Browsing by Subject "Sustained attention"
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Item Associations between sleep and memory in aging(2016-05) Sherman, Stephanie Michelle; Schnyer, David M.; Beevers, Christopher G; Haley, Andreana P; Westerberg, Carmen EThe goal of this dissertation was to understand how changes in sleep influence memory performance in healthy older adults. Previous research suggests that older individuals experience parallel declines in sleep and episodic memory. These age-related changes appear to be linked such that sleep disruptions contribute to deficits in memory performance. We examined the components of episodic memory that changed following sleep loss and correlated with aspects of sleep physiology. Healthy older adults completed two overnight sessions: an in-lab sleep recording session and a 24-hour sleep deprivation session. The morning after each sleep manipulation, participants completed both episodic memory and sustained attention tasks. We applied computational models, specifically drift-diffusion models, to the episodic memory tasks to examine whether sleep loss affected memory indirectly through lapses in sustained attention (vigilance hypothesis) or specifically through declines in the strategic processes associated with memory (neuropsychological hypothesis). Our results showed that memory functions that depend on processes associated with the prefrontal cortex were impaired following sleep deprivation. In addition, sleep loss caused a small but robust impairment in sustained attention. Since multiple cognitive processes were impaired by sleep loss in older adults, these findings do not provide unequivocal support for either the neuropsychological hypothesis or the vigilance hypothesis. In addition, we explored which aspects of sleep physiology (recorded during the sleep session) optimized components of memory performance. Our results illustrated that more slow wave power during sleep was correlated with higher next-day source memory strength. Additionally, individuals who spent more time in slow wave sleep had better memory retention. These results support further efforts to investigate sleep as a general indicator of cognitive function across the lifespan and highlight the importance of reinforcing healthy sleep behaviors as a method to preserve cognitive functioning in older adults.Item Computational analysis of meditation(2011-08) Saggar, Manish; Miikkulainen, Risto; Saron, Clifford D.; Schnyer, David M.; Ballard, Dana H.; Ravikumar, PradeepMeditation training has been shown to improve attention and emotion regulation. However, the mechanisms responsible for these effects are largely unknown. In order to make further progress, a rigorous interdisciplinary approach that combines both empirical and theoretical experiments is required. This dissertation uses such an approach to analyze electroencephalogram (EEG) data collected during two three-month long intensive meditation retreats in four steps. First, novel tools were developed for preprocessing the EEG data. These tools helped remove ocular artifacts, muscular artifacts, and interference from power lines in a semi-automatic fashion. Second, in order to identify the cortical correlates of meditation, longitudinal changes in the cortical activity were measured using spectral analysis. Three main longitudinal changes were observed in the retreat participants: (1) reduced individual alpha frequency after training, similar reduction has been consistently found in experienced meditators; (2) reduced alpha-band power in the midline frontal region, which correlated with improved vigilance performance; and (3) reduced beta-band power in the parietal-occipital regions, which correlated with daily time spent in meditation and enhanced self-reported psychological well-being. Third, a formal computational model was developed to provide a concrete and testable theory about the underlying mechanisms. Four theoretical experiments were run, which showed, (1) reduced intrathalamic gain after training, suggesting enhanced alertness; (2) increased cortico-thalamic delay, which strongly correlated with the reduction in individual alpha frequency (found during spectral analysis); (3) reduction in intrathalamic gain provided increased stability to the brain; and (4) anterior-posterior division in the modeled reticular nucleus of the thalamus (TRN) layer and increased connectivity in the posterior region of TRN after training. Fourth, correlation analysis was performed to ground the changes in cortical activity and model parameters into changes in behavior and self-reported psychological functions. Through these four steps, a concrete theory of the mechanisms underlying focused-attention meditation was constructed. This theory provides both mechanistic and teleological reasoning behind the changes observed during meditation training. The theory further leads to several predictions, including the possibility that customized meditation techniques can be used to treat patients suffering from neurodevelopmental disorders and epilepsy. Lastly, the dissertation attempts to link the theory to the long-held views that meditation improves awareness, attention, stability, and psychological well-being.Item Mothers’ depressive symptoms in infancy and children’s maladjustment in early grade school : the role of children’s sustained attention and executive function(2015-05) Wang, Yiji, Ph. D.; Dix, Theodore H.; Anderson, Edward; Bigler, Rebecca; Gershoff, Elizabeth T; Hazen-Swann, NancyUsing longitudinal data from the NICHD Study of Early Child Care and Youth Development (N=1,367), the current study examined the role of children’s sustained attention and executive function in promoting their adjustment difficulties in early grade school as mothers’ depressive symptoms increase in infancy. Findings demonstrated that, when mothers’ depressive symptoms were high in infancy, their children were at risk for poor sustained attention and executive function prior to school entry partly due to mothers’ tendencies to become insensitive. Children’s poor executive function in turn mediated the relation of mothers’ depressive symptoms in infancy to children’s poor cognitive and socioemotional adjustment in 3rd grade, independent of poor sustained attention. Findings also suggested the unique role of mothers’ depressive symptoms in infancy in predicting children’s poor sustained attention, but not executive function. Overall, this study demonstrates the potential role of children’s sustained attention and executive function in understanding the developmental risks children of depressed mothers face in early grade school.