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Novel functional imaging approaches for investigating brain plasticity in multiple sclerosis and Parkinson’s disease: from research to clinical applications
No full textNeuronal plasticity, as the capacity of the brain to respond to external demands or to injury, has emerged as a crucial mechanism to preserve, at least in part, an adequate behavioral functioning after an injury and as the process underlying improvements in disability during rehabilitation. Brain plasticity can be detected with both structural and functional magnetic resonance imaging and more and more processing techniques have been developed to better capture the occurring changes and to better define the potential plasticity. Gait and balance are affected in patients with multiple sclerosis since the early stages of the disease with sensory deficits playing a major role in determining both balance and gait impairment. Moreover, gait disorders are one of the major causes of disability in patients with Parkinson’s disease, in particular if suffering from freezing of gait. With this work we aimed at i) investigating the functional reorganization occurring in multiple sclerosis at both early and late stages of the disease, ii) characterizing the functional pattern underlying sensory impairment in patients with early multiple sclerosis and iii) verifying the neural correlates of action observation of gait in patients with Parkinson’s disease. These different studies fit into a larger framework where neuroimaging techniques, in particular functional imaging, would support the clinicians in identifying tailored rehabilitation treatments and the patients who would better benefit from them. We found that patients with early multiple sclerosis showed a higher brain functional flexibility, expressed in terms of blood oxygen level dependent signal variability, which correlated to clinical disability, representing a possible compensatory mechanism. In patients with early multiple sclerosis we also observed subtle position sense deficits, not detectable with a standard neurological examination, and which affected still standing balance. Moreover, these deficits were related to a structural damage at the level of the corpus callosum and to functional activity patterns mainly involving the frontoparietal regions. On the contrary, patients with multiple sclerosis at the progressive stages presented with more subtle changes in the resting state functional connectivity which, nonetheless, were related to clinical disability. Lastly, the presence of freezing of gait in patients with Parkinson disease influenced the neural activation underpinning the action observation of walking. Altogether, these results offer an better insight into the pathophysiological mechanisms underlying disability in patients with multiple sclerosis and constitute a groundwork for the enhancement of rehabilitation protocols to improve gait and balance in both multiple sclerosis and Parkinson’s disease, supporting the embracing of new strategies such as sensory integration and action observation training
Monitoring Progressive Multiple Sclerosis with Novel Imaging Techniques
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A Multimodal Imaging Approach Demonstrates Reduced Midbrain Functional Network Connectivity Is Associated With Freezing of Gait in Parkinson's Disease
No full textThe role of disconnection in explaining disability in multiple sclerosis
No full textBACKGROUND: In multiple sclerosis, the correlation between white matter lesion volumes (LV) and expanded disability status scale (EDSS) is at best moderate, leading to the “clinico-radiological paradox”, influenced by many factors, including the lack of information on the spatial localisation of each lesion on synthetic metrics such as LV. We used a probabilistic approach to provide the volume of WM tracts that may be disconnected by lesions and to evaluate its correlation with EDSS. METHODS: Forty-five patients (aged 37.4 ± 6.8 years, mean ± standard deviation; 30 females; 29 relapsing-remitting, 16 progressive) underwent 3-T magnetic resonance imaging. Both LV and the volume of the tracts crossing the lesioned regions (disconnectome volume, DV) were calculated using BCBtoolkit and correlated with EDSS. RESULTS: T1-weighted LV and DV significantly correlated with EDSS (p ≤ 0.006 r ≥ 0.413) as it was for T2-weighted LV and T2-weighted DV (p ≤ 0.004 r ≥ 0.430), but only T1-weighetd and T2-weighted DVs were EDSS significant predictors (p ≤ 0.001). The correlations of T1-weighted and T2-weighted LV with EDSS were significantly mediated by DV, while no effect of LV on the EDSS-DV correlation was observed. CONCLUSION: The volume of disconnected WM bundles mediates the LV-EDSS correlation, representing the lonely EDSS predictor
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
Cerebellum and neurodegenerative diseases: Beyond conventional magnetic resonance imaging
Full text linkThe cerebellum plays a key role in movement control and in cognition and cerebellar involvement is described in several neurodegenerative diseases. While conventional magnetic resonance imaging (MRI) is widely used for brain and cerebellar morphologic evaluation, advanced MRI techniques allow the investigation of cerebellar microstructural and functional characteristics. Volumetry, voxel-based morphometry, diffusion MRI based fiber tractography, resting state and task related functional MRI, perfusion, and proton MR spectroscopy are among the most common techniques applied to the study of cerebellum. In the present review, after providing a brief description of each technique's advantages and limitations, we focus on their application to the study of cerebellar injury in major neurodegenerative diseases, such as multiple sclerosis, Parkinson's and Alzheimer's disease and hereditary ataxia. A brief introduction to the pathological substrate of cerebellar involvement is provided for each disease, followed by the review of MRI studies exploring structural and functional cerebellar abnormalities and by a discussion of the clinical relevance of MRI measures of cerebellar damage in terms of both clinical status and cognitive performance
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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