1,720,998 research outputs found
Impact of neuronal loss on relaxometry and magnetization transfer imaging estimations
No full textNo abstract availabl
Effect of voluntary repetitive long-lasting muscle contraction activity on the BOLD signal as assessed by optimal hemodynamic response function.
No full textAbstract
OBJECTIVE:
Among other neuroimaging techniques, functional magnetic resonance imaging (fMRI) can be useful for studying the development of motor fatigue. The aim of this study was to identify differences in cortical neuronal activation in nine subjects on three motor tasks: right-hand movement with minimum, maximum, and post-fatigue maximum finger flexion.
MATERIALS AND METHODS:
fMRI activation maps for each subject and during each condition were obtained by estimating the optimal model of the hemodynamic response function (HRF) out of four standard HRF models and an individual-based HRF model (ibHRF).
RESULTS:
ibHRF was selected as the optimal model in six out of nine subjects for minimum movement, in five out of nine for maximum movement, and in eight out of nine for post-fatigue maximum movement. As compared to maximum movement, a large reduction in the total number of active voxels (primary sensorimotor area, supplementary motor area and cerebellum) was observed in post-fatigue maximum movement.
CONCLUSION:
This is the first approach to the evaluation of long-lasting contraction effort in healthy subjects by means of the fMRI paradigm with the use of an individual-based hemodynamic response. The results may be relevant for defining a baseline in future studies on central fatigue in patients with neuropathological disorders
Alterazioni della connettività funzionale nel tremore essenziale (ET)
No full textnon disponibile; poster scientific
Cortical surface-in gradient of alterations in magnetization transfer imaging in association with CSF soluble factors
No full textNo abstract availabl
Can DTI and 3D-SHORE based indices differentiate RRMS from PMS Patients?
No full textMultiple Sclerosis (MS) is a long-lasting disease of the brain and spinal cord, characterized by demyelinating lesions in white matter (WM) as well as cortical lesions and tissue volume loss in several grey matter (GM) structures. Although GM alterations are a common feature of MS, they have not been largely explored in literature. Diffusion Tensor Imaging (DTI) is nowadays used to investigate the damaged WM structures in MS since DTI-based indices, as Fractional Anisotropy (FA) and Mean Diffusivity (MD), have been proven to reflect the pathological features of the disease in many studies. However, DTI has been scarcely employed for GM analysis plus is not able to model the complex fiber architecture. Hence, advanced models are required to probe the microstructural pathology. One of this, the Simple Harmonic Oscillator Based Reconstruction and Estimation (SHORE), is a novel diffusion-weighted Magnetic Resonance Imaging (dMRI) analysis method which is considered a promising tool to characterize tissue microstructure thanks to its ability to detect multiple diffusion directions. In this study, we aimed to probe the viability of DTI and 3D-SHORE derived indices for characterizing the microstructural GM modulations in Relapsing Remitting Multiple Sclerosis (RRMS) and Progressive Multiple Sclerosis (PMS) patients by relying on histogram-based analyses
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
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