1,721,007 research outputs found
Neurale Sturing van het Wandelen: de Rol van het Cerebellum
No full textWalking is a relatively easy task; we can walk without thinking about how to do it. While we are able to walk without thinking about it, from a control perspective, walking is definitely not a simple task. It needs to be stable and efficient in a broad range of different conditions. Insights into the neural control of gait are important to learn us about why specific individuals (patients, elderly) experience difficulties with walking, in general or under specific conditions. With this knowledge rehabilitation and fall prevention strategies can be optimized.While it is known that there is an important role for the spinal circuitry in the neural control of gait, multiple supraspinal structures have been suggested to contribute substantially as well. Specifically, based on common gait deficits in cerebellar patients, the cerebellum can be expected to be important in the neural control of gait. So far this has been evaluated in humans, mainly during unperturbed, steady state walking. An important next step is to study the role of the cerebellum in the control of gait corrections in reaction to perturbations. In those conditions, the cerebellum can be expected to be even more involved in the control of gait, because of its function in comparing expected and real sensory signals.The objective of this thesis was to increase the understanding of the roles of the cerebellum in the control of gait corrections in reaction to perturbations, and of the localization of these functions within the cerebellum. We evaluated the role of the cerebellum in dynamic gait stability, in cutaneous reflex modulation during gait and in locomotor adaptation, all important features of neural control of gait in non-steady state conditions.In the first part, we performed three studies, focusing on the relationship between cutaneous reflex modulation and gait stability, and on the role of the cerebellum in these features. First, we studied cutaneous reflexes during backward walking in healthy controls and observed a prominent phase-dependent reflex modulation during this task. Next, we addressed the potential role of the cerebellum in the control of cutaneous reflexes. Cutaneous reflex modulation was similar between healthy controls and patients with focal cerebellar lesions, but the latter appeared less able to attenuate reflexes to self-induced stimuli. This suggests that the cerebellum is not primarily involved in cutaneous reflex modulation but that it could act in attenuation of self-induced reflex responses. The latter role in locomotion would be consistent with the common view that the cerebellum predicts sensory consequences of movement. Furthermore, biceps femoris muscle activity during the single stance phases was increased in the patient group compared to the controls. This increased activation was likely related to a co-activation strategy to reduce instability of gait. This was supported by findings in our third study, where we evaluated dynamic gait stability in patients with focal cerebellar lesions and in healthy controls. The short-term maximum Lyapunov exponent was higher in cerebellar patients, indicating reduced dynamic gait stability. Furthermore, while step width was increased and self-selected overground walking speed was decreased in the patient group while other spatio-temporal gait parameters were similar. Patients with the largest lesions in the vermis displayed the least stable gait pattern.In the second part, we focused on split-belt walking which, in the past decade, has become a popular paradigm to study the role of the cerebellum in locomotor adaptation. First, we evaluated split-belt adaptation in healthy controls and mildly ataxic patients with focal cerebellar lesions. We observed that during the split-belt adaptation experiment, patients and healthy controls globally displayed similar changes in gait parameters. However, a group difference was observed in the aftereffect of the Stance Time Symmetry: during the early phase of the post-adaptation period the relative stance times were more asymmetric for the patient group than for the control group. Patients who walked with more asymmetric relative stance times were more likely to have lesions in vermal lobules VI and Crus II. In the final study, we assessed the role of somatosensory perception in the control of split-belt walking. We observed that participants who were less able to perceive differences between belt speeds, initially walked with more asymmetric stance times during split-belt walking. This is in line with our general view that load and stretch information are important in the neural control of gait.In conclusion, the cerebellum appears important in the control in dynamic gait stability. Furthermore, our data suggests that the cerebellum is not primarily involved in cutaneous reflex modulation but that it could act in attenuation of self-induced reflex responses. Our results demonstrated that mildly ataxic cerebellar patients show no deficits in split-belt adaptation but exhibit differences in the post-adaptation period. Finally, the observed relations between speed-difference perception and gait asymmetry during split-belt walking confirmed the importance of proprioceptive information in gait control.<w:latentstyles deflockedstate="false" defunhidewhenused="true" <w:lsdexception="" locked="false" priority="0" semihidden="false" status: Publishe
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
Is action-perception coupling improved with delay in patients with focal cerebellar lesions?
No full textstatus: Publishe
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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