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Il controllo corticale inibitorio nella Malattia di Parkinson: ruolo della stimolazione transcranica a corrente alternata nella modulazione di oscillazioni beta/gamma a livello delle aree corticali frontali
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Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Abnormal cortical facilitation and L-dopa-induced dyskinesia in Parkinson's disease
No full textBackground
Animal models of Parkinson's Disease (PD) demonstrated increased facilitatory cortico-striatal activity, reflecting overactive glutamatergic neurotransmission and contributing to the pathophysiology of l-dopa induced dyskinesias (LIDs).
Objective
To assess different facilitatory intracortical circuits in the primary motor cortex (M1) in patients with PD and LIDs by means of a combination of transcranial magnetic stimulation (TMS) protocols.
Methods
We tested the Input/Output (I/O) curve, intracortical facilitation (ICF) and short-interval intracortical facilitation (SICF) at baseline (T0), ‘OFF’ and ‘ON’ state, in 20 PD patients with LIDs. The same parameters were examined after 2 weeks of chronic intake of 50 mg (T1) and 100 mg/day (T2) of safinamide. Finally, we tested SICF in a further group of patients without LIDs.
Results
At T0, patients with LIDs showed increased I/O curve steepness, which was partly ameliorated by l-dopa. These patients also had normal ICF, and abnormally increased SICF, which did not change with l-dopa. Safinamide improved the I/O curve both at T1 and T2, it reduced SICF at T1 and normalized this measure at T2. In patients with PD and LIDs, SICF correlated with the severity of dyskinesia. In patients without LIDs, SICF was less prominently abnormal and responsive to l-dopa.
Conclusions
Patients with PD and LIDs have abnormal cortical facilitation, possibly suggesting overactive glutamatergic neurotransmission in specific circuits within M1. Although not responsive to l-dopa, this dysfunction is restored by the anti-glutamatergic properties of safinamide 100 mg. The results suggest that the abnormal cortical facilitation in M1 contributes to the pathophysiology of LIDs
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
Fractal Dimension as a discriminative feature for high accuracy classification in motor imagery EEG-based brain-computer interface
No full textBackground and objective: The brain-computer interface (BCI) technology acquires human brain electrical signals, which can be effectively and successfully used to control external devices, potentially supporting subjects suffering from motor impairments in the interaction with the environment. To this aim, BCI systems must correctly decode and interpret neurophysiological signals reflecting the intention of the subjects to move. Therefore, the accurate classification of single events in motor tasks represents a fundamental challenge in ensuring efficient communication and control between users and BCIs. Movement-associated changes in electroencephalographic (EEG) sensorimotor rhythms, such as event-related desynchronization (ERD), are well-known features of discriminating motor tasks. Fractal dimension (FD) can be used to evaluate the complexity and self-similarity in brain signals, potentially providing complementary information to frequency-based signal features. Methods: In the present work, we introduce FD as a novel feature for subject-independent event classification, and we test several machine learning (ML) models in behavioural tasks of motor imagery (MI) and motor execution (ME). Results: Our results show that FD improves the classification accuracy of ML compared to ERD. Furthermore, unilateral hand movements have higher classification accuracy than bilateral movements in both MI and ME tasks. Conclusions: These results provide further insights into subject-independent event classification in BCI systems and demonstrate the potential of FD as a discriminative feature for EEG signals
Enhancing gamma oscillations restores primary motor cortex plasticity in Parkinson's disease
Get PDFIn humans, gamma (γ) oscillations in cortical motor areas reflect asynchronous synaptic activity and contribute to plasticity processes. In Parkinson's disease (PD), γ oscillatory activity in the basal ganglia-thalamo-cortical network is altered and the long-term potentiation (LTP)-like plasticity elicited by intermittent theta burst stimulation (iTBS) is reduced in the primary motor cortex (M1). In this study, we tested whether transcranial alternating current stimulation (tACS) delivered at γ frequency promotes iTBS-induced LTP-like plasticity in M1 in PD patients. Sixteen patients ('OFF' condition) and 16 healthy subjects (HS) underwent iTBS during γ-tACS (iTBS-γ tACS) and during sham-tACS (iTBS-sham tACS) in two sessions. Motor-evoked potentials (MEPs) evoked by single-pulse TMS and short-interval intracortical inhibition (SICI) were recorded before and after the co-stimulation. A subgroup of patients also underwent iTBS during β tACS. iTBS-sham tACS facilitated single-pulse MEPs in HS, but not in patients. iTBS-γ tACS induced a larger MEPs facilitation than iTBS-sham tACS in both groups, with similar values in patients and HS. In patients, SICI improved after iTBS-γ tACS. The effect produced by iTBS-γ tACS on single-pulse MEPs correlated with disease duration, while changes in SICI correlated with UPDRS-III scores. The effect of iTBS-β tACS on both single-pulse MEPs and SICI was similar to that obtained in the iTBS-sham tACS session. Our data suggest that γ oscillations have a role in the pathophysiology of the abnormal LTP-like plasticity in PD. Entraining M1 neurons at the γ rhythm through tACS may be an effective method to restore impaired plasticity.SIGNIFICANCE STATEMENTIn Parkinson's disease, the LTP-like plasticity of the primary motor cortex is impaired, and gamma oscillations are altered in the basal ganglia-thalamo-cortical network. Using a combined TMS-tACS approach (iTBS-γ tACS co-stimulation), we demonstrate that driving gamma oscillations restores the LTP-like plasticity in patients with Parkinson's disease. The effects correlate with clinical characteristics of patients, being more evident in less affected patients and weaker in patients with longer disease duration. These findings suggest that cortical gamma oscillations play a beneficial role in modulating the LTP-like plasticity of M1 in Parkinson's disease. The iTBS-γ tACS approach may be potentially useful in rehabilitative settings in patients
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