Thesis (Ph. D.)--Washington State University, December 2008. / Title from PDF title page (viewed on Sept. 23, 2008). "Department of Psychology." Includes bibliographical references (p. 48-56).

Thesis (PHD)--University of Montana, 2009. / Contents viewed on April 30, 2010. Title from author supplied metadata. Includes bibliographical references.

Previous research has shown that insufficient sleep at night and daytime sleepiness contributes to psychological distress, cognitive deficiencies and poor academic performance. The current study examines the effect of nighttime sleep extension on sleep, psychological health, academic performance and cognitive functioning in a sample of adolescents with complaints of daytime sleepiness and insufficient nighttime sleep.Participants were 56 adolescents (34 females) aged 14 - 18 (Mean age = 16.46). Participants were given daily sleep diaries and actiwatch during an initial interview. Sleepiness, psychological, academic and cognitive assessments were completed after one week of sleep data collection. The participants were randomly assigned to either extend their sleep for at least 60 minutes on three consecutive school nights or continue with their normal sleep schedule. After the sleep extension the same battery of tasks were completed. Baseline and post-intervention sleep, psychological, academic and cognitive data included daily sleep diaries, the Pediatric Daytime Sleepiness Scale (PDSS), State Trait Anxiety Scale - Short (STAI-S), AIMS reading comprehension and mathematic questions, digit span, verbal fluency, trail making and go/no go inhibition.Nineteen of those assigned to extend their sleep succeeded (M = 80.35 min.). Repeated measures ANOVAs were performed on sleep, psychological well being, academics and cognitive assessments to evaluate the sleep extension intervention. Interactions for the sleep variables found that Sleep Extenders decreased difficulty in waking in the morning and daytime sleepiness, increased time in bed, total sleep time and sleep efficiency more than Non-Sleep Extenders, (all p < .05). No differences were found for the STAI-S or the academic questions. All participants improved on the forward digit span (p < .05); however, t-tests showed that only the Sleep Extenders improved on the backward digit span (p < .05). All participants performed worse on the verbal fluency task, (p < .01). Everyone improved on trail making part A (p < .01), however, only Sleep Extenders improved on trail making part B, (p < .01).Even small increases in the duration of nighttime sleep can improve sleep variables, reduce daytime sleepiness, and produce improvement on measures of cognitive ability requiring mental control and flexibility in adolescents.

Sleep is well-established to become more superficial and fragmented as we age, with deficits in cognitive processing also commonly observed. While effects have been identified in both humans and mice (used in this thesis), there are important species differences in these findings and importantly, very little is known about the neural dynamics underlying these changes. By integrating several state-of-the-art approaches from putative single unit electrophysiological recordings to behavioural and pharmacological assessments, this thesis aimed to provide novel insights into the neural mechanisms involved in the age-dependent changes in sleep and cognition in mice. Firstly, this thesis investigated the neural activity underpinning the known global sleep changes that occur with ageing. Surprisingly, the majority of neuronal measures quantified in this study were resilient to the effects of ageing. Therefore the global sleep disruptions identified with ageing are unlikely to arise from changes in local cortical activity. Secondly, diazepam injection was found to suppress neural activity, in addition to previously reported effects on electroencephalography (EEG). Subtle differences in the effects of diazepam were identified across age groups, which may account for the variability seen in the efficacy of benzodiazepines in older individuals. Thirdly, ageing and sleep deprivation were found to have only a few effects on performance in a spatial learning task, the Morris water maze (MWM). Suggesting that spatial learning may be fairly resilient to the effects of ageing and sleep deprivation. Finally, this thesis presents preliminary analyses that showed mice were able to perform two novel paradigms of the visual discrimination task, suggesting their suitability in studying the link between ageing, sleep and cognition. Together the studies presented in this thesis provide insights into the differences between global and local mechanisms affected by ageing. Only by understanding local mechanisms will we be able improve on current treatments aimed at helping with the unwanted effects of healthy ageing, such as cognitive decline and sleep disruptions.