Browsing by Subject "working memory"
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Item Can an Unpredictable Childhood Environment Enhance Working Memory? Testing the Sensitized-Specialization Hypothesis(2017-05) Young, EthanAlthough growing up in an adverse childhood environment tends to impair cognitive functions, evolutionary-developmental theory suggests otherwise. In particular, a person’s mind may become developmentally specialized and potentially enhanced for solving problems in the types of environments in which the person grew up. In the current studies, we tested whether these specialized advantages in cognitive function might be sensitized to emerge in currently uncertain contexts. We refer to this as the sensitized-specialization hypothesis. We conducted experimental tests of this hypothesis in the domain of working memory, examining how growing up in unpredictable versus predictable environments affects different facets of working memory. Although growing up in an unpredictable environment typically impairs working memory, we show that this type of environment has positive effects on those aspects of working memory that are useful in rapidly changing environments. We also show that growing up in predictable environments enhances those aspects of working memory that are useful in stable environments. Both of these effects emerged only when the current context was uncertain. These theoretically-derived findings suggest that childhood environments shape, rather than uniformly impair, cognitive functions.Item Linking topiramate exposure to changes in electrophysiological activity and behavioral deficits through quantitative pharmacological modeling(2019-05) Callisto, SamuelTopiramate is a broad-spectrum anti-epileptic drug used to treat a variety of conditions, including epilepsy, migraine, substance abuse, mood, and eating disorders. We investigated the effects of topiramate on the working memory system using population pharmacokinetic-pharmacodynamic modeling and unsupervised machine learning approaches. Working memory is the capacity-limited neurocognitive system responsible for simultaneous maintenance and manipulation of information in order to achieve a goal. Behavioral and electrophysiological indices of working memory function were measured using data collected during a double-blind, placebo-controlled crossover study in healthy volunteers. Subjects completed a Sternberg working memory task, during which accuracy and reaction time were measured, while subjects’ EEG was recorded. A pharmacokinetic-pharmacodynamic model was constructed which demonstrated that accuracy decreased linearly as a function of plasma concentration, and that the magnitude of individual deficits was predicted by working memory capacity. A separate pharmacokinetic-pharmacodynamic model was developed which showed that spectral power in the theta frequency band (4-8 Hz) recorded during the retention phase of the Sternberg task increased as a function of plasma concentration. Furthermore, a mixture model identified two subpopulations with differential sensitivity in topiramate-induced theta reactivity. In the subpopulation defined by lower reactivity, reaction times were 20% slower than in the high theta reactivity subpopulation. Principal component regression was used to quantify the relationship between changes in multiple measures of electrophysiological activity and behavioral deficits. Theta power during retention was found to be the best predictor of topiramate-related behavioral deficits. Performance on another working memory task, Digit Span Forward, was also predicted by theta power during retention, as well as alpha (8-12 Hz) power during encoding and retrieval stages. In conclusion, two treatment-independent factors that predict differences in behavioral and electrophysiological responses to topiramate administration were identified: working memory capacity and theta reactivity. Future research will be needed to determine the utility of these demographic factors in predicting risk of cognitive side effects in patients eligible for treatment with topiramate.Item Neural Abnormalities Related to Visual Working Memory in People with Schizophrenia and their First-Degree Relatives(2016-07) Lynn, PeterProminent working memory (WM) deficits have been observed in people with schizophrenia (PSZ) across multiple sensory modalities, including the visuospatial realm. Observed deficits in electrophysiological correlates of early visual processing as well as later cognitive processes in PSZ are thought to underlie deficiencies in WM ability, though the mechanisms linking the two are not well understood. WM deficits and associated electrophysiological abnormalities have also been observed in unaffected relatives of PSZ (REL), suggesting WM dysfunction may be indicative of genetic liability for the disorder. We administered a delayed response visuospatial WM task to 23 PSZ, 30 of their REL, and 37 healthy controls (CTRL) in an effort to better understand the contributions of neural abnormalities to WM performance deficits associated with schizophrenia. PSZ performed more poorly on the WM task and gained less benefit from the presence of irrelevant stimuli than did CTRL and REL. In terms of electrophysiological responses, N1 responses to probes during retrieval differentiated the type and locations of stimuli presented during encoding in CTRL. Retrieval N1 responses in PSZ, however, failed to do so, while retrieval responses in REL showed more pronounced differentiation of stimulus features during encoding. Furthermore, neural responses during retrieval predicted behavioral performance in PSZ and REL, but not CTRL. These results suggest retrieval processes are particularly important to efficient visuospatial WM function in PSZ and REL, and support further investigation of WM retrieval as a potential target for improving overall WM function through clinical intervention.Item The Effects of Psychosocial Threat on Working Memory Performance in Anxious Individuals(2024-05-24) Anderson, Jillian CA large area of anxiety research assesses two key characteristics, state and trait anxiety. Scholars find that individuals with high trait anxiety have difficulty disengaging their attention away from threatening stimuli. When in a threatening situation, people may experience elevated heart rate, increased skin conductance, and ruminating thoughts. This can distract the individual during decision-making and further disturb their memory. Thus, the current experiment intended to examine specific variables that affect the relationship between stress and working memory performance in anxious and non-anxious individuals. Variables that were expected to influence working memory performance included levels of state and trait anxiety, and physiological arousal. Participants first completed a complex working memory task (OSPAN task) followed by undergoing a common psychosocial stressor (Trier Social Stress Test) and completed the OSPAN task again. Heart rate and skin conductance levels were also collected. Results showed that heart rate and skin conductance levels were significantly elevated during the Trier Social Stress Test compared to baseline measures. State anxiety also significantly increased from baseline to after the stress test. Furthermore, overall working memory performance was better on the second round of the working memory task. However, participants who experienced the greatest increases in state anxiety performed the worst on the second round. The current findings contribute to the growing body of literature on the individual’s cognitive and physiological responses as they experience anxiety and stress.Item Understanding Factors Contributing To Variability In Outcomes of Cochlear-Implant Users(2020-06) O'Neill, ErinCochlear implants (CIs) are a beneficial and often life-changing treatment for individuals with profound sensorineural hearing loss. However, despite advances in device design and surgical techniques, clinicians continue to see a very wide range of outcomes for individual CI users. Some CI users are able to converse successfully over the phone and in noisy environments, while others struggle to communicate effectively even in quiet, one-on-one conversations. Clinical differences between patients, such as the onset and duration of deafness, and anatomical factors related to the electrode-to-neuron interface, explain relatively little of this overall variability in speech perception. This dissertation addresses various perceptual, cognitive, and social factors, such as spectral resolution, working memory, intellectual efficiency, social engagement, and coping strategies, which may account for some of the individual differences in speech understanding found in the CI population. First, the amount of variability inherent to difficult auditory tasks was assessed by measuring the variance in the perception of degraded speech in the normal-hearing population. Associations between the perception of degraded speech, working memory, and intellectual efficiency were also explored in CI users and both young and age-matched normal-hearing controls. The listening strategy of “filling in the blanks” or leveraging context to understand words that are not heard or misheard was also explored by using novel sentences with and without semantic context. Finally, ecological momentary assessments were used to assess social and listening behavior of CI users outside of the lab setting, by having participants complete short surveys on their smartphones while engaging in normal daily activities. Results indicate that listening difficulty associated with degraded speech perception and working memory abilities account for some variance seen in outcomes of CI users. Strategies such as leveraging semantic context and using visual cues to supplement auditory information are also widely used in the CI population. Finally, greater levels of social engagement were associated with better speech perception outcomes in individual CI users. These new insights into cognitive and social factors influencing outcomes in CI users could be used by clinicians to tailor rehabilitation and manage expectations in individual patients.