Matching Items (9)
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- All Subjects: Cognitive Psychology
- All Subjects: Capacity
- Genre: Masters Thesis
- Creators: Brewer, Gene
- Resource Type: Text
- Status: Published
Description
As the number of devices with wireless capabilities and the proximity of these devices to each other increases, better ways to handle the interference they cause need to be explored. Also important is for these devices to keep up with the demand for data rates while not compromising on industry established expectations of power consumption and mobility. Current methods of distributing the spectrum among all participants are expected to not cope with the demand in a very near future. In this thesis, the effect of employing sophisticated multiple-input, multiple-output (MIMO) systems in this regard is explored. The efficacy of systems which can make intelligent decisions on the transmission mode usage and power allocation to these modes becomes relevant in the current scenario, where the need for performance far exceeds the cost expendable on hardware. The effect of adding multiple antennas at either ends will be examined, the capacity of such systems and of networks comprised of many such participants will be evaluated. Methods of simulating said networks, and ways to achieve better performance by making intelligent transmission decisions will be proposed. Finally, a way of access control closer to the physical layer (a 'statistical MAC') and a possible metric to be used for such a MAC is suggested.
ContributorsThontadarya, Niranjan (Author) / Bliss, Daniel W (Thesis advisor) / Berisha, Visar (Committee member) / Ying, Lei (Committee member) / Arizona State University (Publisher)
Created2014
Description
Self-control has been shown to predict both health risk and health protective outcomes. Although top-down or “good” self-control is typically examined as a unidimensional construct, research on “poor” self-control suggests that multiple dimensions may be necessary to capture aspects of self-control. The current study sought to create a new brief survey measure of top-down self-control that differentiates between self-control capacity, internal motivation, and external motivation. Items were adapted from the Brief Self-Control Scale (BSCS; Tangney, Baumeister, & Boone, 2004) and were administered through two online surveys to 347 undergraduate students enrolled in introductory psychology courses at Arizona State University. The Self-Control Motivation and Capacity Survey (SCMCS) showed strong evidence of validity and reliability. Exploratory and confirmatory factor analyses supported a 3-factor structure of the scale consistent with the underlying theoretical model. The final 15-item measure demonstrated excellent model fit, chi-square = 89.722 p=.077, CFI = .989, RMSEA = .032, SRMR = .045. Despite several limitations including the cross-sectional nature of most analyses, self-control capacity, internal motivation, and external motivation uniquely related to various self-reported behavioral outcomes, and accounted for additional variance beyond that accounted for by the BSCS. Future studies are needed to establish the stability of multiple dimensions of self-control, and to develop state-like and domain-specific measures of self-control. While more research in this area is needed, the current study demonstrates the importance of studying multiple aspects of top-down self-control, and may ultimately facilitate the tailoring of interventions to the needs of individuals based on unique profiles of self-control capacity and motivation.
ContributorsPapova, Anna (Author) / Corbin, William R. (Thesis advisor) / Karoly, Paul (Committee member) / Brewer, Gene (Committee member) / Arizona State University (Publisher)
Created2016
Description
The ability to preferentially encode and later retrieve valuable information amidst a plethora of miscellaneous information is an essential aspect of human memory. Several hypotheses have been suggested to explain the enhanced ability to successfully encode high value items. These include the hypothesis that the prefrontal executive control processes are engaged for valuable information, producing elaborative rehearsal strategy. Another hypothesis is that greater attentional resources are allocated to higher value items via the reward driven mid-brain dopamine systems interacting with hippocampal and cortical areas to produce enhanced memory. To further understand the neural mechanisms of value on memory, electroencephalogram data under a value-directed remembering paradigm (VDR) was analyzed for oscillatory activity. During the task, participants encoded words assigned a different point value with the instruction to maximize the point value of recognized words during test. To analyze frequency activity during encoding, conditions of subsequent memory as subjective responses of either recollection (i.e., “remember”) and familiarity (i.e., “know”) were assessed. A possible way to observe the allocation of attention resources in the brain are alpha oscillations (8-15 Hz) which are thought to underlie this process. Participants demonstrated superior memory for high versus low value point items. Following the hypothesis that there is a greater recruitment of attentional resources for high value information, alpha oscillatory power in the occipital/temporal cortex displayed significantly more desynchronization for high value compared to low value conditions during encoding. As well, successful retrieval compared with unsuccessful retrieval and subsequent “remember” or “know” conditions resulted in a qualitatively different, more sustained desynchronization of alpha and other unanticipated frequency band oscillations during encoding that are discussed. Taken together, these findings support previous research for alpha-band desynchronization during encoding items of value into memory and potentially open paths to decouple value and memory driven processes.
ContributorsWilliams, Cole (Author) / Brewer, Gene (Thesis advisor) / McClure, Samuel (Committee member) / Blais, Chris (Committee member) / Arizona State University (Publisher)
Created2022
Description
Behavioral, electrophysiological, and neuroimaging evidence has demonstrated that multiple object tracking (MOT) tasks draw upon visual perception, attention, and working memory cognitive processes. Functional neuroimaging studies identified the middle temporal visual area (MT+/V5) as one of several brain regions associated with MOT in humans. MT+/V5 is thought to be responsible for processing motion from visual information, regulating smooth pursuit eye movements, and encoding memory for motion. However, it is unclear how MT+/V5 interacts with attention and working memory performance processes during MOT. To investigate this question, the right MT+/V5 region was identified in 14 neurotypical subjects using structural magnetic resonance imaging (sMRI). The right MT+/V5 was stimulated using intermittent theta-burst stimulation (iTBS), continuous theta-burst stimulation (cTBS), and sham transcranial magnetic stimulation (TMS) using a within-subjects design. Average MOT performance was measured before and 5-min, 30-min, and 60-min after each stimulation protocol. There was no significant difference in average MOT performance across time, regardless of the stimulation condition.
ContributorsAlucard, Myles (Author) / Duran, Nicholas (Thesis advisor, Committee member) / Brewer, Gene (Thesis advisor, Committee member) / Burleson, Mary (Committee member) / Arizona State University (Publisher)
Created2023
Description
The present study aimed to compare brain activity changes related to proactive and reactive control strategies in patients with Parkinson’s disease during “On” levodopa and “Off” levodopa conditions. The study consisted of two participants who had received a prior diagnosis of Parkinson’s Disease. The participants completed AX-CPT task as a measure of attention control in two sessions: a) “On Levodopa” and b) “Off Levodopa” while they were in the fMRI scanner. Prior to the analysis, the T1- weighted anatomical scan images and the BOLD multiband functional images of both the participants were BIDS (Brain Imaging Data Structure) validated and preprocessed using the standard FMRIPrep pipeline. The imaging data was then analyzed using SPM12 (Statistical parametric mapping) software. Individual-level analysis of the imaging data was conducted by creating General Linear models for both the participants on “ON” and “OFF” levodopa conditions. The BOLD responses were compared using AY>BY and BX > BY contrasts. Where BX >, BY contrast, measured BOLD activity related to reactive control strategy and AY> BY contrast measured BOLD activity related to the proactive control strategy. It was observed that participants tended towards reactive control strategy in both “On” and “Off” levodopa conditions.
ContributorsDatta, Kalyani (Author) / Brewer, Gene (Thesis advisor) / Braden, B. Blair (Committee member) / Peterson, Daniel (Committee member) / Arizona State University (Publisher)
Created2022
Description
Dopamine neurons are essential for several aspects of cognition. Several decades of Parkinson’s Disease (PD) research have revealed that the deterioration of these neurons is associated with a wide range of cognitive deficits such as attention, motor coordination, and memory. The diversity of these deficits is a demonstration of the structural and functional heterogeneity within the dopaminergic system; projections from the substantia nigra and the ventral tegmental area to striatum have targets in the frontal and medial temporal cortices. It is known that prospective memory is negatively affected by PD, but whether the deficits originate from pathways that support attention, retrospective memory, working memory, and/or motor control has not yet been determined. For the current study, the goal is to estimate the structural integrity of these pathways by using diffusion-imaging analysis to then correlate these estimates with prospective memory performance within a standard event-based task. Two participant data sets were reported in the current study and compared with the global and target fractional anisotropy as well as seed connectivity. All the results reported here are preliminary.
ContributorsTerry, Jade (Author) / Brewer, Gene (Thesis advisor) / Ofori, Edward (Thesis advisor) / McClure, Samuel (Committee member) / Arizona State University (Publisher)
Created2022
Description
The ability to inhibit a planned but inappropriate response, and switch to executing a goal-relevant motor response, is critically important for the regulation of motor behaviors. Inhibition and switching could be mediated by various control mechanisms. Proactive control uses contextual information (cues) to plan the response for the target stimulus (probe) based on the expectation of a response inhibition or switching stimulus combination. Previous work has reported the involvement of several brain areas associated with proactive inhibition and switching, e.g., dorsolateral prefrontal cortex, anterior cingulate cortex, inferior frontal junction, and pre-supplementary motor area. However, how these areas interact and their functional role in different types of cognitive control is still debated. An AX-version of the continuous performance task (AX-CPT) was used to examine proactive inhibition and switching of motor actions. In a typical AX-CPT trial, a contextual cue stimulus is presented, followed by a probe stimulus after a specific inter-stimulus interval. As part of a trial sequence, if a target cue and target probe are presented, a target response is to be provided when the probe is observed. Otherwise, a non-target response is to be provided for all other stimuli. A behavioral switching AX-CPT experiment (48 subjects) was conducted to explore the parameters that induce a proactive shift in the motor response. Participants who performed the AX-CPT task with relatively shorter interstimulus interval predominantly and consistently exhibited proactive control behavior. A follow-up pilot study (3 subjects) of response inhibition versus response switching AX-CPT was performed using 256-channel high-density electroencephalography (HD-EEG). HD-EEG was used to identify the time course of cortical activation in brain areas associated with response inhibition. It was observed that one out of three participants used a proactive strategy for response switching based on probe response error and probe response reaction time. Instantaneous amplitude spatial maps obtained from HD-EEG revealed cortical activity corresponding to conflict between proactively-prepared incorrect responses and reactively-corrected goal-relevant responses after the probe was presented.
ContributorsMysore, Archana Shashidhar (Author) / Santello, Marco (Thesis advisor) / Blais, Christopher (Committee member) / Brewer, Gene (Committee member) / Tillery, Stephen Helms (Committee member) / Arizona State University (Publisher)
Created2020
Description
This study examined the effects of different constructed response prompts and text types on students’ revision of misconceptions, comprehension, and causal reasoning. The participants were randomly assigned to prompt (self-explain, think-aloud) and text type (refutational, non-refutational) in a 2x2, between-subjects design. While reading, the students were prompted to write responses at regular intervals in the text. After reading, students were administered the conceptual inventory of natural selection (CINS), for which a higher score indicates fewer misconceptions of natural selection. Finally, students were given text comprehension questions, and reading skill and prior knowledge measures. Linear mixed effects (LME) models showed that students with better reading skill and more prior knowledge had a higher CINS score and better comprehension compared to less skilled students, but there were no effects of text type or prompt. Linguistic analysis of students’ responses demonstrated a relationship of prompt, text, and reading skill on students’ causal reasoning. Less skilled students exhibited greater causal reasoning when self-explaining a non-refutational text compared to less skilled students prompted to think-aloud, and less skilled students who read the refutational text. The results of this study demonstrate a relationship between reading skill and misconceptions in natural selections. Furthermore, the linguistic analyses suggest that less skilled students’ causal reasoning improves when prompted to self-explain.
ContributorsWatanabe, Micah (Author) / McNamara, Danielle S. (Thesis advisor) / Brewer, Gene (Committee member) / Firetto, Carla (Committee member) / Arizona State University (Publisher)
Created2020
Description
Statistical word learning (SWL) has been proposed and tested as a powerful mechanism for word learning under referential ambiguity. Learners are adept at resolving word-referent ambiguity by calculating the co-occurrences between words and referents across ambiguous scenes. Despite the generalizability of such capacity, it is less clear which underlying factors may play a role in SWL, such as learners’ language experience and individual differences of working memory. The current study therefore asked two questions: 1) How do learners of different language experience (monolinguals and bilinguals) approach SWL of different mapping types–when each referent has one name (1:1 mapping) or two names (2:1 mapping)? and 2) How do working memory capacities (spatial and phonological) play a role in SWL by mapping type? In this pre-registered study (OSF: https://osf.io/mte8s/), 69 English monolinguals and 88 bilinguals completed two SWL tasks (1:1 and 2:1 mapping), a symmetry span task indexing spatial working memory, and a listening span task indexing phonological working memory. Results showed no differences between monolinguals and bilinguals in SWL of both mapping types. However, spatial and phonological working memory positively predicted SWL regardless of language experience, but only in 1:1 mapping. The findings show a dissociation of working memory’s role in SWL of different mapping types. The study proposes a novel insight into a theoretical debate underlying statistical learning mechanisms: learners may adopt more explicit processes (i.e. hypothesis-testing) during 1:1 mapping but implicit processes (i.e. associative learning) during 2:1 mapping. Future studies can locate memory-related brain areas during SWL to test out the proposal.
ContributorsLi, Ye (Author) / Benitez, Viridiana (Thesis advisor) / Goldinger, Stephen (Committee member) / Brewer, Gene (Committee member) / Arizona State University (Publisher)
Created2022