1,721,002 research outputs found
Neuronal signature of spatial decision-making during navigation by freely moving rats by using calcium imaging
No full textSee the file "dataset_description.txt".Gobbo, Francesco; Mitchell-Heggs, Rufus; Tse, Dorothy; Spooner, Patrick A.; Schultz, Simon R.; Morris, Richard G. M.. (2022). Neuronal signature of spatial decision-making during navigation by freely moving rats by using calcium imaging, [dataset]. University of Edinburgh. Centre for Discovery Brain Sciences. https://doi.org/10.7488/ds/3774
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
Correlated Firing and the Information Represented By Neurons in Short Epochs
No full textIs the information transmitted by an ensemble of neurons determined solely by the number of spikes fired by each cell, or do correlations in the emission of action potentials also play a significant role? We derive a simple formula which enables this question to be answered rigorously for short timescales. Using a power series expansion, the mutual information the ensemble of neurons conveys about external stimuli is broken down into firing rate and correlation components. This analysis leads to a new quantification procedure which is directly applicable to simultaneous multiple neuron recordings. It also shows rigorously that even when noise correlations are not stimulus-modulated, synergistic effects can arise if signal and noise correlation are of opposite sign. Key words: correlations, synchronisation, synergy, redundancy 1 Introduction A controversy exists over the extent to which firing rates and correlations between the responses of different cells (such as synchronisation of ac..
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
An information-theoretic study of neuronal spike correlations in the mammalian cerebral cortex
Full text linkIn chapter I of this thesis we present a review of the historical background of the previousspike correlation studies and current state of the problem. In the chapters II, III and IV ofthis thesis we have applied an information theoretic approach to study the role of correlationsin the neuronal code, using the responses of pairs of neurons to drifting sinusoidal gratingsof different orientations and contrasts recorded in the primary visual cortex of anesthetizedmacaque monkeys. In chapter V we investigate the effects of a focal stroke in a populationof neurons on information transmission using a computational and analytical approach tothe problem. Finally, in chapter VI we use a novel analytical approach to study effects ofhigher order correlations in a population of neurons.It has been proposed in neuroscientific literature that pooling can lead to a significant improvementin signal reliability, provided that the neurons being pooled are at most weaklycross-correlated. We have computed mutual information, and compared the informationavailable from pairs of cells with the sum of the single cell information values. This allowedus to assess the degree of synergy (or conversely, redundancy) in the coding. In chapter IIof this thesis, we show that due to a loss of information encoded in the neuronal identity ofthe cells, pooling spikes across neurons leads to a loss of a large fraction of the informationpresent in their spike trains.We have used information theory to examine whether stimulus-dependent correlation couldcontribute to the neural coding of orientation and contrast by pairs of V1 cells. To this end,in chapter III, we have used a modified version of the method of information components.This analysis revealed that although synchrony is prevalent and informative, the additionalinformation it provides is frequently offset by the redundancy arising from the similar tuningproperties of the two cells. Thus, coding is roughly independent with weak synergy orredundancy arising depending on the similarity in tuning and the temporal precision of theanalysis. Our findings suggest that this would allow cortical circuits to enjoy the stabilityprovided by having similarly tuned neurons without suffering the penalty of redundancyas the associated information transmission deficit is compensated by stimulus dependentsynchrony.In chapter IV, we present a discussion about different measures of correlations and in particularwe propose the Jensen-Shannon Divergence as a measure of the distance between thecorresponding probability distribution functions associated with each spikes fired observedpatterns. We applied this Divergence for fixed stimuli as a measure of discrimination betweencorrelated and independent firing of pairs of cells in the primary visual cortex. Thisprovides a new, information-theoretic measure of the strength of correlation. We found thatthe relative Jensen-Shannon Divergence (measured in relation to the case in which all cellsfired completely independently) decreases with respect to the difference in orientation preferencebetween the receptive field from each pair of cells. Our finding indicates that theJensen-Shannon Divergence can be used for characterizing the effective circuitry network ina population of neurons.The underlying origins of synchronized firing between cortical neurons are still under discussion.Inter-cellular communication through chemically mediated synaptic transmissionis considered a major contributor to the formation of neuronal synchrony. GABAergic inhibitoryneurons may be involved in the generation of oscillatory activity in the cortex andits synchronization. Specifically, reduction of GABAergic inhibition may favour corticalplasticity producing functional recovery following focal brain lesions. Research into neurotransmittersystems is therefore of paramount importance to understand the origins ofsynchronized spiking. However, it is necessary to understand first how simple focal abnormalitiesin GABAergic modulators can affect the information transmission in an impairedbrain tissue. In chapter V, we present a computational and analytical model of a topographicallymapped population code which includes a focal lesion as well as a process for receptivefield enlargement (plasticity). The model simulates the recovery processes in the brain, andallows us to investigate mechanisms which increase the ability of the cortex to restore lostbrain functions. We have estimated the Fisher Information carried by the topographic mapbefore and after the stroke. Our finding shows that by tuning the receptive field plasticity toa certain value, the information transfer through the cortex after stroke can be optimized.A widespread distribution of neuronal activity can generate higher-order stochastic interactions.In this case, pair-wise correlations do not uniquely determine synchronizing spiking ina population of neurons, and higher order interactions across neurons cannot be disregarded.We present a new statistical approach, using the information geometry framework, for analyzingthe probability distribution function (PDF) of spike firing patterns by consideringhigher order correlations in a neuronal pool. In chapter VI, we have studied the limit ofa large population of neurons and associated a deformation parameter to the higher ordercorrelations in the PDF. We have also performed an analytical estimation of the Fisher informationin order to evaluate the implications of higher order correlations between spikeson information transmission. This leads to a new procedure to study higher order stochasticinteractions.The overall findings of this thesis warn about making any extensive statement about therole of neuronal spike correlations without considering the general case inclusive of higherorder correlations, and suggest a need to reshape the current debate about the role of spikecorrelations across neurons.PhD in Computational NeuroscienceImperial College LondonImperial College Londo
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