1,720,964 research outputs found
Phonological short-term store impairment after cerebellar lesion: A single case study
No full textThe cerebellum is a recent addition to the growing list of cerebral areas involved in the multifaceted structural system that sustains verbal working memory (vWM), but its contribution is still a matter of debate. Here, we present a patient with a selective deficit of vWM resulting from a bilateral cerebellar ischemic lesion. After this acute event, the patient had impaired immediate and delayed word-serial recall and auditory-verbal delayed recognition. The digit span, however, was completely preserved. To investigate the cerebellar contribution to vWM, four experiments addressing the function of different vWM phonological loop components were performed 18 months after the lesion, and results were compared with normative data or, when needed, with a small group of matched controls. In Experiment 1, digit span was assessed with different presentation and response modalities using lists of digits of varying lengths. In Experiment 2, the articulatory rehearsal system was analyzed by measurement of word length and articulatory suppression effects. Experiment 3 was devoted to analyzing the phonological short-term store (ph-STS) by the recency effect, the phonological similarity effect, short-term forgetting, and unattended speech. Data suggested a possible key role of the semantic component of the processed material, which was tested in Experiment 4, in which word and nonword-serial recall with or without interpolating activity were analyzed. The patient showed noticeably reduced scores in the tasks that primarily or exclusively engaged activity of the ph-STS, namely those of Experiment 3, and good performance in the tests that investigated the recirculation of verbal information. This pattern of results implicates the ph-STS as the cognitive locus of the patient's deficit. This report demonstrates a cerebellar role in encoding and/or strengthening the phonological traces in vWM. (c) 2008 Elsevier Ltd. All rights reserved.The cerebellum is a recent addition to the growing list of cerebral areas involved in the multifaceted structural system that sustains verbal working memory (vWM), but its contribution is still a matter of debate. Here, we present a patient with a selective deficit of vWM resulting from a bilateral cerebellar ischemic lesion. After this acute event, the patient had impaired immediate and delayed word-serial recall and auditory-verbal delayed recognition. The digit span, however, was completely preserved. To investigate the cerebellar contribution to vWM, four experiments addressing the function of different vWM phonological loop components were performed 18 months after the lesion, and results were compared with normative data or, when needed, with a small group of matched controls. In Experiment 1, digit span was assessed with different presentation and response modalities using lists of digits of varying lengths. In Experiment 2, the articulatory rehearsal system was analyzed by mea
Cerebellum and Detection of Sequences, from Perception to Cognition
No full textThe idea that cerebellar processing is required in a variety of cognitive functions is well accepted in the neuroscience community. Nevertheless, the definition of its role in the different cognitive domains remains rather elusive. Current data on perceptual and cognitive processing are reviewed with special emphasis on cerebellar sequencing properties. Evidences, obtained by neurophysiological and neuropsychological lesion studies, converge in highlighting comparison of temporal and spatial information for sequence detection as the key stone of cerebellar functioning across modalities. The hypothesis that sequence detection might represent the main contribution of cerebellar physiology to brain functioning is presented and the possible clinical significance in cerebellar-related diseases discussed.The idea that cerebellar processing is required in a variety of cognitive functions is well accepted in the neuroscience community. Nevertheless, the definition of its role in the different cognitive domains remains rather elusive. Current data on perceptual and cognitive processing are reviewed with special emphasis on cerebellar sequencing properties. Evidences, obtained by neurophysiological and neuropsychological lesion studies, converge in highlighting comparison of temporal and spatial information for sequence detection as the key stone of cerebellar functioning across modalities. The hypothesis that sequence detection might represent the main contribution of cerebellar physiology to brain functioning is presented and the possible clinical significance in cerebellar-related diseases discussed
Oculomotor deficits affect neuropsychological performance in oculomotor apraxia type 2
No full textIntroduction: Ataxia with oculomotor aprmda type 2 is a rare and early-disabling neurode-generative disease, part of a subgroup of autosomal recessive cerebellar ataxia, in which oculomotor symptoms (e.g., increased saccade latency and hypometria) and executive function deficits have been described. The aim of this study was to evaluate the impact of oculomotor symptoms on cognitive performance and, in particular, over reading in 2 Italian siblings affected by ataxia with oculomotor apraxia type 2. Methods: The neuropsychological profiles and the oculomotor patterns during nonverbal and verbal tasks were recorded and analyzed. Results: Saccadic intrusions and/or nystagmus were observed in all eye movement tasks. The neuropsychological profiles were substantially preserved, with only subtle deficits that affected visuomotor integration and attention. Reading ability decreased and became impaired. The reading scan was disturbed by saccadic intrusions and/or nystagmus. However, an ad hoc reading task demonstrated that deficits appeared only when the items that were displayed enhanced oculomotor requests. The preservation of lexical-semantic processes confirmed that the reading disability was caused by oculomotor deficits, not cognitive problems. Conclusion: Present findings indicate that in patients who are affected by ataxia with oculomotor apraxia type 2, performance on neuropsychological tests, especially those that require rapid performance and eye or hand eye control, must be analyzed with respect to oculomotor components. (C) 2012 Elsevier Ltd. All rights reserved.Introduction: Ataxia with oculomotor apraxia type 2 is a rare and early-disabling neurodegenerative disease, part of a subgroup of autosomal recessive cerebellar ataxia, in which oculomotor symptoms (e.g., increased saccade latency and hypometria) and executive function deficits have been described. The aim of this study was to evaluate the impact of oculomotor symptoms on cognitive performance and, in particular, over reading in 2 Italian siblings affected by ataxia with oculomotor apraxia type 2. Methods: The neuropsychological profiles and the oculomotor patterns during nonverbal and verbal tasks were recorded and analyzed. Results: Saccadic intrusions and/or nystagmus were observed in all eye movement tasks. The neuropsychological profiles were substantially preserved, with only subtle deficits that affected visuomotor integration and attention. Reading ability decreased and became impaired. The reading scan was disturbed by saccadic intrusions and/or nystagmus. However, an ad ho
Cerebellar Damage Impairs Executive Control and Monitoring of Movement Generation
No full textExecutive control of motor responses is a psychological construct of the executive system. Several studies have demonstrated the involvement of the cerebral cortex, basal ganglia, and thalamus in the inhibition of actions and monitoring of performance. The involvement of the cerebellum in cognitive function and its functional interaction with basal ganglia have recently been reported. Based on these findings, we examined the hypothesis of cerebellar involvement in executive control by administering a countermanding task in patients with focal cerebellar damage. The countermanding task requires one to make a movement in response to a 'go' signal and to halt it when a 'stop' signal is presented. The duration of the go process (reaction time; RT), the duration of the stop process (stop signal reaction time; SSRT), and their relationship, expressed by a psychometric function, are recorded as measures of executive control. All patients had longer go process duration in general and in particular, as a proactive control, as demonstrated by the increase in RT after erroneously performed stop trials. Further, they were defective in the slope of the psychometric function indicating a difficulty on triggering the stop process, although the SSRT did not differ from controls. Notably, their performance was worse when lesions affected deep cerebellar nuclei. Our results support the hypothesis that the cerebellum regulates the executive control of voluntary actions. We speculate that its activity is attributed to specific cerebellar influence over the cortico-striatal loop
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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