1,720,977 research outputs found
A neural mass model of place cell activity: theta phase precession, replay and imagination of never experienced paths
No full textRecent results on hippocampal place cells show that the replay of behavioral sequences does not simply reflect previously experienced trajectories, but may also occur in the reverse direction, or may even include never experienced paths. In order to elucidate the possible mechanisms at the basis of this phenomenon, we have developed a model of sequence learning. The present model consists of two layers of place cell units. Long-range connections among units implement heteroassociation between the two layers, trained with a temporal Hebb rule. The network was trained assuming that a virtual rat moves within a virtual maze. This training leads to the formation of bidirectional synapses between the two layers, i.e. synapses connecting a neuron both with its previous and subsequent element in the path. Subsequently, two distinct conditions were simulated with the trained network. During an exploratory phase, characterized by a similar consideration to the external environment and to the internal representation, the model simulates the occurrence of theta precession in the forward path and the temporal compression. During an imagination phase, when there is no consideration to the external location, the model produces trains of gamma oscillations, without the presence of a theta rhythm, and simulates the occurrence of both direct and reverse replay, and the imagination of never experienced paths. The new paths are built by combining bunches of previous trajectories. The main mechanisms at the basis of this behavior are explained in detail, and lines for future improvements (e.g., to simulate preplay) are discussed
Acoustical vision in patients with visual deficit: A neural network study
No full textPerception of external events relies on integration of different sensory information (multisensory integration). Multisensory integration is maximally beneficial when information from one sensory modality is impaired. Bimodal audiovisual stimulation has been shown to improve perception of visual events in patients with visual deficit due to a lesion in the primary visual cortex (hemianopia) or in higher-level fronto-parietal visual areas (neglect). Improvement was higher when auditory and visual stimuli were spatially coincident or at moderate spatial disparity, while no significant improvement was found at larger disparity. A neural network model, that includes the interaction between cortical areas and subcortical structures (the Superior Colliculus), is presented to investigate these phenomena in both kinds of patients. The model untangles the specific contribution of the circuits - spared by the lesion - that drive the emergence of visual perception under audiovisual stimulation, and interprets the dependence of the effect on audiovisual spatial disparity. The model extends our knowledge on the neural mechanisms subserving brain multisensory capabilities and how to take advantage of them for sensory loss compensation
Mathematical Models for Computational Neuroscience
No full textWe present the main aspects of mathematical models for computational neuroscience, with emphasis on the basic principles that can drive the construction of biologically inspired neural networks oriented to cognitive neuroscience problems. This chapter is subdivided into two distinct parts. In the first, the principal models of individual neural units (Hodgkin-Huxley, integrate and fire, and rate models) are described, together with a brief portrayal of synapse formalism. In the second, assuming rate models for simplicity, we summarize the peculiarities of important neural network typologies: associative networks (both hetero- and auto-association), self-organized networks, and error-correction networks (within the paradigm of reinforcement learning). For each network, simulation exempla are displayed and connections with physiological and pathological conditions of cognitive relevance are discussed. © 2014 Elsevier Inc. All rights reserved
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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