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Intermediate Storage (intermediate + storage)
Selected AbstractsElements of a neurobiological theory of hippocampal function: the role of synaptic plasticity, synaptic tagging and schemasEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2006R. G. M. MorrisArticle first published online: 8 JUN 200 Abstract The 2004 EJN Lecture was an attempt to lay out further aspects of a developing neurobiological theory of hippocampal function [Morris, R.G.M., Moser, E.I., Riedel, G., Martin, S.J., Sandin, J., Day, M. & O'Carroll, C. (2003) Phil. Trans. R. Soc. Lond. B Biol. Sci., 358, 773,786.] These are that (i) activity-dependent synaptic plasticity plays a key role in the automatic encoding and initial storage of attended experience; (ii) the persistence of hippocampal synaptic potentiation over time can be influenced by other independent neural events happening closely in time, an idea with behavioural implications for memory; and (iii) that systems-level consolidation of memory traces within neocortex is guided both by hippocampal traces that have been subject to cellular consolidation and by the presence of organized schema in neocortex into which relevant newly encoded information might be stored. Hippocampal memory is associative and, to study it more effectively than with previous paradigms, a new learning task is described which is unusual in requiring the incidental encoding of flavour,place paired associates, with the readout of successful storage being successful recall of a place given the flavour with which it was paired. NMDA receptor-dependent synaptic plasticity is shown to be critical for the encoding and intermediate storage of memory traces in this task, while AMPA receptor-mediated fast synaptic transmission is necessary for memory retrieval. Typically, these rapidly encoded traces decay quite rapidly over time. Synaptic potentiation also decays rapidly, but can be rendered more persistent by a process of cellular consolidation in which synaptic tagging and capture play a key part in determining whether or not it will be persistent. Synaptic tags set at the time of an event, even many trivial events, can capture the products of the synthesis of plasticity proteins set in train by events before, during or even after an event to be remembered. Tag,protein interactions stabilize synaptic potentiation and, by implication, memory. The behavioural implications of tagging are explored. Finally, using a different protocol for flavour,place paired associate learning, it is shown that rats can develop a spatial schema which represents the relative locations of several different flavours of food hidden at places within a familiar space. This schema is learned gradually but, once acquired, enables new paired associates to be encoded and stored in one trial. Their incorporation into the schema prevents rapid forgetting and suggests that schema play a key and hitherto unappreciated role in systems-level memory consolidation. The elements of what may eventually mature into a more formal neurobiological theory of hippocampal memory are laid out as specific propositions with detailed conceptual discussion and reference to recent data. [source] TOWARDS A UNIFORM CONCEPT FOR THE COMPARISON AND EXTRAPOLATION OF ROCKWALL RETREAT AND ROCKFALL SUPPLYGEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 1 2007MICHAEL KRAUTBLATTER ABSTRACT. Rates of rockwall retreat and rockfall supply are fundamental components of sediment budgets in steep environments. However, the standard procedure of referencing rockwall retreat rates using only lithology is inconsistent with research findings and results in a variability that exceeds three orders of magnitude. The concept proposed in this paper argues that the complexity inherent in rockfall studies can be reduced if the stages of (i) backweathering, (ii) filling and depletion of intermediate storage on the rock face and (iii) final rockfall supply onto the talus slopes are separated as these have different response functions and controlling factors. Backweathering responds to preweathering and weathering conditions whereas the filling and depletion of intermediate storage in the rock face is mainly a function of internal and external triggers. The noise apparent in backweathering rates and rockfall supply can be reduced by integrating the relevant controlling factors in the response functions. Simple conceptual models for the three stages are developed and are linked by a time-dependent ,rockfall delivery rate', which is defined as the difference between backweathering and rockfall supply, thus reflecting the specific importance of intermediate storage in the rock face. Existing studies can be characterized according to their ,rockfall delivery ratio', a concept similar to the ,sediment delivery ratio' used in fluvial geomorphology. Their outputs can be qualified as trigger-dependent rockfall supply rates or backweathering rates dependent on (pre-)weathering conditions. It is shown that the existing quantitative backweathering and rockfall supply models implicitly follow the proposed conceptual models and can be accommodated into the uniform model. Suggestions are made for how best to incorporate non-linearities, phase transitions, path dependencies and different timescales into rockfall response functions. [source] An fMRI study of canonical and noncanonical word order in GermanHUMAN BRAIN MAPPING, Issue 10 2007Jörg Bahlmann Abstract Understanding a complex sentence requires the processing of information at different (e.g., phonological, semantic, and syntactic) levels, the intermediate storage of this information and the unification of this information to compute the meaning of the sentence information. The present investigation homed in on two aspects of sentence processing: working memory and reanalysis. Event-related functional MRI was used in 12 healthy native speakers of German, while they read sentences. Half of the sentences had unambiguous initial noun-phrases (masculine nominative, masculine accusative) and thus signaled subject-first (canonical) or object-first (noncanonical) sentences. Noncanonical unambiguous sentences were supposed to entail greater demand on working memory, because of their more complex syntactic structure. The other half of the sentences had case-ambiguous initial noun-phrases (feminine gender). Only the second unambiguous noun-phrase (eighth position in the sentences) revealed, whether a canonical or noncanonical word order was present. Based on previous data it was hypothesized that ambiguous noncanonical sentences required a recomputation of the sentence, as subjects would initially commit to a subject first reading. In the respective contrasts two main areas of brain activation were observed. Unambiguous noncanonical sentences elicited more activation in left inferior frontal cortex relative unambiguous canonical sentences. This was interpreted in conjunction with the greater demands on working memory in the former condition. For noncanonical ambiguous relative to canonical ambiguous sentences, an activation of the left supramarginal gyrus was revealed, which was interpreted as a reflection of the reanalysis-requirements induced by this condition. Hum Brain Mapp, 2007. © 2007 Wiley-Liss, Inc. [source] Comparison of performance of heat regenerators: Relation between heat transfer efficiency and pressure dropINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 4 2001Françoise Duprat Abstract Heat regenerators transfer heat from one gas to another, with an intermediate storage in solids. The heat transfer surface for gas flow application should provide at the same time high surface area and low friction factor. Three geometries of heat transfer surface, monolith, stack of woven screens and bed of spheres, have been compared. Their performance was evaluated from the pressure drop of the heat regenerator working at a given heat transfer efficiency. The comparison was performed using numerical simulation and published measurements of heat transfer and flow friction characteristics. By adjusting the length and the period of the exchanger, it is possible to obtain the same heat transfer efficiency with the three geometries. Beds of spheres give very short and compact heat regenerators, working at high pressure drop. At the opposite, monoliths form long regenerators working at low pressure drop. Stacks of woven screens cover a wide range of performance: low porosity woven screens give high heat transfer efficiency and high pressure drop, while high porosity woven screens offer performance similar to that of the monoliths. Copyright © 2001 John Wiley & Sons, Ltd. [source] | ||||||||||