1,721,059 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
Mood-related Differences in Cerebral Blood Flow in Adolescents with Bipolar Disorder
Full text linkNumerous adult bipolar disorder (BD) studies have examined cerebral blood flow (CBF) in relation to mood, whereas little is known on this topic in adolescents. We enrolled 129 adolescents (mean age 17.34+/-1.42 years), including 72 BD (28 hypomanic/mixed, 19 depressed, 25 euthymic) and 57 healthy controls (HC). Pseudocontinuous arterial spin labeling (ASL) magnetic resonance imaging (MRI) evaluated CBF, using both a region of interest and whole brain voxel-wise approach. Within-BD analysis examined the association of mania and depression severity with CBF. We found differences in terms of CBF between groups with higher CBF in the BD euthymic group than in HC and symptomatic BD in temporal, precentral, and occipital regions. Severity of depressive symptoms in BD was negatively correlated with CBF in the anterior cingulate cortex and temporal regions. Higher CBF in euthymic BD adolescents may reflect developmentally-specific compensatory CBF regulation mechanisms required to maintain euthymia.M.Sc
Mood-related Differences in Cerebral Blood Flow in Adolescents with Bipolar Disorder
No full textNumerous adult bipolar disorder (BD) studies have examined cerebral blood flow (CBF) in relation to mood, whereas little is known on this topic in adolescents. We enrolled 129 adolescents (mean age 17.34+/-1.42 years), including 72 BD (28 hypomanic/mixed, 19 depressed, 25 euthymic) and 57 healthy controls (HC). Pseudocontinuous arterial spin labeling (ASL) magnetic resonance imaging (MRI) evaluated CBF, using both a region of interest and whole brain voxel-wise approach. Within-BD analysis examined the association of mania and depression severity with CBF. We found differences in terms of CBF between groups with higher CBF in the BD euthymic group than in HC and symptomatic BD in temporal, precentral, and occipital regions. Severity of depressive symptoms in BD was negatively correlated with CBF in the anterior cingulate cortex and temporal regions. Higher CBF in euthymic BD adolescents may reflect developmentally-specific compensatory CBF regulation mechanisms required to maintain euthymia.M.Sc
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
Neurostructural Correlates of Body Mass Index & Waist Circumference in Adolescents with Bipolar Disorder
Full text linkObesity among youth with bipolar disorder (BD) is associated with greater illness severity. In adult BD, obesity is associated with neurostructural differences. We examined this topic for the first time in youth. T1-weighted images of 40 BD and 48 psychiatrically healthy controls (HC) were processed using FreeSurfer to derive cortical region of interest (ROI) volumes/cortical thickness for frontal lobe (FL), prefrontal cortex (PFC), and orbitofrontal cortex (OFC), as well as subcortical ROI volumes for amygdala and hippocampus. Our results show that there was a significant BMI-by-group interaction effect on FL and OFC volumes. In the BD group only, BMI was significantly negatively associated with OFC volume, as well as FL, OFC, and PFC cortical thickness. Our results suggest that elevated BMI is associated with neurostructural changes in youth with BD but not in HC. Treatment studies examining the effect of optimizing weight on brain structure in BD are warranted.M.Sc
Examining Brain and Body Correlates of Cerebrovascular Reactivity Among Adolescents with and without Bipolar Disorder
Full text linkCardiovascular disease (CVD) is excessive and premature among individuals with bipolar disorder (BD). Cerebrovascular reactivity (CVR), a marker of cerebrovascular health, is the capacity of the brainâ s blood vessels to vasodilate when induced by vasoactive substances. We examined this topic for the first time in BD. CVR was measured in 25 adolescents with BD and 25 age and sex-matched psychiatrically healthy controls (HCs). Whole-brain analyses showed that BDs have lower CVR in the posterior cingulate gyrus and periventricular white matter. When controlling for differences in body mass index (BMI), additional between group CVR differences were observed in the temporal poles, supramarginal gyrus and lingual gyrus. There were no significant clusters of the brain that were BD>HC. Our results suggest that CVR may be a proxy for future risk of CVD and/or cerebrovascular disease, given the location of anomalous CVR within regions where cerebrovascular pathology occurs in mid-life.M.Sc
Neurostructural and Neurovascular Correlates of Retinal Vascular Caliber in Adolescents with Bipolar Disorder
Full text linkBipolar disorder (BD) is recognized by the American Heart Association as a condition that predisposes youth to early-onset cardiovascular disease. The magnitude of this prematurity cannot be attributed to lifestyle or traditional cardiovascular risk factors alone. Early evidence suggests that microvascular structure and function may be impaired early in the course of BD. The extent to which vascular measures are related to brain structure and function in BD is not well-understood, despite the potential benefits of focusing on the vascular-brain interface in BD. This thesis examines the association of retinal vascular caliber, a proxy cerebrovascular measure, with brain structure, cerebral blood flow (CBF), and white matter integrity in adolescents with BD. We hypothesized that better retinal vascular caliber (i.e., higher arteriovenous ratio) would be associated with more positive neuroimaging phenotypes in adolescents with BD.All participants completed retinal fundus imaging, from which the central retinal arteriolar equivalent (CRAE) and the central retinal venular equivalent (CRVE) were measured. Arteriovenous ratio (AVR), a proxy measure of cardiovascular risk, was computed as a ratio of the two. All participants underwent 3D T1-weighted structural, arterial-spin labelling, and diffusion weighted magnetic resonance imaging (MRI). For each objective, retinal arteriolar caliber was higher in adolescents with BD relative to controls after adjusting for age, sex, and tobacco smoking. In the overall sample, arteriolar caliber was negatively associated with anterior cingulate cortex (ACC) volume and surface area, and with corpus callosum and forceps minor fractional anisotropy (FA). In the BD group, higher AVR was associated with greater ACC CBF, although this trend was not observed in controls. Finally, there were several diagnosis-by-retinal interaction effects on brain structure and FA, such that higher AVR was more negatively associated with regional brain structure and higher venular caliber was more positively associated with FA, in BD relative to controls.
Findings from this thesis are proof-of-concept, insofar as microvascular readouts are relevant to brain health in youth. The clinical implications of these findings are likely accentuated in adolescents with BD. Overall, these results suggest that optimizing cardiovascular health may offer unique benefits from both a heart and a brain perspective.Ph.D.2023-11-11 00:00:0
Neurostructural, Neurofunctional, and Neurocognitive Phenotypes of Self-harm among Youth with Bipolar Disorder
Full text linkYouth with bipolar disorder (BD) are at greatly elevated risk for suicide. Self-harm, regardless of suicidal intent, is a leading risk factor for suicide. Given the paucity of research to date, we examined neurostructural, neurofunctional, and neurocognitive phenotypes in relation to self-harm among youth with BD. It was hypothesized that youth with a history of self-harm would have altered brain structure, functional connectivity, and poorer decision-making performance. Each of the three projects in this thesis included the following groups of participants, ages 13-20 years old: BD youth with history of self-harm (BDSH+), BD youth without history of self-harm (BDSH-), and healthy controls (HC). Neurostructural analyses examined 3T MRI measures of cortical thickness, surface area (SA), and volume, combining region-of-interest and vertex-wise approaches. Resting-state functional connectivity analyses used a seed-to-voxel approach. Neurocognition analyses focused on reward-related decision-making and risk-taking performance on an automated computerized test battery.
In neurostructural vertex-wise analyses, BDSH+ had lower SA in the precentral and inferior temporal gyri, and lower caudal middle frontal gyrus volume compared to BDSH- and HC youth. In functional connectivity analyses, BDSH- had increased positive connectivity between the amygdala and occipital cortex, and between the dorsolateral prefrontal cortex and frontal pole, compared to BDSH+ and HC; and BDSH+ had increased positive connectivity between orbitofrontal cortex and precuneus compared to BDSH- and HC. In neurocognitive analyses, there was a difference in the overall proportion of points bet, such that BDSH- performed better than both BDSH+ and HC youth. Mean latency was also significant with BDSH- deliberating longer than HC youth. Risk-taking was different between groups, with BDSH- showing greater self-control compared to both BDSH+ and HC youth.
Self-harm in youth with BD is associated with smaller neurostructural measures and altered connectivity in reward-related regions. In addition, youth with BD and no history of self-harm had greater self-control and lower risk-taking. We speculate this may be reflective of a compensatory process among BDSH- serving a protective role in suicide risk. These findings provide evidence of neurobiological phenotypes associated with self-harm among youth with BD, which may help refine suicide prediction and inform clinical trial designs.Ph.D.2023-11-11 00:00:0
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