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Determinants of synaptic information transfer: From Ca2+ binding proteins to Ca2+ signaling domains

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889198344 Year: Pages: 133 DOI: 10.3389/978-2-88919-834-4 Language: English
Publisher: Frontiers Media SA
Subject: Neurology --- Science (General)
Added to DOAB on : 2016-01-19 14:05:46
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The cytoplasmic free Ca2+ concentration ([Ca2+]i) is a key determinant of neuronal information transfer and processing. It controls a plethora of fundamental processes, including transmitter release and the induction of synaptic plasticity. This enigmatic second messenger conveys its wide variety of actions by binding to a subgroup of Ca2+ binding proteins (CaBPs) known as “Ca2+ sensors”. Well known examples of Ca2+ sensors are Troponin-C in skeletal muscle, Synaptotagmin in presynaptic terminals, and Calmodulin (CaM) in all eukaryotic cells. Since the levels of [Ca2+]i directly influence the potency of Ca2+ sensors, the Ca2+ concentration is tightly controlled by several mechanisms including another type of Ca2+ binding proteins, the Ca2+ buffers. Prominent examples of Ca2+ buffers include Parvalbumin (PV), Calbindin-D28k (CB) and Calretinin (CR), although for the latter two Ca2+ sensor functions were recently also suggested. Ca2+ buffers are distinct from sensors by their purely buffering action, i.e. they influence the spatio-temporal extent of Ca2+ signals, without directly binding downstream target proteins. Details of their action depend on their binding kinetics, mobility, and concentration. Thus, neurons can control the range of action of Ca2+ by the type and concentration of CaBPs expressed. Since buffering strongly limits the range of action of free Ca2+, the structure of the Ca2+ signaling domain and the topographical relationships between the sites of Ca2+ influx and the location of the Ca2+ sensors are central determinants in neuronal information processing. For example, postsynaptic dendritic spines act to compartmentalize Ca2+ depending on their geometry and expression of CaBPs, thereby influencing dendritic integration. At presynaptic sites it has been shown that tight, so called nanodomain coupling between Ca2+ channels and the sensor for vesicular transmitter release increases speed and reliability of synaptic transmission. Vice versa, the influence of an individual CaBP on information processing depends on the topographical relationships within the signaling domain. If e.g. source and sensor are very close, only buffers with rapid binding kinetics can interfere with signaling. This Research Topic contains a collection of work dealing with the relationships between different [Ca2+]i controlling mechanisms in the structural context of synaptic sites and their functional implications for synaptic information processing as detailed in the Editorial.

Inhibitory Function in Auditory Processing

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889196678 Year: Pages: 231 DOI: 10.3389/978-2-88919-667-8 Language: English
Publisher: Frontiers Media SA
Subject: Science (General) --- Neurology
Added to DOAB on : 2016-08-16 10:34:25
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There seems little doubt that from the earliest evolutionary beginnings, inhibition has been a fundamental feature of neuronal circuits - even the simplest life forms sense and interact with their environment, orienting or approaching positive stimuli while avoiding aversive stimuli. This requires internal signals that both drive and suppress behavior. Traditional descriptions of inhibition sometimes limit its role to the suppression of action potential generation. This view fails to capture the vast breadth of inhibitory function now known to exist in neural circuits. A modern perspective on inhibitory signaling comprises a multitude of mechanisms. For example, inhibition can act via a shunting mechanism to speed the membrane time constant and reduce synaptic integration time. It can act via G-protein coupled receptors to initiate second messenger cascades that influence synaptic strength. Inhibition contributes to rhythm generation and can even activate ion channels that mediate inward currents to drive action potential generation. Inhibition also appears to play a role in shaping the properties of neural circuitry over longer time scales. Experience-dependent synaptic plasticity in developing and mature neural circuits underlies behavioral memory and has been intensively studied over the past decade. At excitatory synapses, adjustments of synaptic efficacy are regulated predominantly by changes in the number and function of postsynaptic glutamate receptors. There is, however, increasing evidence for inhibitory modulation of target neuron excitability playing key roles in experience-dependent plasticity. One reason for our limited knowledge about plasticity at inhibitory synapses is that in most circuits, neurons receive convergent inputs from disparate sources. This problem can be overcome by investigating inhibitory circuits in a system with well-defined inhibitory nuclei and projections, each with a known computational function. Compared to other sensory systems, the auditory system has evolved a large number of subthalamic nuclei each devoted to processing distinct features of sound stimuli. This information once extracted is then re-assembled to form the percept the acoustic world around us. The well-understood function of many of these auditory nuclei has enhanced our understanding of inhibition's role in shaping their responses from easily distinguished inhibitory inputs. In particular, neurons devoted to processing the location of sound sources receive a complement of discrete inputs for which in vivo activity and function are well understood. Investigation of these areas has led to significant advances in understanding the development, physiology, and mechanistic underpinnings of inhibition that apply broadly to neuroscience. In this series of papers, we provide an authoritative resource for those interested in exploring the variety of inhibitory circuits and their function in auditory processing. We present original research and focused reviews touching on development, plasticity, anatomy, and evolution of inhibitory circuitry. We hope our readers will find these papers valuable and inspirational to their own research endeavors.

The Impact of Sensory; Linguistic and Social Deprivation on Cognition

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889453542 Year: Pages: 183 DOI: 10.3389/978-2-88945-354-2 Language: English
Publisher: Frontiers Media SA
Subject: Science (General) --- Psychology
Added to DOAB on : 2018-02-27 16:16:45
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Early experience plays a crucial role in determining the trajectory of cognitive development. For example, early sensory deprivation is known to induce neural reorganization by way of adaptation to the altered sensory experience. Neville and Bavelier’s “compensatory theory’’ hypothesizes that loss of one sense may bring about a sensory enhancement in the remaining modalities. Sensory deprivation will, however, also impact the age of emergence, or the speed of acquisition of cognitive abilities that depend upon sensory inputs. Understanding how a child’s early environment shapes their cognition is not only of theoretical interest. It is essential for the development of early intervention programs that address not just the early deprivation itself, but also the cognitive sequelae of such deprivation. The articles in this e-book all address different aspects of deprivation - sensory, linguistic, and social - and explore the impacts of such deprivation on a wide range of cognitive outcomes. In reading these contributions, it is important to note that sensory, linguistic, and social deprivation are not independent factors in human experience. For example, a child born deaf into a hearing family is likely to experience delays in exposure to natural language, with subsequent limits on their linguistic competence having an effect on social interactions and inclusion: a child raised in environments where social interaction is highly limited is also likely to experience reductions in the quantity and quality of linguistic inputs. Future work will need to carefully examine the complex interactions between the sensory, linguistic and social environments of children raised in atypical or impoverished environments.

How and Why Does Spatial-Hearing Ability Differ among Listeners? What Is the Role of Learning and Multisensory Interactions?

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889198566 Year: Pages: 253 DOI: 10.3389/978-2-88919-856-6 Language: English
Publisher: Frontiers Media SA
Subject: Psychology --- Neurology --- Science (General)
Added to DOAB on : 2016-01-19 14:05:46
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Spatial-hearing ability has been found to vary widely across listeners. A survey of the existing auditory-space perception literature suggests that three main types of factors may account for this variability:- physical factors, e.g., acoustical characteristics related to sound-localization cues,- perceptual factors, e.g., sensory/cognitive processing, perceptual learning, multisensory interactions,- and methodological factors, e.g., differences in stimulus presentation methods across studies.However, the extent to which these–and perhaps other, still unidentified—factors actually contribute to the observed variability in spatial hearing across individuals with normal hearing or within special populations (e.g., hearing-impaired listeners) remains largely unknown. Likewise, the role of perceptual learning and multisensory interactions in the emergence of a multimodal but unified representation of “auditory space,” is still an active topic of research. A better characterization and understanding of the determinants of inter-individual variability in spatial hearing, and of its relationship with perceptual learning and multisensory interactions, would have numerous benefits. In particular, it would enhance the design of rehabilitative devices and of human-machine interfaces involving auditory, or multimodal space perception, such as virtual auditory/multimodal displays in aeronautics, or navigational aids for the visually impaired. For this Research Topic, we have considered manuscripts that:- present new methods, or review existing methods, for the study of inter-individual differences;- present new data (or review existing) data, concerning acoustical features relevant for explaining inter-individual differences in sound-localization performance;- present new (or review existing) psychophysical or neurophysiological findings concerning spatial hearing and/or auditory perceptual learning, and/or multisensory interactions in humans (normal or impaired, young or older listeners) or other species;- discuss the influence of inter-individual differences on the design and use of assistive listening devices (rehabilitation) or human-machine interfaces involving spatial hearing or multimodal perception of space (ergonomy).

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