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Memory Model (memory + model)
Selected AbstractsAn analysis of VI Architecture primitives in support of parallel and distributed communicationCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 1 2002Andrew Begel Abstract We present the results of a detailed study of the Virtual Interface (VI) paradigm as a communication foundation for a distributed computing environment. Using Active Messages and the Split-C global memory model, we analyze the inherent costs of using VI primitives to implement these high-level communication abstractions. We demonstrate a minimum mapping cost (i.e. the host processing required to map one abstraction to a lower abstraction) of 5.4 ,s for both Active Messages and Split-C using four-way 550 MHz Pentium III SMPs and the Myrinet network. We break down this cost to the use of individual VI primitives in supporting flow control, buffer management and event processing and identify the completion queue as the source of the highest overhead. Bulk transfer performance plateaus at 44 Mbytes/s for both implementations are due to the addition of fragmentation requirements. Based on this analysis, we present the implications for the VI successor, Infiniband. Copyright © 2002 John Wiley & Sons, Ltd. [source] Working memory: Its role in dyslexia and other specific learning difficultiesDYSLEXIA, Issue 3 2004Sharman Jeffries Abstract This paper reports a study contrasting dyslexic children against a control group of children without special educational needs (SEN) and a group with varied SENs. Children's abilities were compared on tasks assessing phonological processing, visuo-spatial/motor coordination and executive/inhibitory functioning; being targeted for assessment based on theoretical proposals related to the working memory model. Primary and secondary school level children were tested: 21 assessed as dyslexic with no comorbid difficulties, 26 children assessed with difficulties including dyspraxia, emotional/behavioural problems and attention deficits, 40 children with no known education-related deficits were controls. Results indicated both SEN groups performed worse than controls on working memory phonological loop measures. However, SEN groups could only be differentiated on phonological awareness measures: the dyslexics showing lower scores. Dyslexics performed as well as controls on working memory visuo-spatial scratch pad measures and one of two additional visual,motor coordination tasks, whereas the performance of the other SEN children was lowest on the majority of these measures. Central executive and interference measures engendered mixed performances, both SEN groups showing evidence of deficits in one or more of these areas of functioning, although, of the two SEN groups, the dyslexics seem to have performed the worse when digit name processing was required. Copyright © 2004 John Wiley & Sons, Ltd. [source] Shapes of nonmonotonic activation functions in a chaotic neural network associative memory model and its evaluationELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 3 2008Masanao Obayashi Abstract The purpose of this paper is to investigate the performance of the associative memory model using Aihara's chaotic neural network with different activation functions. Sigmoid function, a monotonic function, was used in Aihara's original model. However, in the static associative memory, it is reported that the storage capacity of the network is improved when a nonmonotonic function is used as the activation function. To improve the associative ability of chaotic neural network, kinds of nonmonotonic functions have been proposed to serve as activation function. This paper investigates their difference as to retrieval ability, and proposes an advanced nonmonotonic function. By computer simulation, we discuss what kind of shape is good regarding improving the associative ability of chaotic neural network. © 2008 Wiley Periodicals, Inc. Electron Comm Jpn, 91(3): 22, 27, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10070 [source] Estradiol enhances long term potentiation in hippocampal slices from aged apoE4-TR miceHIPPOCAMPUS, Issue 12 2007Sung Hwan Yun Abstract Hormone replacement therapy to treat or prevent Alzheimer Disease (AD) in postmenopausal women is controversial because it may pose other health risks such as cancer and thromboembolism. ApoE status is thought to influence the nootropic efficacy of hormone therapy, but findings are neither consistent nor well understood. We used a known in vitro memory model (long-term potentiation, LTP) in aged (24,27 month) female targeted replacement mice expressing human apoE3 or E4 to compare the effects of exogenous estradiol. Recording medial perforant path evoked field potentials in dentate gyrus of hippocampal slices, we found that both strains exhibited comparable basal synaptic transmission as assessed by input/output functions and paired pulse depression, and that these measures were not affected by estradiol. Vehicle-treated groups from both strains showed comparable LTP. Estradiol had no effect on LTP in apoE3-TR, but selectively increased LTP magnitude in apoE4-TR. The estradiol induced enhancement of LTP in aged female apoE4-TR is consistent with recent clinical observations that estrogen replacement decreases AD risk in some women with apoE4. Elucidating the mechanism of this selective enhancement may lead to more informed treatment decisions as well as to the development of safer alternatives to hormone therapy. © 2007 Wiley-Liss, Inc. [source] Continuous classifying associative memoryINTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 4 2002Antonio B. Bailón In this article we present the so-called continuous classifying associative memory, able to store continuous patterns avoiding the problems of spurious states and data dependency. This is a memory model based on our previously developed classifying associative memory, which enables continuous patterns to be stored and recovered. We will also show that the behavior of this continuous classifying associative memory may be adjusted to some predetermined goals by selecting some internal operating functions. © 2002 Wiley Periodicals, Inc. [source] Parallel Fock matrix construction with distributed shared memory model for the FMO-MO methodJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 13 2010Hiroaki Umeda Abstract A parallel Fock matrix construction program for FMO-MO method has been developed with the distributed shared memory model. To construct a large-sized Fock matrix during FMO-MO calculations, a distributed parallel algorithm was designed to make full use of local memory to reduce communication, and was implemented on the Global Array toolkit. A benchmark calculation for a small system indicates that the parallelization efficiency of the matrix construction portion is as high as 93% at 1,024 processors. A large FMO-MO application on the epidermal growth factor receptor (EGFR) protein (17,246 atoms and 96,234 basis functions) was also carried out at the HF/6-31G level of theory, with the frontier orbitals being extracted by a Sakurai-Sugiura eigensolver. It takes 11.3 h for the FMO calculation, 49.1 h for the Fock matrix construction, and 10 min to extract 94 eigen-components on a PC cluster system using 256 processors. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010 [source] Verbal short-term memory in Down's syndrome: An articulatory loop deficit?JOURNAL OF INTELLECTUAL DISABILITY RESEARCH, Issue 2 2004S. Vicari Abstract Background Verbal short-term memory, as measured by digit or word span, is generally impaired in individuals with Down's syndrome (DS) compared to mental age-matched controls. Moving from the working memory model, the present authors investigated the hypothesis that impairment in some of the articulatory loop sub-components is at the base of the deficient maintenance and recall of phonological representations in individuals with DS. Methods Two experiments were carried out in a group of adolescents with DS and in typically developing children matched for mental age. In the first experiment, the authors explored the reliance of these subjects on the subvocal rehearsal mechanism during a word-span task and the effects produced by varying the frequency of occurrence of the words on the extension of the word span. In the second experiment, they investigated the functioning of the phonological store component of the articulatory loop in more detail. Results A reduced verbal span in DS was confirmed. Neither individuals with DS nor controls engaged in spontaneous subvocal rehearsal. Moreover, the data provide little support for defective functioning of the phonological store in DS. Conclusions No evidence was found suggesting that a dysfunction of the articulatory loop and lexical-semantic competence significantly contributed to verbal span reduction in subjects with DS. Alternative explanations of defective verbal short-term memory in DS, such as a central executive system impairment, must be considered. [source] What Have you Done for me Lately?THE ECONOMIC JOURNAL, Issue 518 2007Release of Information, Strategic Manipulation of Memories How should a rational agent (politician/employee/advertiser) release information in order to manipulate the memory imperfections of his forgetful assessor (electorate/supervisor/consumer)? This article attempts to answer this question using a memory model based on the principles of recency, similarity and repetition. I show that the problem of a rational agent who releases information to a forgetful assessor can be modelled as a standard dynamic optimisation problem and we describe the properties of the optimal profile for releasing information. The theoretical results are applicable in a wide range of social and economic contexts, such as political campaigns, employee performance evaluations and advertising strategies. [source] Practice and Forgetting Effects on Vocabulary Memory: An Activation-Based Model of the Spacing EffectCOGNITIVE SCIENCE - A MULTIDISCIPLINARY JOURNAL, Issue 4 2005Philip I. Pavlik Jr. Abstract An experiment was performed to investigate the effects of practice and spacing on retention of Japanese,English vocabulary paired associates. The relative benefit of spacing increased with increased practice and with longer retention intervals. Data were fitted with an activation-based memory model, which proposes that each time an item is practiced it receives an increment of strength but that these increments decay as a power function of time. The rate of decay for each presentation depended on the activation at the time of the presentation. This mechanism limits long-term benefits from further practice at higher levels of activation and produces the spacing effect and its observed interactions with practice and retention interval. The model was compared with another model of the spacing effect (Raaijmakers, 2003) and was fit to some results from the literature on spacing and memory. [source] | |||||||||||||