• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 256
  • 128
  • 37
  • 35
  • 26
  • 2
  • Tagged with
  • 521
  • 301
  • 279
  • 236
  • 236
  • 140
  • 76
  • 68
  • 64
  • 62
  • 52
  • 52
  • 39
  • 36
  • 36
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Effects of Cannabis Dependence on Cognitive Function in Males with Schizophrenia

Rabin, Rachel Allison 19 December 2011 (has links)
Background: Cognitive impairment and cannabis use are common among patients with schizophrenia. However, the moderating role of cannabis on cognition remains unclear. Aim: We sought to examine cognition and symptomatology as a function of cannabis use patterns in schizophrenia. Methodology: Cognition was assessed in male outpatients with current cannabis dependence (n=18), historical cannabis dependence (n=21) and patients with no lifetime use (n=8). In addition, we explored the relationship between cumulative cannabis exposure and cognition among lifetime users. Results: Lifetime cannabis users demonstrated better processing speed than patients with no lifetime use. Notably, patients with current dependence exhibited robust relationships between cumulative cannabis exposure and cognition; associations were absent in former users. Conclusions: Cannabis status has minimal effects on cognition in schizophrenia. However, cumulative cannabis exposure significantly impairs cognition in current, but not former users, suggesting that the state dependent negative effects of cannabis may be reversed with sustained abstinence.
2

Effects of Cannabis Dependence on Cognitive Function in Males with Schizophrenia

Rabin, Rachel Allison 19 December 2011 (has links)
Background: Cognitive impairment and cannabis use are common among patients with schizophrenia. However, the moderating role of cannabis on cognition remains unclear. Aim: We sought to examine cognition and symptomatology as a function of cannabis use patterns in schizophrenia. Methodology: Cognition was assessed in male outpatients with current cannabis dependence (n=18), historical cannabis dependence (n=21) and patients with no lifetime use (n=8). In addition, we explored the relationship between cumulative cannabis exposure and cognition among lifetime users. Results: Lifetime cannabis users demonstrated better processing speed than patients with no lifetime use. Notably, patients with current dependence exhibited robust relationships between cumulative cannabis exposure and cognition; associations were absent in former users. Conclusions: Cannabis status has minimal effects on cognition in schizophrenia. However, cumulative cannabis exposure significantly impairs cognition in current, but not former users, suggesting that the state dependent negative effects of cannabis may be reversed with sustained abstinence.
3

Brain-music Duet: MEG Signal Complexity and Auditory Perception in Musicians and Nonmusicians

Carpentier, Sarah M. 20 December 2011 (has links)
Music training has been suggested to lead to an enhancement in the neural activity associated with music processing. It has been proposed that brain signal complexity is a reflection of the functional capacity of that neural system. The present study tested the hypothesis that musicians have a larger repertoire of brain activity associated with musical perception then nonmusicians. We used multiscale entropy to capture the complexity of the MEG signal while musicians and nonmusicians listened to different melodies. We observed that initial melody presentation elicited higher complexity in musicians compared to nonmusicians. Brain signal complexity decreased in both groups as a function of stimulus repetition. We propose that the neural networks that underlie auditory processing have a more diverse range of functioning in musicians, as compared to nonmusicians. Repetition reduces the amount of information processing and corresponding brain signal complexity.
4

Brain-music Duet: MEG Signal Complexity and Auditory Perception in Musicians and Nonmusicians

Carpentier, Sarah M. 20 December 2011 (has links)
Music training has been suggested to lead to an enhancement in the neural activity associated with music processing. It has been proposed that brain signal complexity is a reflection of the functional capacity of that neural system. The present study tested the hypothesis that musicians have a larger repertoire of brain activity associated with musical perception then nonmusicians. We used multiscale entropy to capture the complexity of the MEG signal while musicians and nonmusicians listened to different melodies. We observed that initial melody presentation elicited higher complexity in musicians compared to nonmusicians. Brain signal complexity decreased in both groups as a function of stimulus repetition. We propose that the neural networks that underlie auditory processing have a more diverse range of functioning in musicians, as compared to nonmusicians. Repetition reduces the amount of information processing and corresponding brain signal complexity.
5

Encoding Modulates the Interplay between Behavioural Priming and Recognition Processes

Guild, Emma Bennett 09 January 2014 (has links)
Recent research has demonstrated that priming and recognition memory performance are not independent as traditionally thought. Evidence is accumulating suggesting that information recognized in great detail (recollected) also has higher levels of priming (Sheldon & Moscovitch, 2010; Turk-Browne, Yi, & Chun, 2006). The purpose of this dissertation was to delineate the conditions under which recognition processes (estimates of recollection and familiarity) are associated with priming, and how this changes with age. Results from a systematic crossing of level of encoding (deep versus shallow) with type of priming task (conceptual versus perceptual) suggests that the relation between priming and recognition is determined by the nature of the encoding task. Under deep encoding conditions, a greater magnitude of priming—both perceptual and conceptual—was related to subsequent recollection but only amongst younger adults. Under shallow encoding conditions, perceptual priming performance was related to subsequent familiarity in both younger and older adults. Taken together, this series of experiments suggests that the processing mode engaged during encoding dictates which processes will be engaged at retrieval (a recollection-based process, or a familiarity-based process; Henke, 2010). These findings also suggest that both recollection and familiarity have rapid and unconscious aspects that are measurable through behavioural priming tasks, aligning with a recently proposed model suggesting recollection is characterized by a two-stage process, an early, relatively automatic and unconscious stage and a later, controlled and conscious stage (Moscovitch, 2008). It is suggested that the rapid, unconscious aspects of recollection may decline across the lifespan, while the rapid, unconscious aspects of familiarity stay intact with age.
6

Encoding Modulates the Interplay between Behavioural Priming and Recognition Processes

Guild, Emma Bennett 09 January 2014 (has links)
Recent research has demonstrated that priming and recognition memory performance are not independent as traditionally thought. Evidence is accumulating suggesting that information recognized in great detail (recollected) also has higher levels of priming (Sheldon & Moscovitch, 2010; Turk-Browne, Yi, & Chun, 2006). The purpose of this dissertation was to delineate the conditions under which recognition processes (estimates of recollection and familiarity) are associated with priming, and how this changes with age. Results from a systematic crossing of level of encoding (deep versus shallow) with type of priming task (conceptual versus perceptual) suggests that the relation between priming and recognition is determined by the nature of the encoding task. Under deep encoding conditions, a greater magnitude of priming—both perceptual and conceptual—was related to subsequent recollection but only amongst younger adults. Under shallow encoding conditions, perceptual priming performance was related to subsequent familiarity in both younger and older adults. Taken together, this series of experiments suggests that the processing mode engaged during encoding dictates which processes will be engaged at retrieval (a recollection-based process, or a familiarity-based process; Henke, 2010). These findings also suggest that both recollection and familiarity have rapid and unconscious aspects that are measurable through behavioural priming tasks, aligning with a recently proposed model suggesting recollection is characterized by a two-stage process, an early, relatively automatic and unconscious stage and a later, controlled and conscious stage (Moscovitch, 2008). It is suggested that the rapid, unconscious aspects of recollection may decline across the lifespan, while the rapid, unconscious aspects of familiarity stay intact with age.
7

Implicit and Explicit Consequences of Distraction for Aging and Memory

Thomas, Ruthann C. 15 September 2011 (has links)
This investigation explored implicit and explicit memory consequences of age differences in susceptibility to distraction when previous distraction occurs as target information in a later memory task. Younger and older adults were presented with either implicit (Study 1) or explicit (Studies 2 and 3) memory tasks that included previously distracting and new words. Study 1 explored whether prior exposure to distraction would transfer to improve memory when previously distracting words were included in list to be studied for a recall task. Older adults recalled more previously distracting than new words whereas younger adults recalled the same amount of previously distracting and new words. This initial study was implicit in its use of previously distracting information in that participants were neither informed nor aware of their prior exposure to words in the recall task. Here, only older adults’ memory was influenced by prior exposure to distraction and their recall actually increased to the level of younger adults with implicit use of distraction to improve performance. Subsequent studies investigated explicit influences of prior exposure to distraction on later memory. In Study 2, both younger and older adults showed reliable memory for previously distracting words in an explicit recognition task. These results suggest that although younger adults encode distraction, they do not transfer this information when previous distraction occurs as target stimuli in an implicit memory task. Study 3 investigated whether participants would transfer previous distraction to improve recall if the task was explicit in its use of previous distraction. When cueing instructions were given before the memory task informing participants of the connection between tasks, older adults once again recalled more previously distracting than new words. In contrast to the results of Study 1, younger adults also recalled more previously distracting than new words. Taken together, the results indicate that younger adults do encode distraction, but they require explicit instructions to transfer their knowledge of distraction to later tasks. In contrast, older adults apply their knowledge of distraction in both implicit and explicit memory tasks. Implications are discussed in terms of inhibitory control theory and age differences in strategies engaged in memory tasks.
8

Beyond Episodic Memory: Medial Temporal Lobe Contributions to Problem-solving and Semantic Fluency Tasks

Sheldon, Signy Anne Marie 31 August 2011 (has links)
The purpose of this thesis was to examine the contribution of episodic memory processes supported by the medial temporal lobes (MTL) to two goal-oriented non-episodic tasks, problem solving and semantic retrieval (verbal fluency). The reported experiments provide evidence for the hypothesis that MTL-based episodic processes are robustly involved in completing non-episodic tasks that are open-ended in that no algorithm or procedure can be applied to obtain task-relevant information. In Experiments 1 and 2, participants were administered the Means-End-Problem-Solving (MEPS) task, an open-ended test of social problem solving. People with impaired episodic memory associated with MTL damage or deterioration, patients with temporal lobe epilepsy or excisions (TLE) and older adults, performed worse than matched controls at solving such problems. Importantly, the participants’ performance on the MEPS as judged by the number of relevant solution steps generated correlated with the number of internal (episodically-relevant) but not external (semantically-relevant) details provided in the solutions. Thus, information derived from episodic memory benefited performance on the MEPS. Experiments 3 and 4 were conducted to ascertain whether open-endedness and episodic relevance are determinants of MTL contributions to performance on tests of verbal fluency, which traditionally are considered the domain of semantic memory. Using fMRI, Experiment 3 tracked the time course of MTL activation as participants performed a fluency task for categories that ranged in episodic relevance. The MTLs were more active throughout for categories that depended on autobiographical memories, not active for categories that were not episodically relevant, and active for episodic/spatial categories only later in the time course as the task moved from being well-defined to open-ended. The necessary involvement of the MTL in these tasks was confirmed by the pattern of spared and impaired performance of patients with TLE on category fluency tasks (Experiment 4). Together, these findings are consistent with the view that MTL-based processes are involved in tasks beyond those that test episodic memory. Furthermore, these studies suggest that performance on non-episodic tasks recruits the MTL most robustly when a task is open-ended.
9

Happy Distraction: Positive Affect Broadens Attention to Irrelevant Information

Biss, Renee Katherine 24 February 2009 (has links)
The present study investigated the claim that positive mood broadens the scope of attention to include irrelevant information, and if so, whether this loosening of attentional control has longer term cognitive consequences. In Experiment 1, participants in an induced happy mood were more influenced by distracting information that interfered with responses in the global-local task, particularly when this information was global in nature. Experiment 2 demonstrated that, when previously irrelevant information became solutions on a subsequent task, implicit memory for this distraction was positively correlated with naturally-occurring positive mood. This study corroborates findings that individuals in a happy mood are more affected by distracting irrelevant information. Furthermore, this widened scope of attention can facilitate performance on a subsequent task, a finding with implications for the relationship between positive mood and creativity.
10

Effects of Attention on Change Deafness

Backer, Kristina Carol 14 December 2010 (has links)
Detecting acoustic changes in our environment, such as a rattlesnake’s sudden approach, can be essential for survival. Although auditory change detection has been intensively investigated using sequentially-presented sounds, very little is known about how we detect changes in a natural, complex scene comprised of multiple concurrent sounds. The present study used a location-switch change deafness paradigm; on each trial, participants listened to two consecutive auditory scenes, consisting of three natural sounds played in distinct locations, and reported if the two scenes were the same or identified the two sounds that switched locations. Directing a listener’s attention to a changing sound improved accuracy and decreased reaction time, relative to uncued trials. However, when participants’ attention was invalidly directed to a non-changing sound object, performance suffered. Further analyses showed that these effects could not be explained by energetic masking. Thus, attention is necessary for change identification in complex auditory scenes.

Page generated in 0.0236 seconds