1,721,028 research outputs found
The central autonomic network at rest: Uncovering functional MRI correlates of time-varying autonomic outflow.
Full text linkPeripheral measures of autonomic nervous system (ANS) activity at rest have been extensively employed as putative biomarkers of autonomic cardiac control. However, a comprehensive characterization of the brain-based central autonomic network (CAN) sustaining cardiovascular oscillations at rest is missing, limiting the interpretability of these ANS measures as biomarkers of cardiac control. We evaluated combined cardiac and fMRI data from 34 healthy subjects from the Human Connectome Project to detect brain areas functionally linked to cardiovagal modulation at rest. Specifically, we combined voxel-wise fMRI analysis with instantaneous heartbeat and spectral estimates obtained from inhomogeneous linear point-process models. We found exclusively negative associations between cardiac parasympathetic activity at rest and a widespread network including bilateral anterior insulae, right dorsal middle and left posterior insula, right parietal operculum, bilateral medial dorsal and ventrolateral posterior thalamic nuclei, anterior and posterior mid-cingulate cortex, medial frontal gyrus/pre-supplementary motor area. Conversely, we found only positive associations between instantaneous heart rate and brain activity in areas including frontopolar cortex, dorsomedial prefrontal cortex, anterior, middle and posterior cingulate cortices, superior frontal gyrus, and precuneus. Taken together, our data suggests a much wider involvement of diverse brain areas in the CAN at rest than previously thought, which could reflect a differential (both spatially and directionally) CAN activation according to the underlying task. Our insight into CAN activity at rest also allows the investigation of its impairment in clinical populations in which task-based fMRI is difficult to obtain (e.g., comatose patients or infants)
Effects of Respiratory-Gated Auricular Vagal Afferent Nerve Stimulation (RAVANS) in Hypertensive Patients during the Handgrip experiment
No full textSeveral studies have proposed transcutaneous stimulation of the auricular branch of the vagus nerve (ABVN) as a non-invasive alternative to vagus nerve stimulation (VNS). In this study we present preliminary results of the effect of respiratory-gated, auricular vagal afferent nerve stimulation (RAVANS) associated with a Handgrip (HG) experiment. Twelve hypertensive subjects underwent three experimental sessions on non-consecutive days. In each session subjects performed HG before and after receiving one of three types of RAVANS stimulation in a counterbalanced order: low-intensity, medium-intensity or sham stimulation. Electrocardiogram recordings were collected and analyzed by point process linear analysis of heartbeat dynamics, and instantaneous time- and frequency-domain features of heart rate variability were estimated. Results provide a preliminary characterization of HG elicited autonomic responses before and after different RAVANS stimulation intensities
Assessing regional cerebral blood flow contributions to the [11C]PBR28 PET signal in chronic pain patients.
No full textAcute Effects of Respiratory-Gated Auricular Vagal Afferent Nerve Stimulation (RAVANS) in the Modulation of Blood Pressure in Hypertensive Patients
No full textIn this study, we evaluate the acute effects of a novel, non-invasive, respiratory-gated auricular vagal afferent nerve stimulation (RAVANS) technique on arterial blood pressure levels in hypertensive patients. We consider data from 18 hypertensive subjects (53.6±6.3 years, 9 males) during three stimulation sessions where they received either sham, low-intensity, or medium-intensity stimulation in randomized order. Blood pressure was continuously collected during 15-minute baseline, stimulation, and recovery windows. Our statistical analysis shows that the percent decrease of median systolic blood pressure from baseline was significantly higher during RAVANS (medium-intensity) when compared to sham. Furthermore, a two-way ANOVA reveals a significant interaction between Intervention and Phase for changes in median systolic blood pressure. Post hoc testing reveals that this effect was driven by the Recovery Phase following RAVANS where median Systolic blood pressure significantly decreased in the last 5 minutes compared to sham. Our results indicate that exhalatory-gated RAVANS has acute modulatory effects on systolic blood pressure levels of hypertensive patients. Further longitudinal studies will be required to evaluate the therapeutic potential of the RAVANS electroceutical device
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
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