1,720,994 research outputs found
The superior parietal lobule of primates: A sensory-motor hub for interaction with the environment
Full text linkThe superior parietal lobule of the macaque monkey occupies the postero-medial part of the parietal lobe and plays a crucial role in the integration of different sources of information (from visual, motor and somatosensory brain regions) for the purpose of high-level cognitive functions, as perception for action. This region encompasses the intraparietal sulcus and the parieto-occipital sulcus and includes also the precuneate cortex in the mesial surface of the hemisphere. It hosts several areas extensively studied in the macaque: PE, PEip, PEci anteriorly and PEc, MIP, PGm and V6A posteriorly. Recently studies based on functional MRI have suggested putative human homologue of some of the areas of the macaque superior parietal lobule. Here we review the anatomical subdivision, the cortico-cortical and thalamocortical connections of the macaque superior parietal lobule compared with their functional properties and the homology with human organization in physiological and lesioned situations. The knowledge of this part of the macaque brain could help in understanding pathological conditions that in humans affect the normal behaviour of arm-reaching actions and can inspire brain computer interfaces performing in more accurate ways the sensorimotor transformations needed to interact with the surrounding environment
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
Role of the p53/p21 system in the response of human colon carcinoma cells to Doxorubicin
No full textBACKGROUND: Colon adenocarcinomas are refractory to a number of widely used anticancer agents. Multifactorial mechanisms have been implicated in this intrinsically resistant phenotype, including deregulation of cell death pathways. In this regard, the p53 protein has a well established role in the control of tumor cell response to DNA damaging agents; however, the relationship between p53-driven genes and drug sensitivity remains controversial. The present study investigates the role of the p53/p21 system in the response of human colon carcinoma cells to treatment with the cytotoxic agent doxorubicin (DOX) and the possibility to modify the therapeutic index of DOX by modulation of p53 and/or p21 protein levels. METHODS: The relationship between p53 and p21 protein levels and the cytotoxic effect of DOX was investigated, by MTT assay and western blot analysis, in HCT116 (p53-positive) and HT29 (p53-negative) colon cancer cells. We then assessed the effects of DOX in two isogenic cell lines derived from HCT116 by abrogating the expression and/or function of p53 and p21 (HCT116-E6 and HCT116 p21-/-, respectively). Finally, we evaluated the effect of pre-treatment with the piperidine nitroxide Tempol (TPL), an agent that was reported to induce p21 expression irrespective of p53 status, on the cytotoxicity of DOX in the four cell lines. Comparisons of IC50 values and apoptotic cell percentages were performed by ANOVA and Bonferroni's test for independent samples. C.I. calculations were performed by the combination Index method. RESULTS: Our results indicate that, in the colon carcinoma cell lines tested, sensitivity to DOX is associated with p21 upregulation upon drug exposure, and DOX cytotoxicity is potentiated by pre-treatment with TPL, but only in those cell lines in which p21 can be upregulated. CONCLUSIONS: p21 induction may significantly contribute to the response of colon adenocarcinomas cells to DOX treatment; and small molecules that can exploit p53-independent pathways for p21 induction, such as TPL, may find a place in chemotherapeutic protocols for the clinical management of colorectal cancer, where p53 function is often lost, due to genetic or epigenetic defects or to post-transcriptional inactivating mechanisms
Vision for action: thalamic and cortical inputs to the macaque superior parietal lobule
Full text linkThe dorsal visual stream, the cortical circuit that in the primate brain is mainly dedicated to the visual control of actions, is split into two routes, a lateral and a medial one, both involved in coding different aspects of sensorimotor control of actions. The lateral route, named “lateral grasping network”, is mainly involved in the control of the distal part of prehension, namely grasping and manipulation. The medial route, named “reach-to-grasp network”, is involved in the control of the full deployment of prehension act, from the direction of arm movement to the shaping of the hand according to the object to be grasped. In macaque monkeys, the reach-to-grasp network (the target of this review) includes areas of the superior parietal lobule (SPL) that hosts visual and somatosensory neurons well suited to control goal-directed limb movements toward stationary as well as moving objects. After a brief summary of the neuronal functional properties of these areas, we will analyze their cortical and thalamic inputs thanks to retrograde neuronal tracers separately injected into the SPL areas V6, V6A, PEc, and PE. These areas receive visual and somatosensory information distributed in a caudorostral, visuosomatic trend, and some of them are directly connected with the dorsal premotor cortex. This review is particularly focused on the origin and type of visual information reaching the SPL, and on the functional role this information can play in guiding limb interaction with objects in structured and dynamic environments
The source scaling and seismic productivity of slow slip transients
Full text linkSlow slip events (SSEs) represent a slow faulting process leading to aseismic strain release often accompanied by seismic tremor or earthquake swarms. The larger SSEs last longer and are often associated with intense and energetic tremor activity, suggesting that aseismic slip controls tremor genesis. A similar pattern has been observed for SSEs that trigger earthquake swarms, although no comparative studies exist on the source parameters of SSEs and tremor or earthquake swarms. We analyze the source scaling of SSEs and associated tremor- or swarm-like seismicity through our newly compiled dataset. We find a correlation between the aseismic and seismic moment release indicating that the shallower SSEs produce larger seismic moment release than deeper SSEs. The scaling may arise from the heterogeneous frictional and rheological properties of faults prone to SSEs and is mainly controlled by temperature. Our results indicate that similar physical phenomena govern tremor and earthquake swarms during SSEs
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
Structural connectivity and functional properties of the macaque superior parietal lobule
Full text linkDespite the consolidated belief that the macaque superior parietal lobule (SPL) is entirely occupied by Brodmann’s area 5, recent data show that macaque SPL also hosts a large cortical region with structural and functional features similar to that of Brodmann’s area 7. According to these data, the anterior part of SPL is occupied by a somatosensory-dominated cortical region that hosts three architectural and functional distinct regions (PE, PEci, PEip) and the caudal half of SPL by a bimodal somato-visual region that hosts four areas: PEc, MIP, PGm, V6A. To date, the most studied areas of SPL are PE, PEc, and V6A. PE is essentially a high-order somatomotor area, while PEc and V6A are bimodal somatomotor–visuomotor areas, the former with predominant somatosensory input and the latter with predominant visual input. The functional properties of these areas and their anatomical connectivity strongly suggest their involvement in the control of limb movements. PE is suggested to be involved in the preparation/execution of limb movements, in particular, the movements of the upper limb; PEc in the control of movements of both upper and lower limbs, as well as in their interaction with the visual environment; V6A in the control of reach-to-grasp movements performed with the upper limb. In humans, SPL is traditionally considered to have a different organization with respect to macaques. Here, we review several lines of evidence suggesting that this is not the case, showing a similar structure for human and non-human primate SPLs
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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