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Author: Jessica Liberty Sackville Hamilton Publisher: ISBN: Category : Languages : en Pages : 104
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: Jessica Liberty Sackville Hamilton Publisher: ISBN: Category : Languages : en Pages : 104
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: Josef Syka Publisher: Springer Science & Business Media ISBN: 0387231811 Category : Medical Languages : en Pages : 404
Book Description
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: Michele Nerissa Insanally Publisher: ISBN: Category : Languages : en Pages : 84
Book Description
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: Diedre D. De Souza Publisher: ISBN: Category : Languages : en Pages : 82
Book Description
Functional Magnetic Resonance Imaging (fMRI) was used to investigate the extent, magnitude and patterns of brain activity in response to frequency-modulated sounds. We examined this by manipulating the direction (rise vs. fall) and the rate (fast vs. slow) of a series of iterated rippled noise (IRN) bursts. Participants were presented with auditory stimuli while functional images of the cortex were obtained. Univariate analyses revealed more widespread activation within auditory cortex in response to frequency-modulated sweeps compared to steady-state sounds. Furthermore, multivoxel pattern analysis (MVPA) was used to determine whether regions within auditory cortex were involved in feature-specific encoding. The pattern of activity within auditory cortex showed a high degree of consistency for the rate dimension, suggesting this pattern of activity infers representational information. Additionally, activity patterns for direction were not distinguishable, which suggests this coding occurs over a neural activity pattern not distinguishable at the level of the BOLD response.
Author: Alexandre Kempf Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Perceptual objects are the elementary units used by the brain to construct an inner world representation of the environment from multiple physical sources, like light or sound waves. While the physical signals are first encoded by receptors in peripheral organs into neuroelectric signals, the emergence of perceptual object require extensive processing in the central nervous system which is not yet fully characterized. Interestingly, recent advances in deep learning shows that implementing series of nonlinear and linear operations is a very efficient way to create models that categorize visual and auditory perceptual objects similarly to humans. In contrast, most of the current knowledge about the auditory system concentrates on linear transformations. In order to establish a clear example of the contribution of auditory system nonlinearities to perception, we studied the encoding of sounds with an increasing intensity (up ramps) and a decreasing intensity (down ramps) in the mouse auditory cortex. Two behavioral tasks showed evidence that these two sounds are perceived with unequal salience despite carrying the same physical energy and spectral content, a phenomenon incompatible with linear processing. Recording the activity of large cortical populations for up- and down-ramping sounds, we found that cortex encodes them into distinct sets of non-linear features, and that asymmetric feature selection explained the perceptual asymmetry. To complement these results, we also showed that, in reinforcement learning models, the amount of neural activity triggered by a stimulus (e.g. a sound) impacts learning speed and strategy. Interestingly very similar effects were observed in sound discrimination behavior and could be explain by the amount of cortical activity triggered by the discriminated sounds. This altogether establishes that auditory system nonlinearities have an impact on perception and behavior. To more extensively identify the nonlinearities that influence sounds encoding, we then recorded the activity of around 60,000 neurons sampling the entire horizontal extent of auditory cortex. Beyond the fine scale tonotopic organization uncovered with this dataset, we identified and quantified 7 nonlinearities. We found interestingly that different nonlinearities can interact with each other in a non-trivial manner. The knowledge of these interactions carry good promises to refine auditory processing model. Finally, we wondered if the nonlinear processes are also important for multisensory integration. We measured how visual inputs and sounds combine in the visual and auditory cortex using calcium imaging in mice. We found no modulation of supragranular auditory cortex in response to visual stimuli, as observed in previous others studies. We observed that auditory cortex inputs to visual cortex affect visual responses concomitant to a sound. Interestingly, we found that auditory cortex projections to visual cortex preferentially channel activity from neurons encoding a particular non-linear feature: the loud onset of sudden sounds. As a result, visual cortex activity for an image combined with a loud sound is higher than for the image alone or combine with a quiet sound. Moreover, this boosting effect is highly nonlinear. This result suggests that loud sound onsets are behaviorally relevant in the visual system, possibly to indicate the presence of a new perceptual objects in the visual field, which could represent potential threats. As a conclusion, our results show that nonlinearities are ubiquitous in sound processing by the brain and also play a role in the integration of auditory information with visual information. In addition, it is not only crucial to account for these nonlinearities to understand how perceptual representations are formed but also to predict how these representations impact behavior.
Author: Huizhen Tang Publisher: ISBN: Category : Auditory cortex Languages : en Pages : 169
Book Description
Our ability to understand speech and other sounds relies crucially on the capacity to detect and perceive temporal amplitude fluctuations in the range of about 1-100 Hz. However, most individual neurons in auditory cortex are capable of precisely aligning their activities only to modulation rates at the lower end of this range. This raises the question of how higher modulation rates might be encoded, and of how the auditory cortex might be organised to accommodate the full range of perceptually relevant amplitude envelope modulations. Here we show, with noninvasive magnetoencephalography and electroencephalography measurements, that population oscillatory responses of human auditory cortex transition between a mode of strong phase locking to modulation rates below about 40-50 Hz, to a non phase-locked mode of responding at rates higher than about 50 Hz. Such dual response modes are predictable from the behaviours of single neurons in auditory cortex of non-human primates, but only the low rate phase locking mode has been previously observed in the neuronal population responses indexed in human MEG/EEG recordings. Taken together, the single neuron and MEG and EEG results from current thesis work suggest that two distinct types of neuronal encoding are required to represent the full range of temporal modulation rates that are relevant to everyday perception.
Author: Daniel Pressnitzer Publisher: Springer Science & Business Media ISBN: 9780387219158 Category : Science Languages : en Pages : 552
Book Description
This book contains the papers that were presented at the XIIIth International Symposium on Hearing (ISH), which was held in Dourdan, France, between August 24 and 29, 2003. From its first edition in 1969, the Symposium has had a distinguished tradition of bringing together auditory psychologists and physiologists. Hearing science now also includes computational modeling and brain imaging, and this is reflected in the papers collected. The rich interactions between participants during the meeting were yet another indication of the appositeness of the original idea to confront approaches around shared scientific issues. A total of 62 solicited papers are included, organized into 12 broad thematic areas ranging from cochlear signal processing to plasticity and perceptual learning. The themes follow the sessions and the chronological order of the paper presentations during the symposium. A notable feature of the ISH books is the transcription of the discussions between participants. A draft version of the book is circulated before the meeting, and all participants are invited to make written comments, before or during the presentations. This particularity is perhaps what makes the ISH book series so valuable as a truthful picture of the evolution of issues in hearing science. We tried to uphold this tradition, which was all the easier because of the excellent scientific content of the discussions.
Author: Paul F. Poon Publisher: Springer Science & Business Media ISBN: 1461553512 Category : Medical Languages : en Pages : 507
Book Description
The full power of combining experiment and theory has yet to be unleashed on studies of the neural mechanisms in the brain involved in acoustic information processing. In recent years, enormous amounts of physiological data have been generated in many laboratories around the world, characterizing electrical responses of neurons to a wide array of acoustic stimuli at all levels of the auditory neuroaxis. Modern approaches of cellular and molecular biology are leading to new understandings of synaptic transmission of acoustic information, while application of modern neuro-anatomical methods is giving us a fairly comprehensive view ofthe bewildering complexity of neural circuitry within and between the major nuclei of the central auditory pathways. Although there is still the need to gather more data at all levels of organization, a ma jor challenge in auditory neuroscience is to develop new frameworks within which existing and future data can be incorporated and unified, and which will guide future laboratory ex perimentation. Here the field can benefit greatly from neural modeling, which in the central auditory system is still in its infancy. Indeed, such an approach is essential if we are to address questions related to perception of complex sounds including human speech, to the many di mensions of spatial hearing, and to the mechanisms that underlie complex acoustico-motor behaviors.
Author: Jessica Liberty Sackville Hamilton
Author: Jessica Liberty Sackville Hamilton
Author: Josef Syka
Author: Michele Nerissa Insanally
Author: Diedre D. De Souza
Author: Alexandre Kempf
Author: Huizhen Tang
Author: Daniel Pressnitzer
Author: Tobias Overath
Author: Charles R. Heller
Author: Paul F. Poon