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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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Abstract

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.

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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