single unit electrophysiological recordings in the Doppler-shifted constant frequency processing (DSCF) sub-region of the mustached bat primary auditory cortex (A1) has revealed a left hemispheric advantage for processing species-specific (or conspecific) calls that at least superficially resembles the hemispheric specialization observed in humans. The hemispheric specialization for speech in humans has been related to an advantage of the left auditory cortex for processing information with a high temporal resolution, and, thus, the discovery of a similar mechanism in mustached bats would further demonstrate the similarity between lateralization for communication sounds in humans and bats. The first half of the research described herein is focused on the processing of frequency modulations (FMs) within the DSCF area, which comprises 30-50% of A1 in the bat. The second half is focused on observed hemispheric differences in the FM selectivity of DSCF neurons, specifically the peak response latency and magnitude elicited by FMs of varying slope and bandwidth. Results presented here demonstrate that not only are DSCF neurons responsive to FMs but also the left DSCF area responds more quickly and robustly to steep, broad-band FMs than do right DSCF neurons. Processing of relatively steep FMs requires finer temporal resolution than processing of relatively shallow FMs. Further, on average, hemispheric differences appear to be greater in male as opposed to female bats, reflecting a pattern previously observed in humans. Since the conspecific calls of bats are largely composed of FMs that widely vary in instantaneous modulation slope, this left hemispheric advantage for processing steep FMs can be considered a mechanism for the previously observed left hemispheric advantage for processing calls.

Synaptogenesis in the Auditory Cortex of Hearing and Deafened Rats

  • Filename: synaptogenesis-in-the-auditory-cortex-of-hearing-and-deafened-rats.
  • ISBN: 9780549741770
  • Release Date: 2008
  • Number of pages: 134
  • Author:
  • Publisher: ProQuest

The tonotopic organization of the rat auditory cortex is a modifiable entity, sensitive to acoustic manipulations during and, to a lesser degree, after the developmental auditory cortical critical period. Dendritic spine formation and remodeling is a dynamic process that is influenced by neural activity. The structural correlates underlying tonotopic map development and reorganization are poorly understood. My dissertation used the rat auditory cortex as a system to probe the effects of activity on synaptogenesis in vivo and to characterize the structural development of the auditory cortex in hearing and deafened conditions. To this end, I utilized DiOlistic labeling techniques to assess dendritic protrusion acquisition, dendritic spine maturation and dendritic arbor development. To begin, I performed a comprehensive investigation of synaptogenesis in the normal hearing rat. These studies found that dendritic protrusions were acquired slowly between postnatal day 4 (P4) and P9, rapidly between P9 and P19, and plateaued at mature densities by ∼P21. I developed a novel technique combining DiOlistics with bassoon, a presynaptic protein, immunohistochemistry to distinguish between immature filopodia and mature spines. I observed a rapid increase in the spines-to-filopodia ratio between P9 and P1 6. Together these data showed a period of rapid structural maturation between P9 and P16, coincident with hearing onset in the auditory cortex. Next, I investigated the role of early auditory input on cortical synaptogenesis. In deafened rats, dendritic protrusions were acquired at a similar rate as controls. Spine maturation was not affected by deafening, showing a similar increase in the spine-to-filopodium ratio from P9-P16. Dendritic arbor complexity revealed only minor differences in layer 4 pyramidal neuron dendrite formation. I also investigated the effects of deafening on dendritic spine maintenance. These results suggest divergent susceptibility of neurons and dendrites to activity-dependent spine maintenance. I next investigated whether the identity of synaptic information in auditory cortical neurons is different between hearing and deafened rats. I observed the increased ability of a visual stimulus to evoke activity in the auditory cortex in deafened rats, indicating increased visual-to-auditory cross-modal sensory plasticity.

Spatial Representation in Auditory Cortex of Marmoset Monkey

  • Filename: spatial-representation-in-auditory-cortex-of-marmoset-monkey.
  • ISBN: 9781109131147
  • Release Date: 2009
  • Number of pages: 247
  • Author:
  • Publisher: ProQuest

One of the fundamental tasks of the auditory system is to determine the spatial location of the acoustic stimulus. Although lesion studies suggest that the auditory cortex is essential for normal sound localization behavior, the role of auditory cortex in spatial hearing is still not well understood. In this thesis, we investigated the spatial tuning properties of neurons in the auditory cortex of awake marmosets. Compared with previous studies, our work explored the acoustic space more completely by using a speaker array covering the whole 360° space.

Association and Auditory Cortices

  • Filename: association-and-auditory-cortices.
  • ISBN: 9781475796193
  • Release Date: 2013-12-01
  • Number of pages: 360
  • Author: Alan Peters
  • Publisher: Springer Science & Business Media

This volume deals with some of the association areas of the cerebral cortex and with the auditory cortex. In the first chapter, by Deepak Pandya and Edward Yeterian, the general architectural features and connections of cortical associ ation areas are considered; as these authors point out, in primates the association areas take up a considerable portion of the total cortical surface. Indeed, it is the development of the association areas that accounts for the greatest differ ences between the brains of primate and non primate species, and these areas have long been viewed as crucial in the formation of higher cognitive and be havioral functions. In the following chapter, Irving Diamond, David Fitzpatrick, and James Sprague consider the question of whether the functions of the as sociation areas depend on projections from the sensory areas of the cortex. They use the visual cortex to examine this question and show that there is a great deal of difference between species in the amount of dependence, the differences being paralleled by variations in the manner in which the geniculate and pulvinar nuclei of the thalamus project to the striate and extra striate cortical areas. One of the more interesting and perhaps least understood of the association areas is the cingulate cortex, discussed by Brent Vogt. Cingulate cortex has been linked with emotion and with affective responses to pain, and in his chapter Vogt gives an account of its cytoarchitecture, connections, and functions.

Representation of Speech in the Primary Auditory Cortex and Its Implications for Robust Speech Processing

  • Filename: representation-of-speech-in-the-primary-auditory-cortex-and-its-implications-for-robust-speech-processing.
  • ISBN: 9780549781592
  • Release Date: 2008
  • Number of pages: 153
  • Author:
  • Publisher: ProQuest

Speech has evolved as a primary form of communication between humans. This most used means of communication has been the subject of intense study for years, but there is still a lot that we do not know about it. It is an oft repeated fact, that even the performance of the best speech processing algorithms still lags far behind that of the average human, It seems inescapable that unless we know more about the way the brain performs this task, our machines can not go much further. This thesis focuses on the question of speech representation in the brain, both from a physiological and technological perspective. We explore the representation of speech through the encoding of its smallest elements---phonemic features---in the primary auditory cortex. We report on how population of neurons with diverse tuning properties respond discriminately to phonemes resulting in explicit encoding of their parameters. Next, we show that this sparse encoding of the phonemic features is a simple consequence of the linear spectro-temporal properties of the auditory cortical neurons and that a Spectro-Temporal receptive field model can predict similar patterns of activation. This is an important step toward the realization of systems that operate based on the same principles as the cortex. Using an inverse method of reconstruction, we shall also explore the extent to which phonemic features are preserved in the cortical representation of noisy speech. The results suggest that the cortical responses are more robust to noise and that the important features of phonemes are preserved in the cortical representation even in noise. Finally, we explain how a model of this cortical representation can be used for speech processing and enhancement applications to improve their robustness and performance.

Plasticity in auditory cortex on the grounds of learning discrimination

  • Filename: plasticity-in-auditory-cortex-on-the-grounds-of-learning-discrimination.
  • ISBN: 9783638340557
  • Release Date: 2005-01-19
  • Number of pages: 125
  • Author: Hans Menning
  • Publisher: GRIN Verlag

Doctoral Thesis / Dissertation from the year 2002 in the subject Psychology - Biological Psychology, grade: magna cum laude, University of Münster (Institute for Experimental Audiology), 233 entries in the bibliography, 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.

Memory related Cognitive Modulation of Human Auditory Cortex Magnetoencephalography based Validation of a Computational Model

  • Filename: memory-related-cognitive-modulation-of-human-auditory-cortex-magnetoencephalography-based-validation-of-a-computational-model.
  • ISBN: 9780549572145
  • Release Date: 2008
  • Number of pages: 188
  • Author:
  • Publisher: ProQuest

It is well known that cognitive functions exert task-specific modulation of the response properties of human auditory cortex. However, the underlying neuronal mechanisms are not well understood yet. In this dissertation I present a novel approach for integrating 'bottom-up' (neural network modeling) and 'top-down' (experiment) methods to study the dynamics of cortical circuits correlated to short-term memory (STM) processing that underlie the task-specific modulation of human auditory perception during performance of the delayed-match-to-sample (DMS) task. The experimental approach measures high-density magnetoencephalography (MEG) signals from human participants to investigate the modulation of human auditory evoked responses (AER) induced by the overt processing of auditory STM during task performance. To accomplish this goal, a new signal processing method based on independent component analysis (ICA) was developed for removing artifact contamination in the MEG recordings and investigating the functional neural circuits underlying the task-specific modulation of human AER. The computational approach uses a large-scale neural network model based on the electrophysiological knowledge of the involved brain regions to simulate system-level neural dynamics related to auditory object processing and performance of the corresponding tasks. Moreover, synthetic MEG and functional magnetic resonance imaging (fMRI) signals were simulated with forward models and compared to current and previous experimental findings. Consistently, both simulation and experimental results demonstrate a DMS-specific suppressive modulation of the AER and corresponding increased connectivity between the temporal auditory and frontal cognitive regions. Overall, the integrated approach illustrates how biologically-plausible neural network models of the brain can increase our understanding of brain mechanisms and their computations at multiple levels from sensory input to behavioral output with the intermediate steps defined.

Characterization of Thalamorecipient Cells of Mouse Auditory Cortex in Vitro and in Silico

  • Filename: characterization-of-thalamorecipient-cells-of-mouse-auditory-cortex-in-vitro-and-in-silico.
  • ISBN: 9780549747666
  • Release Date: 2008
  • Number of pages: 206
  • Author:
  • Publisher: ProQuest

The mammalian neocortex is generally thought to play a fundamental role in most, if not all, higher cognitive functions including the conscious perception of sensory stimuli. Neurons in primary auditory cortex (AI) respond preferentially to specific aspects of auditory signals and receive their principal input concerning these signals from thalamic relay neurons in the ventral division of the medial geniculate nucleus (MGv). The aim of this thesis was to characterize the properties of thalamocortical synapses and intrinsic membrane properties of thalamorecipient cells in order elucidate the mechanisms that underlie the transformation of signals from thalamus to cortex. In vitro electrophysiology experiments showed that thalamorecipient cells of the mouse auditory cortex fall into two distinct, but heterogeneous, classes: regular-spiking, excitatory, pyramidal (RS) cells and fast-spiking, inhibitory (FS) interneurons. Fast-spiking inhibitory cells received inputs from thalamus that were of larger amplitude and exhibited greater short-term synaptic depression than those received by regular-spiking excitatory cells. A computational model of a thalamocortical circuit was constructed with parameters that were based on experimental data in order to elucidate the role of cellular properties in thalamocortical processing. The model showed that powerful feedforward inhibition and synaptic depression shape the temporal response properties of thalamorecipient cells in a dynamic way with depression acting to gate the effects of inhibition.

Feedforward Processing of Sounds in the Primary Auditory Cortex

  • Filename: feedforward-processing-of-sounds-in-the-primary-auditory-cortex.
  • ISBN: 9780549939818
  • Release Date: 2009
  • Number of pages: 227
  • Author:
  • Publisher: ProQuest

Neurons in the auditory system, up to the primary auditory cortex (A1), represent sounds by decomposing them into constituent frequencies. However, it is unclear what systematic computations are performed on these frequency-tuned receptive fields (RFs) to build more complex and selective RFs at higher stages of auditory processing. Therefore, we studied what computational principles may underlie feed-forward sound processing in the A1 of awake primates.

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