1,721,039 research outputs found
“Sculpting the response space” – an account of left prefrontal activation at encoding
Full text linkLeft lateral prefrontal cortex (PFC) is consistently activated in neuroimaging studies of memory encoding. Its role, however, remains unclear. We describe two functional magnetic resonance imaging (fMRI) studies addressing this question. In the first we used a blocked experimental design to explore the effect of repeated encoding of word paired associates. Initial presentation of word pairs was associated with left ventrolateral PFC activation that attenuated with subsequent presentations of the same lists. When well-learned lists were presented with word pairs rearranged, a left PFC activation, greater than that associated with the initial presentation, was observed. In a second experiment, the formation of these associative relationships was explored using an event-related design. Two types of word pairs were presented: closely related (e.g., Ring...Queen) and distantly related (e.g., Net...Ship). The same region of left PFC was differentially sensitive to these two event-types, showing a greater response for distantly related pairs
The origins of forgetting in a case of isolated retrograde amnesia following a haemorrhage: evidence from functional imaging
No full textFollowing a left superior dorsolateral prefrontal haemorrhage, a man in his 40s presented with a dense isolated retrograde amnesia for 19 years preceding the stroke. This period of his life contained many highly stressful situations. Functional neuroimaging using PET was carried out while he attempted to recall events using family snapshots as stimuli. There were three conditions - those where the stimuli related to the amnesic period and in which he had been present at the event (amnesic-present condition), analogous events from outside that period (non-amnesic present condition) and events where he was not present (not-present condition). Activation in the amnesic-present condition differed significantly from the other two conditions in three cortical regions. Activation was greater in part of the precuneus, but less in both the right posterior ventrolateral frontal cortex and in a region close to the lesion. We argue that an explanation in terms of malingering can be rejected and instead propose that this deficit can be explained by the fact that the recursive self-cueing of memory traces characteristic of autobiographical retrieval was not properly triggered
The functional imaging of recall
No full textAn associative theory of implicit and explicit memory, G.H. Bower; encoding and retrieval processes - similarities and differences, F.I.M. Craik, M. Naveh-Benjamin, N.D. Anderson; memory imagery - a visual trace is not a mental image, C. Cornoldi, R. de Beni, F. Giusberti, M. Massironi; imaginary memories, E.F. Loftus; the rise and fall of semantic memory, J.M. Mandler; stories, selves and schemata - a review of ecological findings, U. Neisser; associative processes in false recall and false recognition, H.L. Roediger III, K.B. McDermott, K.J. Robinson; the functional imaging of recall, T. Shallice, P. Fletcher, R. Dolan; three dimensions of spatial cognition, B. Tversky. Part contents.
Brain activity during memory retrieval: The influence of imagery and semantic cueing
Full text linkThe effects of imagery and semantic relatedness on cued retrieval of word pairs were examined in a functional imaging study of healthy volunteers. Subjects underwent 12 PET scans, preceded by the paced presentation of 12 paired associates. The associates were dichotomized into imageable and non-imageable groups. Within each group, the strength of semantic association between members of pairs was varied in an ordinal fashion. Subsequently, neural activity was measured while subjects were cued with the first item of each pair and required to recall the associated word. Recall of imageable words, when compared with non-imageable ones, was associated with activation of the precuneus, consistent with our hypothesis that this region is important in visual imagery at episodic retrieval. The reverse comparison, non-imageable versus imageable recall, was associated with activation of the left dorsolateral prefrontal cortex. Within both imageable and non-imageable groups, decreasing semantic association showed a corresponding increase in frontal activity bilaterally. One possible explanation is that of a practice-related effect, weaker-linked pairs having a greater number of pre-scan presentations. However this explanation is incomplete as the most semantically distant, and most rehearsed, pairs (randomly linked) were associated with a reversal of this effect. This finding can be explained if frontal activity is associated with the difficulty of eliminating inappropriate responses at retrieval. For both randomly linked pairs and closely related pairs it is more likely that erroneous responses will be generated and, therefore, the work done to eliminate them will be greater Our findings indicate that patterns of neural activity during cued recall depend upon the nature of the material and on the degree of association between the cue and the response
Is multivariate analysis of PET data more revealing than the univariate approach? Evidence from a study of episodic memory retrieval
Full text linkIn a functional imaging study of cued paired associate retrieval, in which the strength of association between pair members was systematically varied, we predicted increased right frontal activity as a function of weakening semantic linkage. An initial univariate analysis found the opposite effect, with greater right frontal activity during recall of strongly linked paired associates, This unexpected result led us to perform a multivariate analysis of covariance (MANCOVA),an approach which proved more informative, This analysis showed that the most significant source of task-related variance was accounted for by a nonlinear relationship not predicted by the prior hypothesis and not revealed by the standard univariate approach
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
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