1,721,245 research outputs found
Learning dynamics leading to persistent activity in recurrent networks of spiking neurons
Full text linkStefano Ferraina, Fabio Babiloni, Fabio Ferlazz
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
Use of a neural mass model for the analysis of effective connectivity among cortical regions based on high resolution EEG recordings
No full textAssessment of brain connectivity among different brain areas during cognitive or motor tasks is a crucial problem in neuroscience today. Aim of this work is to use a neural mass model to assess the effect of various connectivity patterns in cortical electroencephalogram (EEG) power spectral density, and investigate the possibility to derive connectivity circuits from EEG data. To this end, a model of an individual region of interest (ROI) has been built as the parallel arrangement of three populations, each described as in Wendling et al. (Eur J Neurosci 15:1499-1508, 2002). Connectivity among ROIs includes three parameters, which specify the strength of connection in the different frequency bands. The following main steps have been followed: (1) we analyzed how the power spectral density (PSD) is significantly modified by the kind of coupling hypothesized among the ROIs; (2) with the model, and using an automatic fitting procedure, we looked for a simple connectivity circuit able to reproduce PSD of cortical EEG in three ROIs during a finger-movement task. The estimated parameters represent the strength of connections among the ROIs in the different frequency bands. Cortical EEGs were computed with an inverse propagation algorithm, starting from measurement performed with 96 electrodes on the scalp. The present study suggests that the model can be used as a simulation tool, able to mimic the effect of connectivity on EEG. Moreover, it can be used to look for simple connectivity circuits, able to explain the main features of observed cortical PSD. These results may open new prospectives in the use of neurophysiological models, instead of empirical models, to assess effective connectivity from neuroimaging information
Brainshield: HREEG study of perceived pilot mental workload
No full textThe aim of the research project Brainshield is to investigate the possibility of predicting and documenting, through analysis of brain activity, the perceived pilot’s mental workload during each flight phase, specially with the occurrence of unusual or difficult attitudes. Pilot’s brain activity has been recorded and then analyzed by high resolution electroencephalography (HREEG) methodolgy. Mental workload indexes have been developed and then integrated with those derived from autonomics signals (electrocardiogram, eye blinks). At the end of each experimental session, pilots filled in the NASA-TLX test and an additional questionnaire specifically designed to obtain subjective ranks about difficulties faced off. The results presented might be congruent with the hypothesis that through brain signals analysis acquired from frontal, prefrontal and parietal brain sites it is possible to know cognitive status of a pilot during its operational flight activity. It has been proved how the relation between frontal theta activity synchronization and parietal alpha desynchronization is positively correlated with increasing of mental workload. The data showed an exhaustive overview of a pilot’s mental workload during the most difficult flight phases, providing important results for an industrial spin-off and opening to the possibility of a system development for the online mental workload monitoring, capable to give the pilots and the avionic system a feedback further enhancing the flight safety
A FLIGHT HISTORY FROM A COGNITIVE POINT OF VIEW: NOVICES VERSUS EXPERTS
No full textThe study presented in the following starts from the research of reliable indexes for monitoring the cognitive workload that the pilots face during flight missions besides the operational performances. In fact, the availability of such indexes should be an useful tool for the assessment of the spare cognitive capacity of the pilots during the flight, that is the available capacity for facing unexpected unusual attitudes or emergency situations. Those cerebral indicators could be used for the evaluation of the novice’s improvements during their pilot formation. Useful information and differences between a group of novice and expert military pilots, in terms of brain activity, have been found during flight simulations using those indexes. The experimental sessions consisted in simulated flights for unusual upset recovery training with the MB339 – alpha airplane. During the cruise phase have been also done experimental tests by the Brain Computer Interface (BCI) technology for the Silent Communication. The participants have been divided in two groups, the first one was of the Experts with a mean total flight hours of 1450 and 467 hours on the MB339 and the second one was of the Novices with a mean total flight hours of 157 and 36 hours on the MB339. Their brain activities were recorded and analyzed by the high resolution electroencephalography (HREEG). In addition, there have been recorded also the autonomic activities, as heart rate and eye blinks rate. Specific neurometric indexes have been defined for the correlation between the subjective workload assessment, by the NASA – TLX and a questionnaire for the difficulty evaluation, and the mental workload. At the end, the ANOVA statistical test has been done for evaluating the statistical significance. The results shown the existence of cognitive, emotional and performance differences between the novice and the expert pilots during the same flight activities. Brain and autonomic data were analyzed by defining specific indexes and then evaluating the variations in each phase of the flight simulation. The mean values of the workload index and of the heart rate of the novices were higher than those of the experts, showing that the novices’ workload was greater and that the experts were more relaxed during the simulated flight mission. Also, the mean value of the eye blinks rate was lower for the experts than for the novices, and this means that the first group paid more attention to what they were doing and to what happened in the surrounding environment. Confirmations of these facts have been found both from the analysis of the cortical maps, in which the novices’ cortical activity in different frequency bands was greater than the experts’ cortical activity, and from the mean total scores of the NASA – TLX and of the subjective difficulty evaluation. In this study it was possible to evaluate the usefulness of the workload index from the neurometric measures (EEG, blinks rate and heart rate) of military pilots. The results suggest the possibility to use benchmarks during the educational formation of the pilots for their performances evaluation with respect to specific reference values and parameters. In addition, it will be possible to adapt the educational flight programs in relation to the individual operational necessities, improving the organization of all the operational units and of the pilots’ training
Against smoking public service announcements, a neurometric evaluation of effectiveness
No full textTobacco causes more than 6 million of deaths per year [CDC website] use is the leading cause of preventable death and smoking-related illness worldwide. Research has shown that antismoking advertising may help reduce this habit [Bala et al. 2013]. Nowadays, public service announcements (PSAs) are considered “Effective” or “Ineffective” on the base of official reports concerning behavioral/attitudinal changes toward healthier patterns and health-related savings following the exposure to the PSA [e.g. Atusingwize et al. 2015]. Nevertheless, several studies suggest that the analysis of neurophysiologic signals variations in response to advertising can provide insights into subjects’ emotional and cognitive reaction to them [Astolfi et al. 2008, Vecchiato et al. 2011a, Vecchiato et al. 2011b, Cherubino et al. 2016]. In the present pilot study three neurometric indexes have been used for the evaluation of the efficacy of antismoking PSAs in a reduced sample of voluntary participants. The study applied the gathering of the electroencephalographic (EEG) rhythms variations, as well as the heart rate (HR) and galvanic skin response (GSR). The neurometric indicators here employed, previously used in several studies concerning TV commercials evaluation [Vecchiato et al. 2012, Vecchiato et al. 2014, Maglione et al. 2015], were: the Approach-Withdrawal (AW), the Effort (Eff) and the Emotional indexes (EI). ANOVA results suggested a significant higher values for AW , Effort and Emotional indexes (p=0,02; p= 0,03 and p= 0,01 respectively) related to the perception of the “Effective” antismoking PSA against the perception of the “Ineffective” one (Fig.1). Furthermore, behavioral data were collected, asking subjects, at the end of the recording session, to list all the advertisements they remember to have just watched. Subsequently they were asked to rate the advertisements they remembered assigning a score from 0 to 10. Behavioral results showed that 71.43% of the participants remembered the Effective PSA while only the 14.28% of the subjects remembered the Ineffective one. The Effective PSA reported an average score of 8±d.s.2.34 (with one subject rating the Effective PSA 4 and all the other subjects rating it between 8 and 10). The Ineffective PSA was remembered by 1 participant and the assigned rate was 5. A logistic regression analysis was then performed only between the Effective PSA recall values and each of the indexes; a statistical significance was reported for EI values (p=0.004), but not for the AW (p=0.19) or the Eff (p=0.76) indexes. Similarly, a correlation between rating scores of the Effective PSA and the estimated neurometric indexes values has been performed, but it didn’t reach the statistical significance: Eff (r=0.35), EI (r=0.09), AW (r=0.30). The sum the results here presented, support the observation that the neurometric approach to the study of anti-smoking PSAs revealed to be consistent with the classification of effectiveness based on behavioral and economic data. Since this is a pilot study, the results obtained need further investigation, in terms of enlarged stimuli sample and number of participants to provide indications concerning a possible neurometric pattern of the relevant features to be included in the realization of effective anti-smoking PSAs
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
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