1,720,986 research outputs found
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
Long-Term Consequences of Early Eye Enucleation on Audiovisual Processing
Full text linkA growing body of research shows that complete deprivation of the visual system from the loss of both eyes early in life results in changes in the remaining senses. Is the adaptive plasticity observed in the remaining intact senses also found in response to partial sensory deprivation specifically, the loss of one eye early in life? My dissertation examines evidence of adaptive plasticity following the loss of one eye (unilateral enucleation) early in life. Unilateral eye enucleation is a unique model for examining the consequences of the loss of binocularity since the brain is completely deprived of all visual input from that eye. My dissertation expands our understanding of the long-term effects of losing one eye early in life on the development of audiovisual processing both behaviourally and in terms of the underlying neural representation. The over-arching goal is to better understand neural plasticity as a result of sensory deprivation. To achieve this I conducted seven experiments, divided into 5 experimental chapters, that focus on the behavioural and structural correlates of audiovisual perception in a unique group of adults who lost one eye in the first few years of life. Behavioural data (Chapters II-V) in conjunction with neuroimaging data (Chapter VI) relate structure and function of the auditory, visual and audiovisual systems in this rare patient group allowing a more refined understanding of cross sensory effects of early sensory deprivation. This information contributes to us better understanding how audiovisual information is experienced by people with one eye. This group can be used as a model to learn how to accommodate and maintain the health of less extreme forms of visual deprivation and to promote overall long-term visual health
Altered White Matter Structure in Adults Following Early Monocular Enucleation
Full text linkVisual deprivation from early monocular enucleation (the surgical removal of one eye) results in a number of long-term behavioural and morphological adaptations in the visual, auditory, and multisensory systems. This thesis aims to investigate how the loss of one eye early in life affects structural connectivity within the brain. A combination of diffusion tensor imaging and tractography was used to examine structural differences in 18 tracts throughout the brain of adult participants who had undergone early monocular enucleation compared to binocularly intact controls. We report significant structural changes to white matter in early monocular enucleation participants that extend beyond the primary visual pathway to include interhemispheric, auditory and multisensory tracts, as well as several long association fibres. Overall these results suggest that early monocular enucleation has long-term effects on white matter structure throughout the brain
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
Sex and Sexual Orientation Differences in Perceptual and Cognitive Processing
Full text linkSex differences have been found in some visual perception and cognitive abilities, and male and female brains have been shown to have differences in functional activation. These abilities include mental rotation, face recognition and face detection. One way to measure mental rotation is by using the mental rotation task (MRT), with males outperforming females (Voyer, 2011). Face perception tasks show differences favouring females (McBain et al., 2009; Brewster et al., 2012). Same-sex attracted males tend to perform at the level of females in face recognition ability (Brewster et al., 2012). This thesis seeks to further examine the effect sexual orientation has on these visual and perceptual abilities that have previously shown sex differences. A male advantage was found for mental rotation ability, with heterosexual males outperforming heterosexual females. Within the same-sex attracted groups, this difference was not found, with same-sex attracted females performing at the level of same-sex attracted males
The Effects of Theta Burst Stimulation to the Occipital Cortex on Brain Biomarkers Measured by Magnetic Resonance Spectroscopy
Full text linkTheta burst stimulation (TBS), a type of transcranial magnetic stimulation (TMS), uses repeated high-frequency bursts to induce neural noise in the cortex. An intermittent TBS (iTBS) protocol is generally considered excitatory, while continuous TBS (cTBS) is generally considered inhibitory. TBS effects are highly variable and have been primarily studied in the primary motor cortex (M1). We investigated the effects of iTBS and cTBS to the primary visual cortex (V1) on occipital Glx (glutamate and glutamine composite) and GABA+ (gamma-aminobutyric acid and macromolecules composite) concentrations compared to sham stimulation. Thirty participants received a single session of individual stereotaxically-guided TBS to the V1. Participants received either cTBS, iTBS or sham TBS. GABA+ and Glx were measured at the stimulation site using magnetic resonance spectroscopy. Baseline pre-TBS GABA+ and Glx levels were compared to those immediately post- and one hour post-TBS. The results show a trend for a decrease in GABA+ immediately following cTBS compared to one hour post-TBS and a trend for an increase in Glx immediately following iTBS compared to one hour-post TBS. There was also an increase in GABA+ from baseline to one hour-post TBS and a trend for an increase in GABA+ and Glx composite ratio levels following sham. Since there was a lack of systematic trends in the data, we suspect there is no relevant change from a single session of TBS to neurotransmitter levels in the V1. Perhaps, only repeated application of TBS may lead to substantial benefits. This indicates that a single session of TBS can be used safely in the laboratory without effects on neurotransmitter levels in the V1
Development of Low-Frequency Repetitive Transcranial Magnetic Stimulation as a Tool to Modulate Visual Disorders: Insights from Neuroimaging
Full text linkRepetitive transcranial magnetic stimulation (rTMS) has become a popular neuromodulation technique, increasingly employed to manage several neurological and psychological conditions. Despite its popular use, the underlying mechanisms of rTMS remain largely unknown, particularly at the visual cortex. Moreover, the application of rTMS to modulate visual-related disorders is under-investigated. The goal of the present research was to address these issues. I employ a multitude of neuroimaging techniques to gain further insight into neural mechanisms underlying low-frequency (1 Hz) rTMS to the visual cortex. In addition, I begin to develop and refine clinical low-frequency rTMS protocols applicable to visual disorders as an alternative therapy where other treatment options are unsuccessful or where there are simply no existing therapies. One such visual disorder that can benefit from rTMS treatment is the perception of visual hallucinations that can occur following visual pathway damage in otherwise cognitively healthy individuals. In Chapters 23, I investigate the potential of multiday low-frequency rTMS to the visual cortex to alleviate continuous and disruptive visual hallucinations consequent to occipital injury. Combining rTMS with magnetic resonance imaging techniques reveals functional and structural cortical changes that lead to the perception of visual hallucinations; and rTMS successfully attenuates these anomalous visual perceptions. In Chapters 45, I compare the effects of alternative doses of low-frequency rTMS to the visual cortex on neurotransmitter levels and intrinsic functional connectivity to gain insight into rTMS mechanisms and establish the most effective protocol. Differential dose-dependent effects are observed on neurotransmitter levels and functional connectivity that suggest the choice of protocol critically depends on the neurophysiological target. Collectively, this work provides a basic framework for the use of low-frequency rTMS and neuroimaging in clinical application for visual disorders
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