1,720,970 research outputs found
Multimodal imaging of the amygdala in non-clinical subjects with high vs. low autistic-like social skills traits
Full text linkRecent clinical and theoretical frameworks suggest that social skills and theory of mind impairments characteristic of autism spectrum disorder (ASD) are distributed in the general population on a continuum between healthy individuals and patients. The present multimodal study aimed at investigating the amygdala's function, perfusion, and volume in 56 non-clinical subjects from the general population with high (n = 28 High-SOC) or low (n = 28 Low-SOC) autistic-like social skills traits. Participants underwent magnetic resonance imaging to evaluate the amygdala's functional connectivity at rest, blood perfusion by means of arterial spin labelling, its activation during a face evaluation task and lastly grey matter volumes. The High-SOC group was characterised by higher blood perfusion in both amygdalae, lower volume of the left amygdala and higher activations of the right amygdala during processing of human faces with fearful value. Resting state analyses did not reveal any significant difference between the two groups. Overall, our results highlight the presence of overlapping morpho-functional alterations of the amygdala between healthy individuals and ASD patients confirming the importance of the amygdala in this disorder and in social and emotional processing. Our findings may help disentangle the neurobiological facets of ASD elucidating aetiology and the relationship between clinical symptomatology and neurobiology
Dimensions of psychosis: Elucidating the subclinical spectrum using neuroimaging markers
No full textPsychosis unifies a collective of disorders characterised by symptom dimensions (Gaebel & Zielasek, 2015). Purposefully delimited clinical descriptors of schizophrenia spectrum and psychotic disorders (American Psychiatric Association, 2013) impose challenges on the identification of aetiological and clinically meaningful predictors. The disassembly of psychiatric diagnoses into their elementary symptom dimensions has helped formulate psychosis phenotypes fitted on a psychosis continuum (Verdoux & van Os, 2002). Aetiological models of psychosis may be studied through schizotypy and transient psychotic experiences (Barrantes-Vidal et al., 2015; Nelson, Fusar-Poli, & Yung, 2012), collectively termed subclinical psychosis phenotypes. The dimensional psychometric structures of these phenotypes varying in temporal stability (Linscott & van Os, 2013; Mason et al., 1995; Stefanis et al., 2002), and their implications might be further consolidated when paired with neuroimaging parameters (Siever & Davis, 2004).
Three neuroimaging studies aimed to examine the relationship between subclinical psychotic phenotypes and neurobiology. Surface and volume-based morphometric (VBM) methods were implemented to examine the variety of cortical and subcortical signatures of different phenotype dimensions. Study 1 investigated whether cortical surface gyrification -a maker of genetic and developmental influences on cortical morphology (Docherty et al., 2015; Haukvik et al., 2012)- is associated with dimensional psychosis prone phenomena (Konings, Bak, Hanssen, van Os, & Krabbendam, 2006; Stefanis et al., 2002). Early cortical organisation contributes to cognitive capacities in later life (Gautam et al., 2015; Gregory et al., 2016; Papini et al., 2020). Given that cognitive deficits are present in psychosis prone and clinical samples to varying extents (Hou et al., 2016; Siddi et al., 2017), Study 1 also explored the mediating role of cognition (both as a general measure and intelligence quotient) as a psychosis endophenotype in the relationship between regional gyrification and PLE distress. Study 2 and Study 3 used VBM to investigate structural brain correlates for psychotic-like experiences (PLE) and trait psychosis phenotypes (schizotypy). Different PLE facets (quantity and distress severity) (Hanssen, Bak, et al., 2005; Ising et al., 2012) were used to estimate whole-brain grey matter volume, followed by interaction models in subsequent prefrontal regions of interest (Study 2). The medial temporal lobe includes the hippocampal subfields, which are regions of interest in psychosis pathophysiology (Lieberman et al., 2018; Mathew et al., 2014; Schobel et al., 2013). Based on a previous study in schizoytypy (Sahakyan et al., 2020), Study 3 examined the relationship between schizotypal trait dimensions (Mason et al., 1995) and PLE, and their interactions, and hippocampal subfields and the amygdala.
The results of Study 1 showed that psychometrically assessed PLE were associated with reduced gyrification in parietal and temporal regions, indicating that psychosis proneness correlates with neurodevelopmental factors (Fonville et al., 2019; Liu et al., 2016). A lack of mediating pathways between regional gyrification and PLE suggested that cognition effects may emerge in larger samples (Mollon et al., 2016) and/or increasingly psychosis pone phenotypes. Elaborating on the distinction between PLE quantity versus distress, Study 2 showed that PLE load, but not distress severity, were associated with volume increases in prefrontal and occipitotemporal regions. At increased distress severity for perceptual abnormalities, PLE were associated with regional volume reductions of the superior frontal gyrus. Study 3 showed differential relationships between schizotypy dimensions and volumes of the MTL that are involved in the pathophysiology of schizophrenia. PLE per se did not associate with amygdala or hippocampal subfield volumes, but a positive association between the hippocampal subiculum and PLE was moderated by positive schizotypy. Study 3 underscored the enhanced usefulness of schizotypy as an endophenotype in psychosis research when its multidimensional organisation (Grant, 2015; Vollema & van den Bosch, 1995) is respected.
The results support the use of psychosis symptom dimensions, showing different (positive and negative) neuroanatomical associations. While case-control studies in schizophrenia show consistent volume reductions of the prefrontal and temporal cortices (Haijma et al., 2013; Honea, Crow, Passingham, & Mackay, 2005), these findings contribute to more heterogeneous volumetric relationships in nonclinical individuals. Reduced regional cortical gyrification proposes a continuous distribution of neurodevelopmental impacts. Distress severity and schizotypy occasioned modulatory effects in prefrontal and hippocampal subfield volumes, respectively. Collectively, these three cross-sectional studies extend previous research suggesting that dimensional phenotypes show neuroanatomical variation supportive of a psychosis continuum possibly characterised by an underlying non-linearity (Bartholomeusz et al., 2017; Binbay et al., 2012; Johns & van Os, 2001).Unter dem Sammelbegriff der Psychosen versteht sich eine Gruppe von Störungen mit vielfältigen Symptomen (Gaebel & Zielasek, 2015). Fall-Kontroll-Studien untersuchen anhand kategorialer Diagnosen (American Psychiatric Association, 2013) neurobiologische Veränderungen einhergehend mit psychotischen Erkrankungen. Im dimensionalen Krankheitsverständnis beruht die Bezeichnung klinischer Phänotypen auf der Annahme eines Kontinuums unterschiedlicher Symptome (Stefanis et al., 2002; Verdoux & van Os, 2002). Dieser dimensionale Ansatz kann das Auftreten psychotischer Merkmale bei Gesunden erklären und gleichzeitig zur erweiterten Erforschung ätiologischer Modelle genutzt werden (Barrantes-Vidal et al., 2015; Nelson et al., 2012). Zu den subklinischen Phänotypen gehören einerseits stabile Merkmale wie schizotype Traits (Mason et al., 1995), so wie vermeintlich transiente psychose-nahe Erlebnisse (Linscott & van Os, 2013; Stefanis et al., 2002). Mittels hirnmorphometrischer Methoden können neuroanatomische Parallelen und Abgrenzungen zu den klinischen Krankheitsbildern untersucht werden (Nenadić, Lorenz, et al., 2015; Siever & Davis, 2004; Taylor et al., 2020).
Drei Querschnittstudien untersuchten mögliche Zusammenhänge zwischen psychometrisch erfassten subklinischen Psychose-Phänotypen und der kortikalen Struktur. Studie 1 widmete sich der Analyse der kortikalen Oberflächengyrierung, welche einen Indikator für die frühe kortikale Entwicklung in Abhängigkeit von genetischen und Entwicklungsfaktoren (Docherty et al., 2015; Haukvik et al., 2012) darstellt. Diese wurde im Zusammenhang mit dimensionalen psychose-nahen Erlebnissen untersucht. Die kortikale Faltung erklärt auch spätere kognitive Leistungen (Gautam et al., 2015; Hedderich et al., 2019; Papini et al., 2020), welche bei PatientInnen, Hoch-Risiko Phänotypen und Gesunden mit einem familiären Psychoserisiko Verschlechterungen aufweisen (Hou et al., 2016; Siddi et al., 2017). Anhand von Mediationsmodellen wurde der Einfluss neurokognitiver Funktionen auf den Zusammenhang zwischen regionaler Gyrifizierung und psychose-nahen Erlebnissen untersucht. Studien 2 und 3 untersuchten hirnstrukturelle Korrelate anhand von Voxel-basierter Morphometrie. Studie 3 verfolgte das Ziel, sowohl die Ausprägung als auch die Facette des entstandenen Belastungsgrades durch subklinische Erlebnisse (Hanssen, Bak, et al., 2005; Ising et al., 2012) auf der hirnstrukturellen Ebene abzubilden. Die Auswirkung des Zusammenspiels dieser beiden Facetten (Ausprägung und dimensionsspezifische Belastung) auf die Struktur präfrontaler Areale wurde mit Moderationsanalysen untersucht. Basierend auf bestehenden Ergebnissen zur Reduktion hippocampaler Volumina in den frühen und späten Stadien psychotischer Erkrankungen (Lieberman et al., 2018; Mathew et al., 2014; Schobel et al., 2013), sowie bei der Schizotypie Gesunder (Sahakyan et al., 2020), untersuchte Studie 3 die medial temporalen Strukturen. Es wurden die Zusammenhänge zwischen unterschiedlichen Schizotypie-Dimensionen und subklinischen psychose-nahen Erlebnissen, sowie deren Interaktion, mit den Volumina einzelner hippocampaler Teilvolumina und der Amygdala untersucht.
Die Ergebnisse zeigten unterschiedliche regionale oberflächenbasierte Korrelate der kortikalen Faltung in Abhängigkeit von der Merkmalsdimension. Reduktionen der kortikalen Gyrierung in parietalen und temporalen Bereichen stimmten mit den Regionen neuroanatomischer Veränderungen aus klinischen Studien bei Schizophrenie-PatientInnen überein. Der Effekt der Gyrierung auf die Ausprägung subklinischer Phänotypen in diesen und präfrontalen Bereichen wurde jedoch nicht durch die kognitive Leistung vermittelt. Studie 2 zeigte, dass die Ausprägung des subklinischen Phänotyps, jedoch nicht die mit solchen Erlebnissen verbundene Belastung, mit einer Zunahme der grauen Substanz in präfrontalen und okzipitotemporalen Arealen assoziiert waren. Eine Volumenreduktion im Gyrus frontalis superior wurde durch die Interaktion der subklinischen Phänotyp Ausprägung mit der Belastung durch perzeptuelle Merkmale bedingt. Hinsichtlich der Assoziationen in den medial temporalen Strukturen konnte gezeigt werden, dass strukturelle Variation der Amgygdala und einzelner hippocampaler Teilvolumina eher durch stabile schizotype Traits, als durch psychose-nahe Erlebnisse, erklärt wird. Im hippocampalen Subiculum moderierte positive Schizotypie jedoch den Zusammenhang zwischen transienten Erlebnissen und Volumenzunahme. Somit hebt Studie 3 die besondere Rolle stabiler Endophänotypen (Barrantes-Vidal et al., 2015) sowie die Berücksichtigung der Dimensionalität subklinischer Phänotypen (Grant, 2015; Vollema & van den Bosch, 1995) im Psychosespektrum hervor.
Die Ergebnisse der drei Studien unterstützen den dimensionalen Ansatz, bei dem unterschiedliche psychotische Merkmale im Einzelnen untersucht werden. Diese psychose-nahen Erlebnisse wiesen bei Gesunden kortikale Assoziationen in psychose-relevanten präfrontalen und temporalen Arealen auf (Haijma et al., 2013; Honea et al., 2005), welche jedoch im Gegensatz zu klinischen Befunden heterogenere Beziehungen aufweisen. Im subklinischen Bereich ließen sich zudem Abweichungen der kortikalen Faltung feststellen (Fonville et al., 2019; Liu et al., 2016), welche einen kontinuierlichen Zusammenhang mit entwicklungsbedingten Faktoren erkennen lassen. Die modifizierenden Eigenschaften von schizotypen Traits und der Belastung durch perzeptuelle Auffälligkeiten auf jeweils positive und negative Zusammenhänge in hippocampalen und präfrontalen Strukturen deuten darauf hin, dass innerhalb des Psychose-Kontinuum möglichweise nichtlineare kortikale Veränderungen stattfinden (Bartholomeusz et al., 2017; Binbay et al., 2012; Johns & van Os, 2001)
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
