322,908 research outputs found
Prefrontal and temporo-parietal involvement in taking others' perspective: TMS evidence.
No full textINTRODUCTION:
Understanding the mental states of others entails a number of cognitive processes known as Theory of Mind (ToM). Behavioural and functional neuroimaging evidence suggests that prefrontal and temporo-parietal cortices are involved in these abilities. The present study was aimed at investigating the role of the dorsolateral prefrontal cortex and temporo-parietal junction in ToM by using a repetitive transcranial magnetic stimulation (rTMS) paradigm.
MATERIAL AND METHODS:
Eleven healthy subjects participated in the study. The experimental ToM procedure was constituted by false belief and faux-pas written stories. Subjects were evaluated in baseline condition (Sham) and after 1Hz rTMS over the left/right dorsolateral prefrontal cortex and temporo-parietal junction. A score for accuracy and response times were recorded.
RESULTS:
As regards false beliefs, rTMS over right prefrontal and temporo-parietal areas significantly interfered with response times (p<0.05$). The application of rTMS over right/left prefrontal and right temporo-parietal cortices also significantly worsened accuracy in the ability to take the others' perspective in faux-pas tasks as compared to Sham (p <or= 0.05 in all cases).
CONCLUSIONS:
The results of the present study are consistent with previous findings supporting the hypothesis that prefrontal and temporo-parietal regions are part of a neural network specifically underpinning the ability to attribute mental states to others
Modulation of excitatory and inhibitory circuits for visual awareness in the human right parietal cortex
No full textThe balance of specific patterns of excitation and inhibition in critical regions of both hemispheres could be relevant in orienting attention over the extrapersonal space. In the present study a group of normal subjects had to detect small rectangular stimuli presented briefly on a computer screen in three different conditions: unilateral presentation either to left or right visual periphery or bilateral simultaneous presentation. Paired transcranial magnetic stimulation (TMS), was applied over the right parietal cortex 150 ms after the presentation of the visual stimuli with different inter-stimulus intervals (ISIs: 1, 3,5 and 10 ms). When paired TMS was applied 150 ms, but not 100 ms, after simultaneous visual presentation, the number of failures in detecting left targets increased compared to the single-pulse condition if the ISI was 3 ms; on the contrary, it decreased if the ISI was 5 ms. No effects were seen when paired pulses of the same intensity were delivered. These findings provide evidence of a supramodal-specific pattern of excitability of the right posterior parietal cortex in processing visuospatial information
Sicut nunc cernitur satis pulcherrimam construxit. La chiesa e gli affreschi desideriani di S. Benedetto a Capua
No full textlo studio identifica un edificio medievale che si credeva distrutto, ricomponendone l'assetto originale a partire dagli elementi che ne sono stati recuperati dopo il restauro
Extending assortativity: An application to weighted social networks
No full textAssortativity by degree for complex networks is quantified by the Newman coefficient, and it describes a tendency for nodes to be connected to others with a similar degree. A generalization of the assortativity index has been proposed in the literature for undirected and unweighted networks, analysing the correlation between vertices that are not necessarily adjacent, but connected through paths, shortest paths and random walks. The aim of this study is to define a new class of higher-order assortativity measures for weighted networks. The effectiveness of these measures is evident in social networks, where both weights and connections are significant. Applications to Facebook and co-authorship networks are provided, analysing the assortativity beyond the nearest neighbours
Betweenness Centrality: Extremal Values and Structural Properties
No full textIn this paper we investigate the structural properties of betweenness centrality and determine some cases in which betweenness reaches its extremal values. Special attention is paid to Star(G), the set of vertices adjacent to all other vertices in a graph and we prove several results about the betweenness of the elements of this set. We introduce the new concept of total betweenness and relate it to group betweenness. We prove a
necessary and sufficient condition for the two measures to coincide. Next we consider cutsets and cutvertices and we find a lower bound for their betweenness; in particular for a cutvertex this lower bound is the cutting number. Finally we apply the previous results to trees, proving an alternative formula for betweenness based on cutvertex properties
Increased facilitation of the primary motor cortex following 1Hz repetitive transcranial magnetic stimulation of the contralateral cerebellum in normal humans
No full textConnections between the cerebellum and the contralateral motor cortex are dense and important, but their physiological significance is difficult to measure in humans. We have studied a group of 10 healthy subjects to test whether a modulation of the excitability of the left cerebellum can affect the excitability of the contralateral motor cortex. We used repetitive transcranial magnetic stimulation (rTMS) at 1 Hz frequency to transiently depress the excitability of the left cerebellar cortex and paired-pulse TMS testing of intracortical inhibition (ICI) and intracortical facilitation (ICF) to probe the excitability of cortico-cortical connections in the right motor cortex. The cortical silent period was also measured before and after cerebellar rTMS. Motor evoked potentials (MEPs) were significantly larger after than before conditioning rTMS trains (p < 0.01). Moreover, left cerebellar rTMS increased the ICF of the right motor cortex as measured with paired-pulses separated by an interstimulus interval (ISI) of 15 ms. The effect lasted for up to 30 min afterward and was specific for the contralateral (right) motor cortex. The cortical silent period was unaffected by cerebellar rTMS. The implication is that rTMS of the cerebellar cortex can shape the flowing of inhibition from Purkinje cells toward deep nuclei, thereby increasing the excitability of interconnected brain areas
Underestimation of time perception after repetitive transcranial magnetic stimulation
No full textThe right dorsolateral prefrontal cortex (rDLPFC) may be important in time perception in humans. In the
present study, the authors demonstrate that a virtual lesion of the rDLPFC by repetitive transcranial magnetic stimulation (rTMS) leads to underestimation of time perception for brief intervals (lasting a few seconds) in working memory
Extremal properties of graphs and eigencentrality in trees with a given degree sequence
No full textIn this article, we investigate several issues related to the use of the index
S(G), known as the Zagreb index (see Gutman and Das, 2004) or “S-metric”
(Alderson and Li, 2007). We present some new upper and lower bounds
for S(G), in terms of the degree sequence of G. Then, we concentrate on trees and prove that in trees with maximum S(G) the eigenvector ordering is coherent with the degree ordering; that is, degree central vertices are also eigenvector central. This confirms results given in Bonacich (2007). Further, we show that these trees
have minimum diameter and maximum spectral radius in the set of trees with a given degree sequence. A simple application to a company organizational network is provided
Interference of left and right cerebellar rTMS with procedural learning
No full textIncreasing evidence suggests cerebellar involvement in procedural learning. To further analyze its role and to assess whether it has a lateralized influence, in the present study we used a repetitive transcranial magnetic stimulation interference approach in a group of normal subjects performing a serial reaction time task. We studied 36 normal volunteers: 13 subjects underwent repetitive transcranial magnetic stimulation on the left cerebellum and performed the task with the right (6 subjects) or left (7 subjects) hand; 10 subjects underwent repetitive transcranial magnetic stimulation on the right cerebellum and performed the task with the hand ipsilateral (5 subjects) or contralateral (5 subjects) to the stimulation; another 13 subjects served as controls and were not submitted to repetitive transcranial magnetic stimulation; 7 of them performed the task with the right hand and 6 with the left hand. The main results show that interference with the activity of the lateral cerebellum induces a significant decrease of procedural learning: Interference with the right cerebellar hemisphere activity induces a significant decrease in procedural learning regardless of the hand used to perform the serial reaction time task, whereas left cerebellar hemisphere activity seems more linked with procedural learning through the ipsilateral hand. In conclusion, the present study shows for the first time that a transient interference with the functions of the cerebellar cortex results in an impairment of procedural learning in normal subjects and it provides new evidences for interhemispheric differences in the lateral cerebellum
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