Chronic exposure to psychostimulants such as amphetamine (AMPH) can induce long-term disruptions in cognition via actions on prefrontal cortex dopamine. Previous work has shown that two types of executive functions, set shifting and working memory (WM), are disrupted by AMPH sensitization and that these cognitive domains are impaired in schizophrenics and stimulant abusers. We assessed the effects of AMPH sensitization on behavioural flexibility using a cross-maze set shifting task and a WM task using the delayed spatial win-shift (SWSh) task in Long Evans (LE) and Sprague Dawley (SD) rats. Rats were exposed to an AMPH sensitization regimen (15 AMPH or saline injections: 1-5 mg/kg every 2nd day, increasing the dose by 1 mg every 3rd injections) following habituation on the mazes. In experiment 1, LE and SD rats were initially trained on a visual cue discrimination. During the set shift, rats were required to shift from the previously acquired visual-cue-based strategy to a response strategy (e.g.; always turn left, ignore the visual cue). For the reversal, rats were trained to reverse their turn direction. AMPH treatment did not impair learning of the initial cue discrimination in either strain. However, AMPH treated rats learned the response discrimination faster than controls during the set shift and AMPH treated LE rats were faster than controls to reach acquisition criterion during the response reversal. AMPH treatment neither impaired nor improved reversal learning in SD rats. In experiment 2, rats were tested on the SWSh task in which spatial information acquired during a training phase was used 30 minutes later during the testing phase in order to retrieve food pellets on the maze. In this task, AMPH treated rats were faster to re-attain criterion than control rats. Correlational analysis further revealed that AMPH sensitized rats that required more days to reach criterion before AMPH treatment (i.e. slow learners) tended to make more errors during re-acquisition of the memory task. Viewed collectively, these results suggest that chronic AMPH treatment can enhance behavioural flexibility and WM assessed in this manner. However, repeated AMPH exposure may have exacerbated pre-existing cognitive deficits in slow learning rats. / Medicine, Faculty of / Graduate

Inattentive behavior is considered a core and pervasive feature of ADHD; however, an alternative model challenges this premise and hypothesizes a functional relationship between working memory and inattentive behavior. The current study investigated whether inattentive behavior in children with ADHD is functionally related to domain-general central executive and/or subsidiary storage/rehearsal components of working memory. Objective observations of children's attentive behavior by independent observers were conducted while children with ADHD (n=15) and typically developing children (n=14) completed 10 counterbalanced tasks that differentially manipulated central executive, phonological storage/rehearsal, and visuospatial storage/rehearsal demands. Results of latent variable and effect size confidence interval analyses revealed two conditions that completely accounted for the attentive behavior deficits in children with ADHD: (a) placing demands on central executive processing, the effe

No description available.

No description available.

<p dir="ltr">Spatial navigation is a complex skill that relies on many aspects of cognition. The following</p><p dir="ltr">studies aimed to clarify the role of working memory in spatial navigation, and particularly, the</p><p dir="ltr">potentially differential contributions of verbal and visuospatial working memory. Study 1</p><p dir="ltr">leveraged individual differences to understand how working memory differs among types of</p><p dir="ltr">navigators and the predictiveness of verbal and visuospatial working memory. Participants</p><p dir="ltr">completed multiple measures of verbal and visuospatial working memory and spatial navigation.</p><p dir="ltr">Study 2 further evaluated the impact of a working memory load on spatial navigation performance.</p><p dir="ltr">Using a dual-task paradigm, the decrement (or not) of performance on spatial navigation can be</p><p dir="ltr">compared between control, verbal, and visuospatial conditions. Study 1 showed that individual</p><p dir="ltr">differences in visuospatial working memory are more predictive than verbal working memory.</p><p dir="ltr">However, Study 2 provides evidence for the necessary role for both verbal and visuospatial</p><p dir="ltr">working memory.</p>

No description available.

Elaborated Intrusion (EI) Theory posits that craving involves mental imagery in the same sensory modalities as the craved substance or activity. Visual imagery predominates, therefore craving should selectively interfere with performance on visual task, and conversely visual tasks should interfere with craving. This thesis reports tests of this prediction, both in the laboratory and real-world settings, to provide a basis for designing practical tasks for interfering with cravings in a natural environment. Contrary to predictions, experiments 1 and 2 showed no effect of craving on visual or verbal task performance. There were, however, effects of task performance on craving in experiment 2. Experiment 3 found that playing Tetris reduced craving relative to a no-task control (watching a load screen), but was no more effective than digit recall or counting in ones. Experiments 4 and 5 both compared the effects of visual pattern recall with digit recall, with contradictory results. Experiment 4 showed an effect of low load visual task on craving, but not verbal; whereas Experiment 5 found no impact of either task. Overall, the findings are consistent with the assumption that craving involves controlled cognitive processes, but do not clearly support or disprove the hypothesis that visual processes are key. Experiment 6 focussed on interfering with naturally occurring cravings in a laboratory setting. Playing the computer game Tetris reduced cravings compared to a no task control. The final study of this thesis examined cravings in a natural environment. Participants were lent an iPod with either a questionnaire-only task, or a task with the questionnaire and Tetris installed on it. They were prompted by SMS to complete the task at pseudo-random intervals across the day over the course of a week. Mixed effects regression and multilevel growth curve modelling showed that Tetris was effective at decreasing naturally occurring cravings in a natural environment but the binary measure used, did not find a reduction in indulgence rates, however other more sensitive measures may. In contrast to the literature reviewed, the findings from this thesis are more consistent with craving involving general cognitive effort rather than modality-specific processes. Games such as Tetris appear to have potential as take-home tasks in future research and to help people manage their cravings.

Language processing is a complex task requiring the integration of many different streams of information. Theorists have considered that working memory plays an important role in language processing and that a reduction in available working memory resources will reduce the efficacy of the system. In debate, however, is whether or not there exists a single pool of resources from which all language processes draw, or if the resource pool is functionally fractionated into modular subsections (e.g. syntactic processing, lexical processing etc.). This thesis seeks to investigate the role that working memory capacity plays in the utilisation of context to facilitate language processing. We experimentally manipulated the resources available to each participant using a titrated extrinsic memory load (a string of digits the length of which was tailored to each participant). Participants had to maintain the digits in memory while reading target sentences. Using this methodology we conducted six eyetracking experiments to investigate how a reduction of working memory resources influences the use of context in different language processes. Two experiments examined the resolution of syntactic ambiguities (reduced relative clauses); three examined the resolution of lexical ambiguities (balanced homonyms such as appendix); and one explored semantic predictability (It was a windy day so the boy went to the park to fly his… kite). General conclusions are hard to draw in the face of variable findings. All three experiment areas (syntactic, lexical, and semantic) show that memory loads interact with context, but there is little consistency as to where and how this occurs. In the syntactic experiments we see hints towards a general degradation in context use (supporting Single Resource Theories) whereas in the Lexical and Semantic experiments we see mixed support leaning in the direction of Multiple Resource Theories. Additionally, while individual experiments suggest that limiting working memory resources reduces the role that context plays in guiding both syntactic and lexical ambiguity resolution, more sophisticated statistical investigation indicates that these findings are not reliable. Taken together, the findings of all the experiments lead us to tentatively conclude that imposing limitations on working memory resources can influence the use of context in some language processes, but also that that influence is variant, subtle, and hard to statistically detect.

Computerized cognitive training is recognized as an appropriate tool in enhancing working memory in individuals with and without physical limitations. Previous researchers have examined the application of computerized cognitive training in stroke patients, children suffering from ADHD, and older adults. Presently, there is a lack of controlled studies regarding computerized cognitive training in low-achieving primary school students. The goal of this study was to examine the interactions among working memory, computerized cognitive training and academic achievement. Specifically, the study sought to determine whether low-achieving primary school students would significantly improve their mathematics achievement (as measured by the Grade Four Literacy Test) and working memory capacity (as measured by the Automated Working Memory Assessment) through computerized cognitive training on working memory. A random pre-test post-test control-group experimental study was conducted to test the research hypotheses. The experimental group received progressive computerized working memory training. The control group received basic computerized working memory training. Training for both groups of student was conducted the same time each day by the class teacher at the participants' school. The duration for practice was one hour per day, five days per week for five weeks. The working memory capacity of the experimental group was compared to the control group. Both experimental and control groups subjects showed improvements in working memory scores from the baseline pre-test to the post-test. Analysis of the multivariate tests suggests that there was significant difference (Wilks Lambda F = 2.880, p = .045) between the group receiving progressive computerized working memory training compared to the group receiving basic computerized working memory training. The mathematics achievement of the experimental group was compared to the control group immediately after completing training. Both the experimental and control group students showed improvement in post training mathematics scores. However, the difference between control and experimental group improvement was not significant (F = 2.719, p = .085). The end-of-term mathematics (six weeks after completing training) scores of the experimental group was compared to the control group. Both the experimental and control group students showed improvement in their end-of-term mathematics scores. However, the difference between control and experimental group improvement was not significant (F = 2.719, p = .085).

Older adults constitute a growing population in the United States. A disproportionate percentage of this population experience chronic illnesses and need to recall information important to prevent complications of illness and to self-manage their condition. One example of the need to retain information is to recall the risk factors for ischemic stroke to prevent the damaging effects of stroke.Factors that could influence the recall of health information include age-related changes in cognition, specifically working memory capacity. Research supports that older adults have working memory capacity limitations. Older adults may also experience low health literacy that in combination with declines in working memory could further influence recall of health information.The purpose of this study was to describe the predictive relationships of working memory capacity and health literacy on the recall of the warning signs of stroke in a sample of older community dwelling elders.Fifty-six participants, ranging in age from 68-99 years of age (M= 80 years of age) were recruited from two sites, a Senior Center and Retirement Residence. A brochure published by the American Heart and Stroke Association, "Let's Talk About Stroke" was the tool used to deliver the health information regarding the five warning signs of stroke. Personal factors including demographic and medical variables were collected in this study. Working Memory was assessed using the Wechsler Adult Intelligence Scale III, Working Memory Index (WMI). Health literacy was determined using the Short Test of Functional Health Literacy in Adults (STOFHLA). Participants were asked to recall the health information they were asked to read regarding the five warning signs of stroke at the conclusion of the study visit.Findings indicated that the key variables working memory and health literacy were independently and positively correlated to recall (p < .01); however, regression analysis did not demonstrate an interaction between the two key variables and recall.The findings from this study explore the associations between working memory, health literacy and personal factors and support that these key predictors may be related to the older adults ability to successfully recall health information.