3,697 research outputs found
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.
“Sculpting the response space” – an account of left prefrontal activation at encoding
No full textLeft 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 promises and pitfalls of sex integration in sport and physical culture
No full textScholars working in the academic field of sport studies have long debated the relationship between modern sport and gender (e.g. Hargreaves and Anderson, 2014; Hargreaves, 1994; Lenskyj, 1986; Messner, 2002). Within this body of work, modern sport forms – along with a great diversity of related activities, including dance, fitness training, physical education, etc. – have consistently been shown to carry meanings relative to the structures of gender prevailing in the wider social settings within which they take place, with patterns of participation and consumption clearly mapping onto gendered ideals. However, rather than simply mirroring such social norms, research suggests that many sporting practices were invented or have been purposefully developed in order to train young men and women in socially-approved gender behaviors to begin with (Cahn 1994; Hargreaves 1994; Theberge, 2000). Thus, much of contemporary physical culture finds its roots in the process which scholars describe as the ‘social construction of gender’; in other words, doing sports and other activities in gender-differentiated ways has long been a means of producing and maintaining difference in the lives of men and women, girls and boys.Peer reviewedAccepted author manuscript of a peer reviewed article accepted for publication by Taylor & Francis in Sport in Society: Cultures, Commerce, Media, Politics online on 28/12/2015
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
Brain activity during memory retrieval: The influence of imagery and semantic cueing
No full textThe 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
No full textIn 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
Preclinical evaluation of lime juice as a topical microbicide candidate
No full textBackground: The continued growth of the global HIV epidemic highlights the urgent need to develop novel prevention strategies to reduce HIV transmission. The development of topical microbicides is likely to take a number of years before such a product would be widely available.
This has resulted in a call for the rapid introduction of simpler vaginal intervention strategies in the interim period. One suggested practice would be vaginal douching with natural products including lime or lemon juice. Here we present a comprehensive preclinical evaluation of lime juice (LiJ) as a potential intervention strategy against HIV.
Results: Pre-treatment of HIV with LiJ demonstrated direct virucidal activity, with 10% juice inactivating the virus within 5 minutes. However, this activity was significantly reduced in the presence of seminal plasma, where inactivation required maintaining a 1:1 mixture of neat LiJ and seminal plasma for more than 5 minutes. Additionally, LiJ demonstrated both time and dosedependent
toxicity towards cervicovaginal epithelium, where exposure to 50% juice caused 75–90% toxicity within 5 minutes increasing to 95% by 30 minutes. Cervicovaginal epithelial cell monolayers were more susceptible to the effects of LiJ with 8.8% juice causing 50% toxicity after 5
minutes. Reconstructed stratified cervicovaginal epithelium appeared more resilient to LiJ toxicity with 30 minutes exposure to 50% LiJ having little effect on viability. However viability was reduced by 75% and 90% following 60 and 120 minutes exposure. Furthermore, repeat application (several times daily) of 25% LiJ caused 80–90% reduction in viability.
Conclusion: These data demonstrate that the virucidal activity of LiJ is severely compromised in the presence of seminal plasma. Potentially, to be effective against HIV in vivo, women would need to apply a volume of neat LiJ equal to that of an ejaculate, and maintain this ratio vaginally for 5–30 minutes after ejaculation. Data presented here suggest that this would have significant adverse
effects on the genital mucosa. These data raise serious questions about the plausibility and safety of such a prevention approach
Brain systems for encoding and retrieval of auditory - Verbal memory. An in vivo study in humans
No full textLong-term auditory-verbal memory comprises, at a neuropsycho logical level, a number of distinct cognitive processes. In the present study we determined the brain systems engaged during encoding (experiment I) and retrieval (experiment 2) of episodic auditory-verbal material. In the separate experiments, PET measurements of regional cerebral blood flow (rCBF), an index of neural activity, were performed in normal volunteers during either the encoding or the retrieval of paired word associates. In experiment I, a dual task interference paradigm was used to isolate areas involved in episodic encoding from those which would be concurrently activated by other cognitive processes associated with the presentation of paired associates, notably priming. In experiment 2, we used the cued retrieval of paired associates from episodic or from semantic memory in order to isolate the neural correlates of episodic memories. Encoding of episodic memory was associated with activation of the left prefrontal cortex and the retrosplenial area of the cingulate cortex, while retrieval from episodic memory was associated with activation of the precuneus bilaterally and of the right prefrontal cortex. These results are compatible with the patterns of activation reported in a previous PET memory experiment in which encoding and retrieval were studied concurrently. They also indicate that separate brain systems are engaged during the encoding and retrieval phases of episodic auditory-verbal memory. Retrieval from episodic memory engages a different, but overlapping, system to that engaged by retrieval from semantic memory, a finding that lends functional anatomical support to this neuro-psychological distinction. © 1995 Oxford University Press
The mind’s eye—recuneus activation in memory-related imagery
No full textWe examined brain activity associated with visual imagery at episodic memory retrieval using positron emission tomography (PET). Twelve measurements of regional cerebral blood flow (rCBF) were taken in six right- handed, healthy, male volunteers. During six measurements, they were engaged in the cued recall of imageable verbal paired associates. During the other six measurements, they recalled nonimageable paired associates. Memory performance was equalized across all word lists. The subjects’ use of an increased degree of visual imagery during the recall of imageable paired associates was confirmed using subjective rating scales after each scan. Memory-related imagery was associated with significant activation of a medial parietal area, the precuneus. This finding confirms a previously stated hypothesis about the precuneus and provides strong evidence that it is a key part of the neural substate of visual imagery occurring in conscious memory recall. © 1995 by Academic press, Inc
Reformulating the rj-McMC Algorithm for 3D Inversion of Passive Seismic Data for Near-Surface Characterization
No full textGeophysical subsurface characterization techniques could, due to their non-invasive nature, play a crucial role in the design and subsequent construction of infrastructure in urban & industrial environ- ments. Geo-data specialist company Fugro sees potential in upgrading their current ambient-seismic- noise-tomography workflow, to make use of state-of-the-art inversion schemes with the main goal of increasing the quality and accuracy of the initial-site characterization delivered to clients. In this thesis I explore the feasibility of utilizing the reverse-jump Markov chain Monte Carlo (rj-McMC) algorithm for the inversion of ambient seismic noise for characterization in urban & industrial environments. Specif- ically, testing the potential of scaling down this inversion algorithm to fit in a small scale, near-surface framework. To achieve this, I first carried out analyses to evaluate the appropriate Rayleigh wave frequency range, after which realistic noise hyperparameters, suited for this reduced scale problem, were obtained. Because of the potential exploitation of in-situ borehole measurements, I reformulated the Bayesian prior within the rj-McMC algorithm to implement these constraining shear wave velocity values appropriately. I conducted extensive synthetic experiments to gain insight into the behavior of this adapted algorithm, from which it was concluded that the inherent dynamic discretization partially prevents these constraints from being implemented to their full extent. Nevertheless, promising results lead me to conclude that the use of the rj-McMC algorithm for application in near-surface urban & industrial environments is feasible.Applied Geophysics | IDEA Leagu
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