Theses and Dissertations at Montana State University (MSU)
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Item The effects of working memory capacity on collaborative inhibition across categorized and unrelated lists(Montana State University - Bozeman, College of Letters & Science, 2024) De Silva, Siyambalapitige Ninoo Nethmalie; Chairperson, Graduate Committee: Michelle L. MeadeThe current study examined if working memory capacity (WMC) predicts collaborative inhibition and if this influence can be generalized across categorized and uncategorized lists. Across two experiments, participants' WMC was measured using the operation span, reading span, and symmetry span. They were then presented with the unrelated lists only (Experiment 1), or unrelated words lists and categorized word lists (Experiment 2). Participants were asked to recall the lists on their own or in collaboration with another participant (recall test 1). In addition, they were given a subsequent individual recall test (recall test 2), and an individual source monitoring recognition test. Results from both experiments showed collaborative inhibition in recall test 1 and post collaborative benefits in recall test 2. Importantly, the pattern of collaboration results did not vary across WMC. Higher WMC individuals and lower WMC individuals showed similar effects of collaboration across unrelated and categorized lists. These findings identify important parameters of if and when WMC influences collaborative memory. Moreover, future research can investigate if mechanisms such as attentional control, retrieval inhibition, and collaborative process variables related to collaborative inhibition play a role when WMC is at work.Item Pupil response as a measure of preparatory control of attention in anticipation of deception(Montana State University - Bozeman, College of Letters & Science, 2024) Brennan, Evan Michael; Chairperson, Graduate Committee: Keith A. HutchisonDeception is generally considered to be more cognitively demanding than telling the truth, driving research interest in the relationship between deception and cognitive ability. Few studies have explored the preparatory attentional state occurring after the decision to be dishonest is made, but before the content of the question is known to the deceiver. Participants in the current study were given "Truth" or "Lie" prompts several seconds before being asked questions about autobiographical information that they answered according to the prompt. Cue-evoked pupillary responses, or the changes in participants' pupils during the fixation period between the prompt and question presentation, served as an objective physiological measure of this preparatory state of attention. To assess cognitive ability, several tasks assessing working memory capacity and attentional control were also administered to determine their relationship with pupil response. Aligned with results from a former study, it was hypothesized that pupil diameter would be greatest in anticipation of "Lie" trials, that working memory capacity and attentional control would be negatively correlated with the proportion of errors committed and positively correlated with pupil size in the final few seconds of the fixation interval, and that pupil diameter variability across the fixation interval would be positively correlated with the proportion of errors committed. Results showed a general pattern of constriction in pupil diameter in the fixation interval, which opposed results from previous studies, and did not provide support for the main hypotheses. Lie trials where participants committed an error displayed a significant decrease in pupil diameter across the fixation interval relative to accurate lie trials. Possible reasons for general pattern of pupil constriction are given, prompting a retesting of the hypotheses under better experimental conditions. It is still possible that there is a general pattern of pupil dilation in this preparatory period.Item Testing the effectiveness of heart rate variability biofeedback as a method to improve attention control(Montana State University - Bozeman, College of Letters & Science, 2023) Hood, Audrey Victoria Blackwell; Chairperson, Graduate Committee: Keith A. HutchisonThe current dissertation sought to 1) examine the relationship between working memory capacity (WMC), attention control, and high-frequency heart rate variability (HF-HRV) and 2), to implement an HRV biofeedback training with the goal of increasing resting baseline HF-HRV, and in turn, attention control task performance. In both experiments, physiological measurements were collected during a seated, resting baseline using electrocardiograph electrodes and BioNomadix receivers which transmitted signals to a BioPac MP-150/160 System. The HRV index used in this study was calculated from the inter-beat intervals and inter-breath intervals data extracted from the electrocardiograph and respiration signals. In Experiment 1, participants first underwent a resting baseline period to assess their HRV and then completed two WMC tasks. Experiment 2 took place during two laboratory sessions with a week-long at-home training between lab Sessions 1 and 2. At Session 1, participants first underwent a resting baseline period to assess their HRV and then completed two measures of WMC. They then completed three attention control tasks pre- and post-training. For the training, those randomly assigned to the HRV biofeedback condition underwent a breathing exercise, whereas those randomly assigned to the active control condition completed wordsearch puzzles. Participants were asked to practice the breathing/wordsearch exercises at home for one week. At Session 2, participants underwent a resting baseline physiological assessment followed by the three attention control tasks again. Results demonstrated that HF-HRV is weakly correlated with WMC and attention control and that brief, 5-minute sessions of HRV biofeedback are not sufficient to increase levels resting baseline HF-HRV.Item Delay in short term memory as a result of extended periods of rehearsal prevention(Montana State University - Bozeman, College of Letters & Science, 1976) Bashor, Gregory LeeItem The Fronto-Parietal network and beyond : a study of the spatiotemporal patterns underlying visual working memory(Montana State University - Bozeman, College of Letters & Science, 2014) Dotson, Nicholas Monroe; Chairperson, Graduate Committee: Charles M. Gray; Rodrigo F. Salazar and Charles M. Gray were co-authors of the article, 'Spatiotemporal activity patterns reveal the interplay between integration and segregation during visual working memory' which is contained within this thesis.Working memory, an integral component of higher cognitive functions, involves the short-term retention and utilization of behaviorally relevant information when that information is no longer available in the environment. Tragically, individuals suffering from traumatic brain injuries, psychiatric disorders, and other neurological disorders often exhibit working memory deficits. The study of working memory may thus provide insight into the mechanisms underlying cognitive functions and the potential to alleviate major health problems. In order to understand cognitive processes, like working memory, several pieces of information must be considered: the cortical and sub-cortical areas involved, the manner in which these areas integrate, or share information, and the underlying dynamics of these integrative processes. These pieces form a hierarchical structure of investigation, from the individual areas to global principles of coordination. The objective of this study is to elucidate the relevant spatiotemporal patterns of oscillatory synchronization underlying visual working memory in the fronto-parietal network and across the brain. Relevant patterns for consideration are those that encode stimulus information, are modulated by the task, and those with distinct anatomical variations. The results of the studies presented in Chapters 2-4 provide extensive evidence that oscillatory synchronization is a mechanism for distributed integration. We show that the patterns of coherent activity 1) encode working memory items, 2) are indicative of the task period, 3) provide the potential for multiple functional networks, defined by the relative phase and, 4) are highly dynamic, with large fluctuations in magnitude and relative phase. Future studies will be necessary to further investigate the role of oscillatory synchronization. Efforts to perturb oscillatory activity in order to illustrate its utility, rather than simply correlating its activity with stimulus and task components, will be crucial. Finally, understanding the spatiotemporal activity patterns underlying working memory may ultimately allow for the identification of aberrant patterns, such as those brought on by disease, and allow for these patterns to be meaningfully interacted with - via neuroprosthetic devices.