Tesi sul tema "Memory processes"
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1
Whitt, Emma. "Associative processes in recognition memory". Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/12289/.
Testo completoAbstract (sommario):
Recognition memory, or the discrimination between novelty and familiarity, is well predicted by an associative model of memory (Wagner’s SOP). In this thesis I examined predictions from this model concerning priming of stimuli, and stimulus spacing, in rats’ object recognition. Priming of an object resulted in a bias in behaviour towards the non-primed object. This may be due to associative processes, as described by the SOP model. Spacing stimuli in a sample stage of an object recognition task resulted in longer-lasting or better discrimination in a test of familiar versus novel object, as predicted by the model. Incorporating a short or long delay between sample and test led to better discrimination after a short delay, though differences in stimulus spacing conditions at each delay were not significant. I also examined recognition using stimulus generalisation. Generalisation of a conditioned response occurred between stimuli that shared elements of familiarity. Although not significant, familiarity generalisation may have been less apparent in animals with lesions to perirhinal cortex, providing some support for the suggestion that perirhinal cortex has a role in novelty/familiarity discrimination. The main conclusion was that recognition memory, as measured by the object recognition and generalisation tasks, might involve associative processes.
2
Hassabis, D. "Neural processes underpinning episodic memory". Thesis, University College London (University of London), 2009. http://discovery.ucl.ac.uk/16126/.
Testo completoAbstract (sommario):
Episodic memory is the memory for our personal past experiences. Although numerous functional magnetic resonance imaging (fMRI) studies investigating its neural basis have revealed a consistent and distributed network of associated brain regions, surprisingly little is known about the contributions individual brain areas make to the recollective experience. In this thesis I address this fundamental issue by employing a range of different experimental techniques including neuropsychological testing, virtual reality environments, whole brain and high spatial resolution fMRI, and multivariate pattern analysis. Episodic memory recall is widely agreed to be a reconstructive process, one that is known to be critically reliant on the hippocampus. I therefore hypothesised that the same neural machinery responsible for reconstruction might also support ‘constructive’ cognitive functions such as imagination. To test this proposal, patients with focal damage to the hippocampus bilaterally were asked to imagine new experiences and were found to be impaired relative to matched control participants. Moreover, driving this deficit was a lack of spatial coherence in their imagined experiences, pointing to a role for the hippocampus in binding together the disparate elements of a scene. A subsequent fMRI study involving healthy participants compared the recall of real memories with the construction of imaginary memories. This revealed a fronto-temporo-parietal network in common to both tasks that included the hippocampus, ventromedial prefrontal, retrosplenial and parietal cortices. Based on these results I advanced the notion that this network might support the process of ‘scene construction’, defined as the generation and maintenance of a complex and coherent spatial context. Furthermore, I argued that this scene construction network might underpin other important cognitive functions besides episodic memory and imagination, such as navigation and thinking about the future. It is has been proposed that spatial context may act as the scaffold around which episodic memories are built. Given the hippocampus appears to play a critical role in imagination by supporting the creation of a rich coherent spatial scene, I sought to explore the nature of this hippocampal spatial code in a novel way. By combining high spatial resolution fMRI with multivariate pattern analysis techniques it proved possible to accurately determine where a subject was located in a virtual reality environment based solely on the pattern of activity across hippocampal voxels. For this to have been possible, the hippocampal population code must be large and non-uniform. I then extended these techniques to the domain of episodic memory by showing that individual memories could be accurately decoded from the pattern of activity across hippocampal voxels, thus identifying individual memory traces. I consider these findings together with other recent advances in the episodic memory field, and present a new perspective on the role of the hippocampus in episodic recollection. I discuss how this new (and preliminary) framework compares with current prevailing theories of hippocampal function, and suggest how it might account for some previously contradictory data.
3
Colden, Albina. "Empathic processes in human memory". Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615024.
Testo completo
4
Neto, Fernando Fernandes. "Essays on long memory processes". Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/3/3139/tde-03032017-104452/.
Testo completoAbstract (sommario):
The present work aims at discussing the main theoretical aspects related to the occurrence of long memory processes and its respective application in economics and finance. In order to discuss the main theoretical aspects of its occurrence, it is worth starting from the complex systems approach and emergent phenomena, keeping in mind that many of these are computationally irreducible. In other words, the current state of the system depends on all previous states, in such a way that any change in the initial configuration must cause a significant difference in all posterior states. That is, there is a persistence of information over time - this is a concept directly related to long memory processes. Hence, based on complex systems simulations, three factors (possibly there are many others) were related to the rise of long memory processes: agents\' heterogeneity, occurrence of large deviations from the steady states (in conjunction with the motion laws of each system) and spatial complexity (which must influence on information propagation and on the dynamics of agents competition). In relation to the applied knowledge, first it is recognized that the explanatory factors for the rise of long memory processes are common to the structures/characteristics of real markets and it is possible to identify potential stylized facts when filtering the long memory components from time series - a considerable part of information present in time series is a consequence of the autocorrelation structure, which is directly related to the specificities of each market. Given that, in this thesis was developed a new risk contagion technique that does not need any further intervention. This technique is basically given by the calculation of rolling correlations between long memory filtered series of the conditional variances for different economies, such that these filtered series contain the stylized facts (risk peaks), free from possible overreactions caused by market idiosyncrasies. Then, based on the identification of risk contagion episodes related to the 2007/2008 Subprime Crisis in the U.S. and its respective contagion to the Brazilian economy, it was filtered out from the conditional variance of the Brazilian assets (which are an uncertainty measure) aiming at eliminating the contagion episodes and, consequently, it was made a counterfactual projection of what would have happened to the Brazilian economy if the risk contagion episodes had not occurred. Moreover, in conjunction with the evolutionary trend of the Brazilian economy prior to the crisis, it is possible to conclude that 70% of the economic crisis posterior to the 2008 events was caused by macroeconomic policies and only 30% is due to the effects of risk contagion episodes from the U.S.O presente trabalho tem como objetivo discutir os principais aspectos teóricos ligados à ocorrência dos processos de memória longa e sua respectiva aplicação em economia e finanças. Para discutir os principais aspectos teóricos da sua ocorrência, recorre-se primeiramente à abordagem de sistemas complexos e fenômenos emergentes, tendo em vista que muitos destes são irredutíveis computacionalmente, ou seja, o estado atual do sistema depende de todos os estados anteriores, tal que, qualquer mudança nos instantes iniciais deve causar significativa diferença nos estados posteriores. Em outras palavras, há uma persistência da informação - conceito este intimamente ligado à memória longa. Portanto, com base em simulações de sistemas complexos computacionais, três fatores (podendo haver outros mais) foram relacionados ao surgimento de processos de memória longa: heterogeneidade dos agentes, ocorrência de grandes desvios do equilíbrio do sistema (em consonância com as respectivas leis do movimento de cada sistema estudado) e a complexidade espacial (que deve influenciar na propagação da informação e na dinâmica competitiva dos agentes). Em relação à aplicação do conhecimento, primeiro é reconhecido que os fatores explicativos para o surgimento de processos de memória longa são inerentes a estruturas/características de mercados reais e que é possível identificar potenciais fatos estilizados, ao filtrar as componentes de memória longa de séries temporais - grande parte da informação presente nas séries é função da estrutura de autocorrelação que advém das especificidades de cada mercado. Com base nisso, nesta tese foi desenvolvida uma nova técnica de estimação de contágio de risco, que não necessita intervenções adicionais, tendo em vista a identificação prévia de potenciais fatos estilizados em diferentes economias, utilizando as séries filtradas de variância condicional, tal que a partir destas séries filtradas é calculada uma correlação com horizonte móvel de observações entre choques (picos de risco) de curto prazo livres de possíveis reações causadas por idiossincrasias de cada mercado. Posteriormente, com base na identificação dos episódios ligados à Crise do Subprime de 2007/2008 nos Estados Unidos e seu respectivo contágio para a economia brasileira, filtrou-se a variância condicional dos ativos brasileiros (que é uma medida de incerteza), objetivando-se eliminar os eventos de contágio e, consequentemente, foi feita uma projeção contrafactual da evolução da economia, caso os episódios da crise não tivessem ocorrido. Com base nestes dados e com uma análise da tendência evolutiva da economia brasileira no período anterior à crise, constatou-se que 70% da crise econômica vivenciada no Brasil no período pós-2008 é decorrente de falhas na condução da política macroeconômica e somente 30% decorre dos efeitos do cenário externo na economia.
5
Golinski, Adam. "Asset pricing with long memory processes". Thesis, Imperial College London, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.534973.
Testo completo
6
Kenny, Lucy Margaret Psychology Faculty of Science UNSW. "Memory processes in posttraumatic stress disorder". Awarded by:University of New South Wales. School of Psychology, 2006. http://handle.unsw.edu.au/1959.4/25206.
Testo completoAbstract (sommario):
Current theories of PTSD propose that impaired retrieval of trauma memories may impede processing of these memories and subsequent trauma recovery. This thesis investigated memory retrieval processes in trauma survivors with and without symptoms of posttraumatic stress, and in non-traumatised individuals exposed to a highly arousing event. Study 1 examined deliberate avoidance of unwanted memories in recent trauma survivors. The results indicated that attempts to forget were associated with poorer recall of forgotten information, but the size of this effect did not depend on the presence or absence of Acute Stress Disorder (ASD). Study 2 investigated automatic retrieval inhibition in trauma survivors with or without Posttraumatic Stress Disorder (PTSD). The results suggested that repeated retrieval of trauma-related information by individuals with PTSD can cause inhibition of related, but unpractised information. Studies 3 and 4 examined the relationship between the vantage point of trauma memories, avoidance and posttraumatic stress symptomatology. The findings indicated that recalling a traumatic event from an observer perspective is associated with post trauma avoidance. They also showed that an observer vantage point in the initial few weeks after trauma is associated with poorer long-term post trauma adjustment. Studies 5, 6 and 7 were analogue studies which analysed the impact of heightened arousal on memory retrieval in novice skydivers. The results suggested that elevated arousal can interfere with retrieval of information related to the arousal-inducing event. Study 7 also indicated that autobiographical memory for the event may be impaired. Finally, Study 8 examined the qualities of trauma memories that were accessed via different modes of retrieval. The results provided evidence that intrusive memories were experienced as more realistic and with more intense affect than memories for the same event that were deliberately retrieved. Together, the findings of this program of research extend current theories of PTSD by highlighting the mechanisms through which retrieval of trauma memories may be impaired. The results suggest that the quality of trauma memories is affected by avoidance processes, elevated arousal and level of conscious control the individual exerts over retrieval.
7
Kenny, Lucy Margaret. "Memory processes in posttraumatic stress disorder". [New South Wales : University of New South Wales], 2006. http://www.library.unsw.edu.au/~thesis/adt-NUN/uploads/approved/adt-NUN20061110.142022/public/02whole.pdf.
Testo completo
8
Damjanovic, Ljubica. "Memory processes in familiar voice recognition". Thesis, University of Essex, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413126.
Testo completo
9
Chou, C. "Psychophysiological processes involved in traumatic memory". Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1443289/.
Testo completoAbstract (sommario):
The pathways through which traumatic events are encoded into memory and subsequently retrieved affect the development of posttraumatic symptoms such as intrusion, as well as recovery from posttraumatic stress disorder (PTSD). This thesis examined how cardiovascular and hormonal processes are related to memory processing. Individual differences in traumatic history, as well as two cardiovascular stress response features, startle heart rate (sHR) and cardiac defence response (CDR), were investigated in this context as predictors and moderators. Relevant literature and the methods are reviewed in Chapter One and Chapter Two respectively. Chapter Three and Four adopted the trauma film paradigm to assess the memory encoding phase of trauma. The former found a dominant vagal activation during the analogue trauma, and identified a subgroup, in whom relationships between the psychological and physiological measures were different from the rest of the sample. The latter found increases in cortisol, and decreases in salivary alpha-amylase (sAA) levels, in response to the trauma film. Lower cortisol levels predicted greater vividness of intrusions. Individual differences in CDR and sAA levels moderated the relationship between cortisol and the frequency of intrusions. Chapters Five and Six examined PTSD patients’ psychological and physiological reactions to voluntary retrieval of traumatic memories. Significant relationships between HR decreases and overall negative psychological states were found in the former. Associations between greater dissociation and a smaller suppression of cortisol were found in the latter. An overall discussion regarding the psychological and physiological activities at the memory encoding and retrieval phases, as well as the roles of trauma history, sHR and CDR in moderating these responses, are presented in Chapter Seven.
10
Hwang, Soosung. "Essays on long memory processes and volatility". Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286421.
Testo completo
11
Parker, Andrew. "Conceptual processes in explicit and implicit memory". Thesis, Manchester Metropolitan University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340694.
Testo completo
12
Boldini, Angela. "Evidence for two processes in recognition memory". Thesis, University of Essex, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411203.
Testo completo
13
Banton, Louise J. "Cognitive processes and memory for piano music". Thesis, University of Leicester, 1994. http://hdl.handle.net/2381/34696.
Testo completoAbstract (sommario):
The research described in this thesis investigates the mental processes underlying the reading and recall of piano music. The first study examined memory for good and poor piano music as a function of sight-reading ability and different presentation and recall conditions. The findings indicated that whilst sight-reading accuracy had little effect on recall, sight-reading tempo was highly correlated with recall success. Good music was easier to recall than poor music, and written recall procedures generated greater recall success than played recall procedures. Played recall procedures were found to produce advantages for the immediate recall of music that had been sight-read during stimulus exposure. Written recall procedures produced significant long-term memory advantages, demonstrated by the greater preservation of structurally significant aspects of musical information over periods of extended memory storage. The second study explored the processes underlying memory for musical information by examining the strategies employed by musicians and non-musicians during the learning and written reproduction of scored piano music. The findings indicated that memory performances produced by musicians were superior to those produced by non-musicians and also improved at a faster rate of learning. Musicians were found to employ several knowledge-based music reading strategies that were unavailable to non-musicians, and to vary their reading strategies depending on the type of music that was being read. Although non-musicians were unaffected by the type of music presented to them, both subject groups were found to re-evaluate their use of reading strategies in light of previous recall performance success, and vary strategy employment in order to optimise recall success. The combined findings of these studies suggest that memory for musical information can be enhanced by the conditions surrounding information processing, and that the processes underlying the memory system are governed by highly flexible operations which reflect the degree of pre-existing knowledge possessed by an individual.
14
Gonen, Yaacovi G. "Encoding and retrieval processes in prospective memory". Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1344016/.
Testo completoAbstract (sommario):
The purpose of this thesis was to examine the influence of different characteristics of prospective memory (PM) cues and ongoing tasks on processes supporting PM retrieval. The first four experiments assessed the role of motivational enhancements on event- and timebased tasks. In the first experiment, it has been hypothesized that in a high-incentive condition, PM performance should be better compared with a low-incentive condition. In addition, in a negative reinforcement condition PM performance should be better than in a positive reinforcement condition. The second experiment extended these hypotheses by looking at individual differences, using skin conductance and personality questionnaires, while in the third experiment these hypotheses were used to assess order effect, using two successively low-incentive conditions. Finally, in the fourth experiment, these hypotheses have been tested on time-based PM tasks, including a punishment condition. The results from these experiments showed that high compared with low incentives influence retrieval processes on PM tasks. In addition, individuals differed in their performance to the negative and positive reinforcements on event-based tasks. Finally, performance was better under the punishment condition compared with the positive and negative reinforcement conditions on time-based tasks. The fifth experiment looked at how different types of PM cues and ongoing tasks influence retrieval processes when multiple cues were involved. Results showed that when the ongoing task was demanding and the PM cues were nonfocal, greater attentional resources were assigned to perform the PM task. In the final experiment, implicit and explicit encoding of PM intentions was investigated. It has been hypothesized that explicit encoding should lead to better performance compared with implicit encoding and that pre- and poststimulus neural activity, measured by electroencephalogram, will predict the retrieval of PM intentions. The overall results highlighted the influence of different components involved during encoding and retrieval of intentions, on PM performance.
15
Stewart, James Roosevelt Jr. "Memory and cognitive processes in childhood depression /". The Ohio State University, 1988. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487597424138804.
Testo completo
16
Clark, Michael. "Working Memory Processes in the Encoding of Intentions". Thesis, University of North Texas, 2004. https://digital.library.unt.edu/ark:/67531/metadc4629/.
Testo completoAbstract (sommario):
The primary interest of this investigation concerned working memory functioning and cue/act discrimination during encoding of intentions. The study included manipulations of working memory and intention load to investigate the encoding processes related to prospective memory (PM). Three experiments are presented that involve working memory distraction tasks at the time of encoding the PM intentions, as well as varying numbers of cues and actions. In the first experiment three cues were paired with one action, in the second, one cue with three actions, and in the third, three cues with three actions. Results suggest that the central executive is involved in binding a cue to an action, and that this operation is key to PM success. Furthermore, the phonological loop seems primarily involved with processing of cues and the visuospatial sketchpad with actions. It is further proposed that the processes of the phonological loop and visuospatial sketchpad must be successful before the central executive can bind the cues and acts together, which is possibly the most important part in the encoding of intentions. By directly examining PM at the time of encoding, information was gained that allows for a more complete understanding of the nature of how we form and execute intentions.
17
Kane, Kimberley Ann. "Electrophysiological indices of conscious and automatic memory processes". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ53859.pdf.
Testo completo
18
Paul, Matthew Arthur. "Object-based representations facilitate memory for inhibitory processes". Thesis, Bangor University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275165.
Testo completo
19
MacDonald, Ian. "Manual and verbal control processes in working memory". Thesis, Oxford Brookes University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363451.
Testo completo
20
Bablekou, Zoe. "Memory processes in children with specific language difficulties". Thesis, University of Leeds, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252961.
Testo completo
21
Berger, Barbara. "Brain oscillatory signatures of working memory control processes". Thesis, University of Surrey, 2015. http://epubs.surrey.ac.uk/807717/.
Testo completoAbstract (sommario):
Mnemonic operations are vital in our everyday life and comprise a vast array of sub-processes that need to be co-ordinated constantly to ensure smooth functioning. The goal of this work was to investigate the superimposed control component responsible for the co-ordination of those individual sub-processes. Furthermore, by using neuroscientific methods like electroencephalography (EEG) and transcranial magnetic stimulation (TMS), the underlying oscillatory signatures were explored and their behavioural relevance tested. It will be shown that increase in theta frequency (4-8 Hz) over medial frontal cortical areas is a local indicator of increasing task demand and task complexity. Moreover, findings will be presented that indicate that the phase of this local oscillation (frontal-midline theta, FMtheta) enables task-relevant processes in posterior cortical areas (represented by increased activity in the gamma frequency range, 30-80 Hz) to flexibly access prefrontal cognitive resources. This mechanism is implemented in a way that bursts of posterior gamma frequency are locked to specific phases of a FMtheta cycle. The higher the task complexity, i.e. the more prefrontal control processes are needed for its execution, the closer to the excitatory phase of FMtheta (trough) the posterior gamma bursts are nested. In contrast, when only very little cognitive control needs to be employed, the posterior fast frequency bursts are locked near the inhibitory FMtheta phase (peak) rather. By using repetitiveTMS it was furthermore possible to show the behavioural relevance of this mechanism and how the disruption thereof has a highly selective and immediate deteriorating effect on working memory performance. Moreover, it will be demonstrated that this mechanism does not only depend on task difficulty but can be influenced and controlled voluntarily by information prioritisation. Finally, based on these findings a model will be introduced that could potentially explain the mechanism of such flexible allocation of and access to prefrontal control processes.
22
Robinson, Lianne. "Cannabinoid involvement in spatial learning and memory processes". Thesis, University of Aberdeen, 2004. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU193926.
Testo completoAbstract (sommario):
Previous studies have revealed that cannabinoids have detrimental effects on learning and memory in humans and animals. Infusion of the exogenous Cannabinoid agonists including D9-tetrahydrocannabinol (D9-THC), HU210 and WIN-55, 212-2 (WIN-2) in animals has consistently been shown to induce deficits in spatial learning and memory. CB1 receptors are evident in the hippocampus and prefrontal cortex; brain areas involved in spatial learning and memory processes. The main aim of this study was to determine the mechanisms underlying these Cannabinoid-induced effects on spatial learning and memory. Lister Hooded rats were used to study the effects of cannabinoids in a sequence of experiments using the water maze. A novel paradigm to test place preference in the water maze was developed and it was revealed that D9-THC induced place aversion whereas WIN-2 had no effect. These aversive properties of D9-THC along with the non-spatial, non-CB1receptor effects of HU210 in reference memory may confound the results obtained for spatial learning and memory. By contrast, WIN-2 deficits would be a genuine result of spatial impairments. WIN-2 induced differential effects on working and reference memory. Reversal with the CB1 antagonist AM281 and vanilloid receptor (VR1) antagonist Iodo-RTX suggest that the WIN-2 effects are mediated via a non-CB 1/non-VR1 receptor located in the hippocampus. The WIN-2 effects could also be mediated via a possible interaction with the cholinergic system, as the cholinesterase inhibitor Rivastigmine was able to reverse the deficit. In addition to exogenous cannabinoids, using the CB1 antagonist SR141716A (SR) observed that endocannabinoids also impaired spatial learning and memory, with SR acting like an inverse agonist. In conclusion both cannabinoids and endocannabinoids impair spatial learning and memory in the water maze, and these deficits may occur via interactions with other neurotransmitter systems. However, whether these actions are mediated via the CB1 or a non-CB1 mechanism still remains unclear.
23
Mill, Ravi Dev. "Strategic control processes in episodic memory and beyond". Thesis, University of St Andrews, 2015. http://hdl.handle.net/10023/11344.
Testo completoAbstract (sommario):
The evaluation of past experience is influenced both by the strength of retrieved memories and factors in the immediate retrieval environment, including emphasised goals and cued expectations. However, the laboratory study of episodic memory has neglected such environmental influences, despite their overt contribution to real- world decision outcomes. The aim of this PhD thesis was to rectify this neglect, and clarify the interaction of memory evidence and environmental strategies in the service of strategic memory control. A related aim was to investigate whether control processes identified in the isolated domain of episodic memory in fact performed a more general or “cross-domain” function. An initial series of behavioural experiments (Experiments 1-3) elucidated an overlooked source of strategic bias in the standard recognition environment –implicit goal emphasis imparted by question format. Experiment 4 investigated whether the question bias was commonly enacted across different domains of evaluation, yielding modest evidence in favour of this underlying cross-domain function. Experiment 5 instantiated more explicit manipulation of goal emphasis and cued expectation, and recovered independent and opposing strategic effects of these two environmental factors, emerging across episodic and non-episodic domains. Experiment 6 employed a simultaneous EEG-fMRI approach to elucidate the neural correlates of memory control, identifying a modulation of the late positive event- related potential during the resolution of mnemonic conflict, which was sourced to BOLD variation in regions of the rostral cingulate zone and intraparietal sulcus. Experiment 7 used pupillometry to examine pupil-linked autonomic systems that have also been implicated in memory control, and isolated two distinct components of the dilation response evoked during environmental conflict –an “early amplitude” unexpected familiarity effect and a “trailing slope” uncertainty effect. The findings illuminate the cross-domain underpinnings of an adaptive memory control system, evidenced in behaviour and across different functional neuroimaging modalities, and across episodic and non-episodic domains of evaluation.
24
Hoffmann, Salvaña Xavier Roderic. "Memory-induced complex contagion in spreading phenomena on networks". Doctoral thesis, Universitat de Barcelona, 2021. http://hdl.handle.net/10803/672674.
Testo completoAbstract (sommario):
Epidemic modeling has proven to be an essential framework for the study of contagion phenomena in biological, social, and technical systems. Albeit epidemic models have evolved into powerful predictive tools, most assume memoryless agents and independent transmission channels. Nevertheless, many real-life examples are manifestly time-sensitive and show strong correlations. Moreover, recent trends in agent-based modeling support a generalized shift from edge-based descriptions toward node-centric approaches.
Here I develop an infection mechanism that is endowed with memory of past exposures and simultaneously incorporates the joint effect of multiple infectious sources. A notion of social reinforcement/inhibition arises organically, without being incorporated explicitly into the model. As a result, the concepts of non-Markovian dynamics and complex contagion become intrinsically coupled. I derive mean-field approximations for random degree-regular networks and perform extensive stochastic simulations for nonhomogeneous networks.
The analysis of the SIS model reveals a sophisticated interplay between two memory modes, displayed by a collective memory loss and the dislocation of the critical point into two phase transitions. An intermediate region emerges where the system is either excitable or bistable, exhibiting fundamentally distinct behaviors compared to the customary healthy and endemic phases. Additionally, the transition to the endemic phase becomes hybrid, showing both continuous and discontinuous properties.
These results provide renewed insights on the interaction between microscopic mechanisms and topological aspects of the underlying contact networks, and their joint effect on the properties of spreading processes. In particular, this type of modeling approach that combines memory effects and complex contagion could be suitable to describe ecological interactions between biological and social pathogens.El modelatge epidèmic ha demostrat ser un marc essencial per a l’estudi dels fenòmens de contagi en sistemes biològics, socials i tècnics. Tot i que els models epidèmics han evolucionat cap a potents eines de predicció, la majoria assumeixen agents sense memòria i canals de transmissió independents. No obstant això, molts exemples de la vida real mostren fortes correlacions temporals i estructurals. A més, les tendències recents en la modelització basada en agents donen suport a un canvi generalitzat de les descripcions basades en els enllaços cap a enfocaments on els nodes són centrals. Aquí desenvolupo un mecanisme d’infecció dotat de memòria a exposicions passades i que simultàniament incorpora l’efecte conjunt de múltiples fonts infeccioses. Una noció de reforç/inhibició social sorgeix de manera orgànica, sense incorporar-se explícitament al model. Com a resultat, els conceptes de dinàmica no markoviana i contagi complex s’acoblen intrínsecament. Derivo aproximacions de camp mitjà per a xarxes aleatòries de grau fix i realitzo extenses simulacions estocàstiques per a xarxes no homogènies. L'anàlisi del model SIS revela una interacció sofisticada entre dos modes de memòria, que es manifesta mitjançant una pèrdua de memòria col·lectiva i la dislocació del punt crític en dues transicions de fase. Apareix una regió intermitja on el sistema és excitable o bistable, amb comportaments fonamentalment diferents en comparació amb les fases sanes i endèmiques habituals. A més, la transició a la fase endèmica esdevé híbrida, mostrant propietats contínues i també discontínues. Aquests resultats proporcionen una visió renovada sobre la interacció entre mecanismes microscòpics i aspectes topològics de les xarxes de contacte subjacents, i el seu efecte conjunt sobre les propietats dels processos de propagació. En particular, aquest tipus de modelització que combina efectes de memòria i contagi complex podria ser adequat per descriure interaccions ecològiques entre patògens biològics i socials.
El modelado epidémico ha demostrado ser un marco esencial para el estudio de los fenómenos de contagio en sistemas biológicos, sociales y técnicos. Aunque los modelos epidémicos han evolucionado hacia potentes herramientas de predicción, la mayoría asumen agentes sin memoria y canales de transmisión independientes. Sin embargo, muchos ejemplos de la vida real muestran fuertes correlaciones temporales y estructurales. Además, las tendencias recientes en la modelización basada en agentes apoyan un cambio generalizado de las descripciones basadas en los enlaces hacia enfoques donde los nodos son centrales.Aquí desarrollo un mecanismo de infección dotado de memoria a exposiciones pasadas y que simultáneamente incorpora el efecto conjunto de múltiples fuentes infecciosas. Una noción de refuerzo/inhibición social surge de manera orgánica, sin incorporarse explícitamente al modelo. Como resultado, los conceptos de dinámica no Markoviana y contagio complejo se acoplan intrínsecamente. Derivo aproximaciones de campo medio para redes aleatorias de grado fijo y realizo extensas simulaciones estocásticas para redes no homogéneas.El análisis del modelo SIS revela una interacción sofisticada entre dos modos de memoria, que se manifiesta mediante una pérdida de memoria colectiva y la dislocación del punto crítico en dos transiciones de fase. Aparece una región intermedia donde el sistema es excitable o bistable, con comportamientos fundamentalmente diferentes en comparación con las fases sanas y endémicas habituales. Además, la transición a la fase endémica se convierte en híbrida, mostrando propiedades continuas y también discontinuas.Estos resultados proporcionan una visión renovada sobre la interacción entre mecanismos microscópicos y aspectos topológicos de las redes de contacto subyacentes, y su efecto conjunto sobre las propiedades de los procesos de propagación. En particular, este tipo de modelización que combina efectos de memoria y contagio complejo podría ser adecuado para describir interacciones ecológicas entre patógenos biológicos y sociales.
25
Jones, Kelly M. "Self -efficacy, memory, and identity processes in older adults". Amherst, Mass. : University of Massachusetts Amherst, 2009. http://scholarworks.umass.edu/dissertations/AAI3379972/.
Testo completo
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Kolodny, Jonathan Avram. "Conscious and unconscious processes in learning and memory retrieval". Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241583.
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27
McGann, Deborah. "Prospective memory : processes and the influence of divided attention". Thesis, University of Reading, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265626.
Testo completo
28
Zhu, Beijia. "Analysis of non-stationary (seasonal/cyclical) long memory processes". Thesis, Paris 1, 2013. http://www.theses.fr/2013PA010013/document.
Testo completoAbstract (sommario):
La mémoire longue, aussi appelée la dépendance à long terme (LRD), est couramment détectée dans l’analyse de séries chronologiques dans de nombreux domaines, par exemple,en finance, en économétrie, en hydrologie, etc. Donc l’étude des séries temporelles à mémoire longue est d’une grande valeur. L’introduction du processus ARFIMA (fractionally autoregressive integrated moving average) établit une relation entre l’intégration fractionnaire et la mémoire longue, et ce modèle a trouvé son pouvoir de prévision à long terme, d’où il est devenu l’un des modèles à mémoire longue plus populaires dans la littérature statistique. Précisément, un processus à longue mémoire ARFIMA (p, d, q) est défini comme suit : Φ(B)(I − B)d (Xt − µ) = Θ(B)εt, t ∈ Z, où Φ(z) = 1 − ϕ1z − · · · − ϕpzp et Θ(z) = 1 + · · · + θ1zθpzq sont des polynômes d’ordre p et q, respectivement, avec des racines en dehors du cercle unité; εt est un bruit blanc Gaussien avec une variance constante σ2ε. Lorsque d ∈ (−1/2,1/2), {Xt} est stationnaire et inversible. Cependant, l’hypothèse a priori de la stationnarité des données réelles n’est pas raisonnable. Par conséquent, de nombreux auteurs ont fait leurs efforts pour proposer des estimateurs applicables au cas non-stationnaire. Ensuite, quelques questions se lèvent : quel estimateurs doit être choisi pour applications, et à quoi on doit faire attention lors de l’utilisation de ces estimateurs. Donc à l’aide de la simulation de Monte Carlo à échantillon fini, nous effectuons une comparaison complète des estimateurs semi-paramétriques, y compris les estimateurs de Fourier et les estimateurs d’ondelettes, dans le cadre des séries non-stationnaires. À la suite de cette étude comparative, nous avons que (i) sans bonnes échelles taillées, les estimateurs d’ondelettes sont fortement biaisés et ils ont généralement une performance inférieure à ceux de Fourier; (ii) tous les estimateurs étudiés sont robustes à la présence d’une tendance linéaire en temps dans le niveau de {Xt} et des effets GARCH dans la variance de {Xt}; (iii) dans une situation où le probabilité de transition est bas, la consistance des estimateurs quand même tient aux changements de régime dans le niveau de {Xt}, mais les changements ont une contamination au résultat d’estimation; encore, l’estimateur d’ondelettes de log-regression fonctionne mal dans ce cas; et (iv) en général, l’estimateur complètement étendu de Whittle avec un polynôme locale (fully-extended local polynomial Whittle Fourier estimator) est préféré pour une utilisation pratique, et cet estimateur nécessite une bande (i.e. un nombre de fréquences utilisés dans l’estimation) plus grande que les autres estimateurs de Fourier considérés dans ces travauxLong memory, also called long range dependence (LRD), is commonly detected in the analysis of real-life time series data in many areas; for example, in finance, in econometrics, in hydrology, etc. Therefore the study of long-memory time series is of great value. The introduction of ARFIMA (fractionally autoregressive integrated moving average) process established a relationship between the fractional integration and long memory, and this model has found its power in long-term forecasting, hence it has become one of the most popular long-memory models in the statistical literature. Specifically, an ARFIMA(p,d,q) process X, is defined as follows: cD(B)(I - B)d X, = 8(B)c, , where cD(z)=l-~lz-•••-~pzP and 8(z)=1-B1z- .. •-Bqzq are polynomials of order $p$ and $q$, respectively, with roots outside the unit circle; and c, is Gaussian white noise with a constant variance a2 . When c" X, is stationary and invertible. However, the a priori assumption on stationarity of real-life data is not reasonable. Therefore many statisticians have made their efforts to propose estimators applicable to the non-stationary case. Then questions arise that which estimator should be chosen for applications; and what we should pay attention to when using these estimators. Therefore we make a comprehensive finite sample comparison of semi-parametric Fourier and wavelet estimators under the non-stationary ARFIMA setting. ln light of this comparison study, we have that (i) without proper scale trimming the wavelet estimators are heavily biased and the y generally have an inferior performance to the Fourier ones; (ii) ail the estimators under investigation are robust to the presence of a linear time trend in levels of XI and the GARCH effects in variance of XI; (iii) the consistency of the estimators still holds in the presence of regime switches in levels of XI , however, it tangibly contaminates the estimation results. Moreover, the log-regression wavelet estimator works badly in this situation with small and medium sample sizes; and (iv) fully-extended local polynomial Whittle Fourier (fextLPWF) estimator is preferred for a practical utilization, and the fextLPWF estimator requires a wider bandwidth than the other Fourier estimators
29
Moro, R. "Control and maintenance processes in working memory : neuropsychological investigations". Thesis, University College London (University of London), 2008. http://discovery.ucl.ac.uk/1444462/.
Testo completoAbstract (sommario):
The aim of this thesis was to investigate working memory by investigating performance on an updating task devised to pose variable demands on maintenance and control processes. The task required participants to recall information that was "relevant" according to a given criterion, at the same time inhibiting information that was not relevant to that criterion. Performance on this task was investigated in healthy participants, in order to understand the impact of different loads on maintenance and inhibition processes, and of different stimuli on recall performance and on error production. The predictions tested were that recall performance on the updating task would be affected by both load on maintenance and load on control processes and that the production of errors due to the recall of "to-be-inhibited" information would only be affected by load on control processes. The hypothesis that the central executive component of working memory would be differentially affected by normal aging, dementia of the Alzheimer's type and brain damage affecting the prefrontal lobes was also explored by investigating performance on the updating task in groups with these characteristics. The predictions were that in normal ageing maintenance would be reduced but control processes would be spared, in senile dementia both processes would be impaired and in presence of prefrontal damage only control processes would be affected. Moreover, since the multi-component model of working memory was originally conceived as the basis for complex cognitive abilities such as mental arithmetic, this was also investigated in groups of participants reported in the literature as having problems in these functions as well as in working memory. The findings are discussed in light of the predictions.
30
Ring, Melanie. "Relational memory processes in adults with autism spectrum disorder". Thesis, City, University of London, 2017. http://openaccess.city.ac.uk/17002/.
Testo completoAbstract (sommario):
Research on memory in Autism Spectrum Disorder (ASD) points to difficulties in memory for personal experiences (episodic memory - EM). In particular, difficulties were found for the processing of relations between units of material leaving memory for single items mostly intact. The aim of this thesis was to examine EM in ASD further by investigating the influence of meaning, type of material, and relations, and by assessing the influence of complexity, executive functions, and attention on memory, learning, and spatial navigation in ASD. In addition to memory behaviour, eye movements were measured. It was found that the EM impairment in ASD adults with average intellectual abilities persisted across a range of materials and types of relations, and that item memory was also affected when using tests of similar complexity to relational memory tests. Eye movements indicated attentional differences in ASD that may have had an impact on the observed difficulties, and they indicated that memory difficulties went beyond explicit deliberate retrieval of information also affecting implicit memory and, therefore, suggesting that also encoding and postencoding processes may work differently in ASD. Spatial navigation was particularly affected by executive function and item memory difficulties in ASD, and structural learning may be the fundamental mechanism that underlies the cognitive difficulties observed in ASD. Future research should concern the development and application of measures for less verbal and/or intellectually able ASD individuals and the investigation of how the studied processes are affected by ageing in the ASD population. In addition, training and support strategies should be developed to investigate whether memory difficulties in ASD are caused by a processing bias or a deficit and to attempt to alleviate them. Finally, the investigation of memory encoding and consolidation is needed to test whether these processes operate differently in ASD and, if so, how they could be improved.
31
Mudelsee, Manfred. "Long memory and the aggregation of AR(1) processes". Universität Leipzig, 2006. https://ul.qucosa.de/id/qucosa%3A15498.
Testo completoAbstract (sommario):
Granger (1980) found that the aggregation of m short-memory AR(1) processes yields a long-memory process. Thereby he assumed m -> ∞, Gaussian shape and betadistributed AR(1) parameters over (0; 1). To test hypotheses that long memory in climate time series comes from aggregation, the finding of Granger (1980) cannot be directly applied. First, the number of \'microclimatic\' processes to be aggregated is finite. Second, climatic processes often produce right-skewed data. Third, the AR(1) parameters of the microclimatic processes could be restricted to a narrower interval than (0; 1). We
therefore perform Monte Carlo simulations to study aggregation in climate time series under realistic conditions. The long-memory parameter, H, is estimated by fitting an ARFIMA model to various types of aggregations. Our results are as follows. First, for m above a few hundred, H approaches saturation. Second, the distributional shape has little influence, as noted by Granger (1980). Third, the upper limit of the interval for the AR(1) parameter has a strong influence on the saturation value of H, as noted by Granger (1980).Granger (1980) fand heraus, dass die Summe von m schwach seriell abhängigen AR(1)-Prozessen einen stark seriell abhängigen Prozess ergibt. Er nahm dabei an, dass m -> ∞ geht, die Verteilungen Gaußsch sind und die AR(1)-Parameter beta-verteilt über (0; 1) sind. Um die Hypothese zu testen, daß starke serielle Abhängigkeit in Klimazeitreihen von dieser \'Aggregation\' rührt, kann das Ergebnis von Granger (1980) jedoch nicht direkt angewendet werden. Erstens: die Anzahl \'mikroklimatischer\', zu summierender Prozesse is endlich. Zweitens: Klimaprozesse erzeugen oft rechtsschief verteilte Daten. Drittens: die AR(1)-Parameter der mikroklimatischen Prozesse mögen auf ein engeres Intervall begrenzt sein als (0; 1). Wir f¨uhren deshalb Monte-Carlo-Simulationen durch, um die Aggregation in Klimazeitreihen für realistische Bedingungen zu studieren. Der Parameter H, der die starke serielle Abhängigkeit beschreibt, wird geschätzt durch die Anpassung eines ARFIMA-Modelles an unterschiedliche Aggregations-Typen. Unsere Ergebnisse sind wie folgt. Erstens: für m oberhalb einiger hundert erreicht H S¨attigung. Zweitens: die Verteilungsform hat geringen Einfluß, wie von Granger (1980) bemerkt. Drittens: die obere Grenze des Intervalles für den AR(1)-Parameter hat einen starken Einfluß auf den Sättigungwert von H, wie von Granger (1980) bemerkt.
32
Mudelsee, Manfred. "Long memory and the aggregation of AR(1) processes". Universitätsbibliothek Leipzig, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-222017.
Testo completoAbstract (sommario):
Granger (1980) found that the aggregation of m short-memory AR(1) processes yields a long-memory process. Thereby he assumed m -> ∞, Gaussian shape and betadistributed AR(1) parameters over (0; 1). To test hypotheses that long memory in climate time series comes from aggregation, the finding of Granger (1980) cannot be directly applied. First, the number of \"microclimatic\" processes to be aggregated is finite. Second, climatic processes often produce right-skewed data. Third, the AR(1) parameters of the microclimatic processes could be restricted to a narrower interval than (0; 1). We therefore perform Monte Carlo simulations to study aggregation in climate time series under realistic conditions. The long-memory parameter, H, is estimated by fitting an ARFIMA model to various types of aggregations. Our results are as follows. First, for m above a few hundred, H approaches saturation. Second, the distributional shape has little influence, as noted by Granger (1980). Third, the upper limit of the interval for the AR(1) parameter has a strong influence on the saturation value of H, as noted by Granger (1980)Granger (1980) fand heraus, dass die Summe von m schwach seriell abhängigen AR(1)-Prozessen einen stark seriell abhängigen Prozess ergibt. Er nahm dabei an, dass m -> ∞ geht, die Verteilungen Gaußsch sind und die AR(1)-Parameter beta-verteilt über (0; 1) sind. Um die Hypothese zu testen, daß starke serielle Abhängigkeit in Klimazeitreihen von dieser \"Aggregation\" rührt, kann das Ergebnis von Granger (1980) jedoch nicht direkt angewendet werden. Erstens: die Anzahl \"mikroklimatischer\", zu summierender Prozesse is endlich. Zweitens: Klimaprozesse erzeugen oft rechtsschief verteilte Daten. Drittens: die AR(1)-Parameter der mikroklimatischen Prozesse mögen auf ein engeres Intervall begrenzt sein als (0; 1). Wir f¨uhren deshalb Monte-Carlo-Simulationen durch, um die Aggregation in Klimazeitreihen für realistische Bedingungen zu studieren. Der Parameter H, der die starke serielle Abhängigkeit beschreibt, wird geschätzt durch die Anpassung eines ARFIMA-Modelles an unterschiedliche Aggregations-Typen. Unsere Ergebnisse sind wie folgt. Erstens: für m oberhalb einiger hundert erreicht H S¨attigung. Zweitens: die Verteilungsform hat geringen Einfluß, wie von Granger (1980) bemerkt. Drittens: die obere Grenze des Intervalles für den AR(1)-Parameter hat einen starken Einfluß auf den Sättigungwert von H, wie von Granger (1980) bemerkt
33
Rudkin, Susan. "Executive processes in visual and spatial working memory tasks". Thesis, University of Aberdeen, 2001. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU140973.
Testo completoAbstract (sommario):
The main aim of the thesis was to investigate the nature of the cognitive mechanisms which underlie performance on specific visuo-spatial working memory tasks, with the emphasis on exploring the extent of central executive involvement. This research began with an attempt to investigate performance on two standard visual and spatial tasks in a small sample of mild-to-moderate AD patients, and compare this with performance on two adapted versions of the tasks (Experiments 1 & 2). The tasks were adapted to increase the ecological validity, but this adaptation appeared to alter the demands of the tasks, which prevented their further investigation as useful alternatives. The following experiments concentrated on investigating visual and spatial working memory in healthy populations. Experiments 3, 4, 5 and 6 employed a dual-task paradigm, whereby specific visual and spatial working memory tasks were combined with tasks assumed to involve executive processes. Experiments 3, 4 and 5 employed oral random digit generation as an executive task. The results of Experiments 3 and 5 indicated that visuo-spatial tasks which involve sequential processing show more interference with random digit generation than visuo-spatial tasks which involve simultaneous processing. The findings of Experiment 4 suggested that, when both item and order information are presented (i.e. with sequential presentation), subsequent recall or visuo-spatial material is attention demanding regardless of whether item only, order only, or both item and order information are required in response. These findings appear to indicate that visuo-spatial tasks which involve sequential processing require executive resources to a greater extent than visuo-spatial tasks which involve simultaneous processing. However, oral random generation is a sequential task, and requires the maintenance of serial order (in order to produce a random sequence). Therefore an alternative interpretation could be that the sequential nature of the oral random generation task gave rise to the pattern of selective impairment on sequential visuo-spatial tasks, rather than more general executive load.
34
Craigmile, Peter Francis. "Wavelet-based estimation for trend contaminated long memory processes /". Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/8967.
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35
Lusena, Christopher. "Finite memory policies for partially observable Markov decision processes". Lexington, Ky. : [University of Kentucky Libraries], 2001. http://lib.uky.edu/ETD/ukycosc2001d00021/lusena01.pdf.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Kentucky, 2001.Title from document title page. Document formatted into pages; contains viii, 89 p. : ill. Includes abstract. Includes bibliographical references (p. 81-86).
36
Misiran, Masnita. "Modeling and pricing financial assets under long memory processes". Thesis, Curtin University, 2010. http://hdl.handle.net/20.500.11937/2549.
Testo completoAbstract (sommario):
An important research area in financial mathematics is the study of long memory phenomenon in financial data. Long memory had been known long before suitable stochastic models were developed. Fractional Brownian motion (FBM) can be used to characterize this phenomenon. This thesis examines the use of FBM and its long memory parameter H, from the view point of estimation method, approximation, and numerical performance.How to estimate the long memory parameter H is important in financial pricing. This thesis starts by reviewing the performance of some existing preliminary methods for estimating H. It is then applied to some Malaysia financial data. Although these methods are easy to use, their performance are in doubts, in particular these methods can only get an estimator of H, without providing the dynamic, long-memory behaviour of financial price process.This thesis is therefore concerned with the estimation of the dynamic, long-memory behaviour of financial processes. We propose estimation methods based on models of two stochastic differential equations (SDEs) perturbed by FBM, that play important role in option pricing and interest rate modelling. These models are the geometric fractional Brownian motion (GFBM) and the fractional Ornstein-Uhlenbeck (FOU) model, respectively. These methods are able to obtain H and other parameters involved in the models. The efficiency of these methods are investigated through simulation study. We applied the new methods to some financial problems.We also extend this study to filtering the SDE driven by FBM in multidimensional case. We propose a novel approximation scheme to this problem. The convergence property is also established. The performance of this method is evaluated through solving some numerical examples. Results demonstrate that methods developed in this thesis are applicable and have advantages when compared with other existing approaches.
37
Marklund, Petter. "Shared component processes in working memory and long-term memory : Insights from functional brain imaging". Licentiate thesis, Umeå University, Department of Psychology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-14731.
Testo completoAbstract (sommario):
Marklund, P. (2004). Shared component processes in working memory and long-term memory: Insights from functional brain imaging. Department of Psychology, Umeå University, S-901 87 Umeå SwedenRecent findings from functional neuroimaging studies have shown pronounced similarities in the functional brain activity patterns associated with tests of various cognitive functions. This thesis investigates shared component processes in working memory and declarative long-term memory. Study 1 showed a common pattern of increased activity in four anatomically distinct regions in prefrontal cortex during three tests each of working memory, episodic memory, and semantic memory. Such similarities may reflect shared demands on working-memory processes across all tests or increased demands on attentional mechanisms. Study 2 was designed to dissociate these possibilities by measuring sustained and transient brain activity during tests of working memory, long-term memory and sustained attention. The results provided support for the notion that one basis for overlapping activations is increased attentional demands, but some activity seems to reflect cognitive control related to mnemonic processes. Taken together, the results indicate that it is critical for taxonomies of cognitive functions to consider similarities in underlying cognitive and associated neurobiological component processes.
38
Ao, Xue. "Study of fluctuations in gene regulation circuits with memory". HKBU Institutional Repository, 2012. https://repository.hkbu.edu.hk/etd_ra/1428.
Testo completo
39
Griffiths, Alexander Ivor. "Retrieval processes in social identification". Thesis, University of St Andrews, 2015. http://hdl.handle.net/10023/6956.
Testo completoAbstract (sommario):
The utility of selective retrieval processes in our everyday lives is evident across the varied contexts we are subjected to as human beings. Memory is characterised by an unlimited storage capacity, but limited retrieval capacity. Subsequently, we are selective in what we remember in a given context in order to use memory in an adaptive manner. Previous theory places memory at the centre of deriving and maintaining a sense of self and personal identity. In contrast however, the extent to which memory serves the representation of social identities and the groups to which they are linked is unclear. As social identities are said to be the extension of the self to the social context, the present empirical investigation examined the role of selective processes of retrieval and forgetting on the remembrance of social identity and group-based information in the areas of gender, religious, partisan, and ideological identity. Findings illustrated that we implicitly preserve and retrieve information that is relevant to our sense of social identity, whilst forgetting and implicitly diminishing information that is irrelevant. The findings also established that information retrieved not only pertains to the in-groups in which we seek membership, but also of opposing out-groups that seek to contrast and potentially challenge our in-group's worldview. Furthermore, mechanisms and structures that support the representation of self were extended to the findings, delineating how processes of organisational and distinctive processing support the retrieval of social identity-based information of relevance and importance. The thesis concludes with the assertion that memory is not only the looking glass through which we see the reflection of the self, but also serves to act as the reflection through which we acquaint ourselves with, and relate ourselves to, our significant others in the social context.
40
Persson, Bjorn Martin. "Cognitive and neural processes underlying memory for time and context". Thesis, University of St Andrews, 2017. http://hdl.handle.net/10023/11024.
Testo completoAbstract (sommario):
The aim of this thesis is to examine the underlying cognitive and neural processes at play during retrieval of temporal and contextual source information. This was assessed across three experimental chapters. In the first experimental chapter, Chapter 2, the neural loci of context associations were assessed. Rats trained on an odour-context association task were given lesions to either the Lateral Entorhinal Cortex (LEC) or sham lesions. After surgery, performance on the odour-context task was assessed. It was hypothesised that memory for previously learned odour-context associations would be impaired following LEC lesions but not sham lesions. The results supported this hypothesis, demonstrating impaired memory for the previously learned odour-context associations in the LEC lesion group compared to the Sham lesion. In Chapter 3, the underlying retrieval processes used to retrieve time and context in human memory was assessed across three experiments. It was hypothesised that time would be remembered accurately using both recollection and familiarity, while correct context memory should rely on recollection alone. Two out of the three experiments supported this hypothesis, demonstrating that temporal information can be retrieved using familiarity in certain instances. The final experimental Chapter 4 used fMRI to extend Chapter 3 and examine whether neural activity would be greater in regions associated with recollection during memory for context, while activity in familiarity-related regions would be higher during memory for time. Results revealed no support for these predictions with no regions linked to recollection showing greater context-related activity, and no regions previously linked to familiarity exhibiting increased activation as temporal information was retrieved. The results are discussed in relation to established recollection and familiarity frameworks and previous work examining the neural substrates supporting memory for time and context.
41
Gitelman, Julian. "Synaptic incorporation of GluA1-containing AMPA receptors during memory processes". Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=110505.
Testo completoAbstract (sommario):
It is generally understood that modifications in synaptic strength are the basis for learning and memory and that the strength of a synapse is largely governed by the abundance and distribution of synaptic receptors, especially alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptors (AMPA receptors), which mediate most of the fast synaptic transmission in the brain. GluA1-containing AMPARs are incorporated into the synapse following activity and posttranslational modifications to the carboxyl-terminus affect which proteins interact with the receptor and determine whether the receptor is inserted or removed from the synapse. In vitro research has discovered that the phosphorylation of three serine residues contained on the carboxyl-terminus (Ser 818, Ser-831 and Ser-845) regulates GluA1 synaptic incorporation; however, in vivo research investigating the relative importance of these phosphorylation sites on long-term memory formation is currently limited to knock in studies.To block the interactions between these phosphorylation sites and their binding partners in an inducible, temporally sensitive manner, we infused interference peptides containing these residues during consolidation and reconsolidation. We hypothesized that if the synaptic incorporation of GluA1 containing AMPA receptors is required for memory formation, and if this incorporation required the residues contained on the interference peptide, we would see an impairment in long-term memory expression when the peptide was infused at the time of training, or at the time of retrieval.Infusing the interference peptide GluA1-CT, containing Ser-831 and Ser 845, 1 hour before auditory fear conditioning produced no impairment in memory expression 24 hours later. However, infusing the interference peptide GluA1-MPR, containing Ser-818, 1 hour before training did produce an impairment in memory expression 24 hours later. We did not observe an impairment in long-term memory expression when both peptides were infused 1 hour before memory reactivation.Il est généralement accepté que les modifications de la force synaptique sont à la base de l'apprentissage et la mémoire et que la force d'une synapse est largement régie par l'abondance et la distribution de récepteurs synaptiques, en particulier de récepteurs alpha-amino-3-hydroxy-5-méthyl-4- isoxazole propionate (récepteurs AMPA), qui interviennent dans la plupart des transmissions synaptiques rapides dans le cerveau. Les récepteurs AMPA contenant la sous-unité GluA1 sont incorporés dans la synapse suite à son activation et des modifications post-traductionnelles de l'extrémité carboxy-terminale influencent quelles protéines interagissent avec le récepteur et détermine si le récepteur est inséré ou retiré de la synapse. Des recherches in vitro ont découvert que la phosphorylation de trois résidus sérine contenus sur l'extrémité carboxy-terminale (Ser-818, Ser-831 et Ser-845) régie l'incorporation synaptique de GluA1; cependant, les recherches in vivo étudiant l'importance de ces sites de phosphorylation sur la formation de la mémoire à long terme est actuellement limitée à des études utilisant des « knock in ». Pour bloquer les interactions entre ces sites de phosphorylation et de leurs partenaires de liaison de manière inductible et temporellement sensibles, nous avons infusé des peptides d'interférence contenant ces résidus lors de la consolidation et la reconsolidation. Nous émettons l'hypothèse que si l'incorporation synaptique des récepteurs AMPA contenant GluA1 est nécessaire à la formation de la mémoire, et si cette incorporation exige les résidus contenus dans le peptide d'interférence, nous verrions une déficience dans l'expression de mémoire à long terme lorsque le peptide a été infusé au moment du conditionnement ou du rappel du souvenir.L'infusion du peptide d'interférence GluA1-CT, contenant les sérines Ser 831 et Ser-845, 1 heure avant le conditionnement de peur auditive n'a produit aucune altération dans l'expression de mémoire 24 heures plus tard. Cependant, l'infusion du peptide d'interférence GluA1-MPR, contenant la sérine Ser-818, 1 heure avant le conditionnement a produit une déficience dans l'expression de mémoire 24 heures plus tard. Nous n'avons pas observé d'altération dans l'expression de mémoire à long terme lorsque les deux peptides ont été infusés 1 heure avant la réactivation.
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Molina, Andres Antonio Haye. "Collective memory : an investigation into its cognitive and group processes". Thesis, University of Sheffield, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289656.
Testo completo
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Graves, Timothy. "A systematic approach to Bayesian inference for long memory processes". Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608183.
Testo completo
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Margrove, Kerrie L. "Investigation into the memory processes that underlie judgments of recency". Thesis, Cardiff University, 2009. http://orca.cf.ac.uk/54838/.
Testo completoAbstract (sommario):
Judgements of recency (JORs) are decisions about how long ago a repeated item was initially presented. Event-related potentials (ERPs) were acquired in three experiments, alongside behavioural measures, in order to determine the number and nature of memory processes contributing to JORs. In a series of continuous verbal memory tasks (adapted from Yntema & Trask, 1963), participants were presented with a long list of words and for each item participants were required to make an old/new recognition judgement, followed by a numerical JOR. The repetition intervals and JOR response options varied across experiments from between 5 to 35 intervening words. The mid-frontal old/new effect and the left parietal old/new effect were two ERP modulations which varied in a strength-based manner across time and JOR. These bore resemblances to effects reported in previous studies where they were associated with familiarity and recollection memory processes respectively. Late frontal ERP activity was also identified in the experiments and this is discussed in relation to previous theory. A series of behavioural experiments was employed in addition to the ERP studies, which also involved continuous memory tasks. These studies all had 6 different repetition lags and JOR response options which were between 5 and 30 with increments of 5 (adapted from Hintzman, 2003). This research was conducted in order to address further questions about how recollection and familiarity might support JORs under different circumstances. Additional support for the notion that memory processes underpin JORs in a strength-based manner was identified in this behavioural series. The findings in this thesis therefore suggest that JORs are based in part on an assessment of memory strength, and that two memory processes are likely to support memory for recency under some circumstances.
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Grinschgl, Sandra [Verfasser]. "Determinants and consequences of offloading working memory processes / Sandra Grinschgl". Tübingen : Universitätsbibliothek Tübingen, 2020. http://d-nb.info/1218073225/34.
Testo completo
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Tuladhar, Rohisha. "Renewal and Memory Approaches to Study Biological and Physiological Processes". Thesis, University of North Texas, 2019. https://digital.library.unt.edu/ark:/67531/metadc1505157/.
Testo completoAbstract (sommario):
In nature we find many instances of complex behavior for example the dynamics of stock markets, power grids, internet networks, highway traffic, social networks, heartbeat dynamics, neural dynamics, dynamics of living organisms, etc. The study of these complex systems involves the use of tools of non-linear dynamics and non-equilibrium statistical physics. This dissertation is devoted to understanding two different sources of complex behavior – non-poissonian renewal events also called crucial events and infinite memory of fractional Brownian motion. They both generate 1/f noise frequency spectrum. Thus, we studied examples of both processes and also their joint action. We also tried to establish the role of crucial events in biological and physiological processes like biophoton emission during the germination of seeds, the dynamics of heartbeat and neural dynamics. Using a statistical method of analyzing the time series of bio signals we were able to quantify the complexity associated with the underlying dynamics of these processes. Finally, we adopted a model that unifies both crucial events and memory fluctuations to study the rhythmic behavior observed in heart rate variability of people during meditation. We were able to also quantify the level of stress reduction during meditation. The work presented in this dissertation may help us understand the communication and transfer of information in complex systems.
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Lusena, Christopher. "Finite Memory Policies for Partially Observable Markov Decision Proesses". UKnowledge, 2001. http://uknowledge.uky.edu/gradschool_diss/323.
Testo completoAbstract (sommario):
This dissertation makes contributions to areas of research on planning with POMDPs: complexity theoretic results and heuristic techniques. The most important contributions are probably the complexity of approximating the optimal history-dependent finite-horizon policy for a POMDP, and the idea of heuristic search over the space of FFTs.
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Edwards, Lindsey C. "An investigation of cognitive processes in chronic pain". Thesis, University College London (University of London), 1992. http://discovery.ucl.ac.uk/1348982/.
Testo completoAbstract (sommario):
This thesis examines information-processing in chronic pain. "Schematic" processing is investigated selective memory for pain-related information is explored in depressed and non-depressed chronic pain patients, depressed non pain-patients and controls. A memory bias for sensory adjectives is found in the non depressed chronic pain group, while a tendency to over-recall both sensory and affective compared to neutral information is found in the depressed chronic pain group. No memory bias is observed in an acute pain group, and the implications of this are discussed. A possible cognitive avoidance mechanism is identified in depression. A questionnaire assessing beliefs about pain ("conceptual" processing) is developed and validated, and shown to differentiate between chronic pain patients and controls. The impact of two interventions for chronic pain (surgery and cognitive-behavioural management) on schematic and conceptual processing is investigated prospectively. In general the endorsement of organic beliefs decreases while the emphasis on psychological beliefs increases post-intervention. Evidence is found to suggest that surgery, but not cognitive-behavioural treatment, reverses pain-related memory biases. This is discussed in relation to changes in pain intensity. Evidence is provided to suggest that beliefs are causally related to several pain-related measures including anxiety, depression, health locus of control, cognitive coping strategies and activity levels. A word completion paradigm is employed to explore further the role of schematic processing in chronic pain, and finally, a lexical decision task is used to assess the role of word frequency effects in information-processing in chronic pain. These results suggest that memory biases in chronic pain cannot be explained by frequency effects, hence addressing the validity of the memory biases described earlier in the thesis.
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Ozyoruk, Nilufer. "A Computational Model Of Memory Processes In The Expectation-violation Effect". Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12605821/index.pdf.
Testo completoAbstract (sommario):
This thesis focuses on modeling Expectation-Violation Effect, which is the superior recall of weakly associated pairs of words over strongly associated pairs. The goal of this thesis is to provide an exploratory computational model. A virtual experiment is conducted based on the datasets used in the psychological experiment by Amster et al. (1992). The computational modeling of this phenomenon is carried in the medium of ACT-R cognitive architecture.
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Shumeyko, Yevgen [Verfasser]. "Data adaptive wavelet methods for Gaussian long-memory processes / Yevgen Shumeyko". Konstanz : Bibliothek der Universität Konstanz, 2012. http://d-nb.info/1023210363/34.
Testo completo