1,720,976 research outputs found
The functional organization of human extrastriate cortex: a PET-rCBF study of selective attention to faces and locations
No full textThe functional dissociation of human extrastriate cortical processing streams for the perception of face identity and location was investigated in healthy men by measuring visual task-related changes in regional cerebral blood flow (rCBF) with positron emission tomography (PET) and H2(15)O. Separate scans were obtained while subjects performed face matching, location matching, or sensorimotor control tasks. The matching tasks used identical stimuli for some scans and stimuli of equivalent visual complexity for others. Face matching was associated with selective rCBF increases in the fusiform gyrus in occipital and occipitotemporal cortex bilaterally and in a right prefrontal area in the inferior frontal gyrus. Location matching was associated with selective rCBF increases in dorsal occipital, superior parietal, and intraparietal sulcus cortex bilaterally and in dorsal right premotor cortex. Decreases in rCBF, relative to the sensorimotor control task, were observed for both matching..
Attention-related modulation of activity in primary and secondary auditory cortex
No full textWe investigated the effects of auditory attention on brain activity using functional magnetic resonance imaging. Subjects listened to three word lists, three times each, and were instructed to count the number of times they heard a target word during two of these presentations. For the third, they listened to the words without counting. All subjects showed significant areas of activation in auditory cortex during the listening conditions compared to rest. There was significantly more activation and a larger area of activation, particularly in association cortex, in the left temporal lobe during counting of targets compared to the no-target conditions, with a similar trend in the right hemisphere. These results provide evidence of an attention-related enhancement of both activation magnitude and extent in auditory cortex
AGE-RELATED REDUCTIONS IN HUMAN RECOGNITION MEMORY DUE TO IMPAIRED ENCODING
No full textThe participation of the medial temporal cortex and other cerebral structures in the memory impairment that accompanies aging was examined by means of positron emission tomography. Cerebral blood flow (rCBF) was measured during encoding and recognition of faces. Young people showed increased rCBF in the right hippocampus and the left prefrontal and temporal cortices during encoding and in the right prefrontal and parietal cortex during recognition. Old people showed no significant activation in areas activated during encoding in young people but did show right prefrontal activation during recognition. Age-related impairments of memory may be due to a failure to encode the stimuli adequately, which is reflected in the lack of cortical and hippocampal activation during encoding
AGE-RELATED CHANGES IN CORTICAL BLOOD FLOW ACTIVATION DURING VISUAL PROCESSING OF FACES AND LOCATION
No full textWe examined age-related changes in object and spatial visual processing in two separate experiments. Regional cerebral blood flow (rCBF) was measured in young and old subjects with positron emission tomography and H2(15)O during tests of face matching, location matching, and a control task. The task demands in the two experiments were identical, but the stimuli in Experiment II were constructed to equalize stimulus complexity across all three tasks. The old subjects performed more slowly than the young subjects in both experiments, and showed significantly slower reaction times during location matching compared to face matching in Experiment II. Both young and old subjects showed occipitotemporal rCBF activation during face matching and occipitoparietal activation during location matching when these conditions were compared to the control task. However, in both experiments and in both tasks, young subjects showed greater activation of prestriate cortex (Brodmann's area 18), and old ..
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
- …
