Browsing by Subject "Memory, Short-Term"
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Item Cross-Sectional Differences in Brain Activity Supporting Working Memory(2011-12-12) Dewey, Laura Marie; Motes, Michael A.Cross-sectional developmental studies have shown working memory (WM) to follow monotonic developmental trajectories through childhood into adolescence. In contrast, structural neuroimaging studies have shown that several brain regions, such as the prefrontal cortex (PFC), follow nonlinear developmental trajectories from birth through late adulthood. The present study sought to explore the relationship between functional activation in brain regions supporting WM and age throughout adolescence. Forty-two healthy adolescents (aged 11 to 18) completed a delayed-response WM task while functional magnetic resonance imaging (fMRI) data were collected. Participants studied either one or six letters (3.5 seconds), remembered the items over a delay (5 seconds), and then judged whether a single probe letter was in the studied set (within 2.5 seconds). An fMRI blocked design was used: four blocks per set-size and three trials per block. Additionally, the participants completed the Digit Span subtest from the Wechsler intelligence tests in order to obtain behavioral measures of WM. Hierarchical regression analyses were used to evaluate linear and quadratic relationships between WM task-related signal-change per voxel and age while evaluating the potential mediating effects of WM indices (response time [RT], digit span forward, digit span backward). Linear relationships were found in right medial Brodmann’s Area (BA) 6, right cerebellum, and left BA34 when the linear effects of gender, handedness, response time, digit span forward, and digit span backward were controlled for statistically. Thus, activation increased with age within these regions, but the linear trends were being suppressed by the covariates. Activation on the WM task increased with age in right medial BA6 when the effects of WM indices, as measured in the present study, were removed. The separate relationship between WM capacity and right medial BA6 activation suppressed the detection of the relationship between right medial BA6 activation and age. The data support developmental, possibly maturational, changes in the role of medial PFC in WM that are independent of WM ability measures used in the present study. This finding has implications for broad theories about the development of WM and other cognitive abilities that allow for the identification of both normal and deviant developmental trajectories.Item The Relationship Between Two Endophenotypes of Psychosis in Volunteers with Schizophrenia and Bipolar Disorder(2010-11-02) Moates, Amanda Frances; Tamminga, CarolBackground: Deficits in smooth pursuit eye movements are an established endophenotype for schizophrenia (SZ) and are being investigated as a potential biomarker for psychotic bipolar disorder (BDP). While the molecular determinant of the physiological deficit is still unclear, considerable research has shown deficits in the predictive mechanism of eye movements in SZ using target-masking techniques, as well as with a more recent novel prediction eye movement task. The questions of whether this deficit is related to working memory alterations in SZ and extends to other psychotic disorders like BDP were a focus of this investigation. Methods: Volunteers with schizophrenia (SZ, n = 38), bipolar I disorder with psychotic features (BDP, n = 31), and healthy controls (HC, n = 17) performed a novel eye movement task to assess the predictive mechanism of smooth pursuit. Subjects also completed a battery of neuropsychological tasks that included measures of working memory. Results: Individuals with SZ and BDP performed similarly on both neuropsychological and eye tracking tasks. Both groups evidenced reduced predictive pursuit velocity and worse performance on the Wechsler Spatial Span task compared with healthy controls. Further, a small but significant correlation (r = .27, p = .03) between predictive pursuit gain and working memory performance on Spatial Span was obtained, without statistically significant correlations in other cognitive domains. Conclusions: Individuals with SZ and BDP showed similar deficits on the predictive pursuit eye movement task, suggesting that this alteration could be a characteristic of the psychosis domain. The a priori prediction that the predictive pursuit task is associated with working memory mechanisms was supported in part by its significant and selective correlation with a measure of working memory.Item [UT Southwestern Medical Center News](2009-01-25) Ladson, LaKishaItem Working Memory Differences in Pediatric Moderate and Severe Traumatic Brain Injury(2010-01-12) Fitzpatrick, Stephanie Ann; Stavinoha, Peter L.Traumatic brain injury is one of the leading causes of disability and impairment in children and adolescents. This study sought to determine the effects of severity on verbal working memory and verbal short-term memory. It was hypothesized that increased severity of injury would be associated with decreased performance on working memory tasks. Participants, aged 6-16 years, were tested 6 to 12 months after injury. The sample was comprised of 12 children and adolescents who had sustained a severe TBI and 11 children and adolescents who had sustained a moderate TBI. Results indicated that there were no significant differences between the moderately injured group and subjects with severe injuries on tasks of verbal working memory or verbal short-term memory. However, inspection of the data indicated that children in the severe group performed in the Low Average range, while children in the moderate group performed in the Average range. Results may be limited by the small sample size.