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Description
Theories of interval timing have largely focused on accounting for the aggregate properties of behavior engendered by periodic reinforcement, such as sigmoidal psychophysical functions and their scalar property. Many theories of timing also stipulate that timing and motivation are inseparable processes. Such a claim is challenged by fluctuations in and out of states of schedule control, making it unclear whether motivation directly affects states related to timing. The present paper seeks to advance our understanding of timing performance by analyzing and comparing the distribution of latencies and inter-response times (IRTs) of rats in two fixed-interval (FI) schedules of food reinforcement (FI 30-s and FI 90-s), and in two levels of food deprivation. Computational modeling revealed that each component was well described by mixture probability distributions embodying two-state Markov chains. Analysis of these models revealed that only a subset of latencies are sensitive to the periodicity of reinforcement, and pre-feeding only reduces the size of this subset. The distribution of IRTs suggests that behavior in FI schedules is organized in bouts that lengthen and ramp up in frequency with proximity to reinforcement. Pre-feeding slowed down the lengthening of bouts and increased the time between bouts. When concatenated, these models adequately reproduced sigmoidal FI response functions. These findings suggest that behavior in FI fluctuates in and out of schedule control; an account of such fluctuation suggests that timing and motivation are dissociable components of FI performance. These mixture-distribution models also provide novel insights on the motivational, associative, and timing processes expressed in FI performance, which need to be accounted for by causal theories of interval timing.
ContributorsDaniels, Carter W (Author) / Sanabria, Federico (Thesis advisor) / Brewer, Gene (Committee member) / Wynne, Clive (Committee member) / Arizona State University (Publisher)
Created2015
Description
Childhood Apraxia of Speech (CAS) is a severe motor speech disorder that is difficult to diagnose as there is currently no gold-standard measurement to differentiate between CAS and other speech disorders. In the present study, we investigate underlying biomarkers associated with CAS in addition to enhanced phenotyping through behavioral testing. Cortical electrophysiological measures were utilized to investigate differences in neural activation in response to native and non-native vowel contrasts between children with CAS and typically developing peers. Genetic analysis included full exome sequencing of a child with CAS and his unaffected parents in order to uncover underlying genetic variation that may be causal to the child’s severely impaired speech and language. Enhanced phenotyping was completed through extensive behavioral testing, including speech, language, reading, spelling, phonological awareness, gross/fine motor, and oral and hand motor tasks. Results from cortical electrophysiological measures are consistent with previous evidence of a heightened neural response to non-native sounds in CAS, potentially indicating over specified phonological representations in this population. Results of exome sequencing suggest multiple genetic variations contributing to the severely affected phenotype in the child and provide further evidence of heterogeneous genomic pathways associated with CAS. Finally, results of behavioral testing demonstrate significant impairments evident across tasks in CAS, suggesting underlying sequential processing deficits in multiple domains. Overall, these results have the potential to delineate functional pathways from genetic variations to the brain to observable behavioral phenotypes and motivate the development of preventative and targeted treatment approaches.
ContributorsVose, Caitlin (Author) / Peter, Beate (Thesis advisor) / Liu, Li (Committee member) / Brewer, Gene (Committee member) / Arizona State University (Publisher)
Created2018
Description
Muslim refugees and Muslim immigrants, and undocumented immigrants have been a prominent part of American culture and have been woven into the history of the United States. Both group's presence in the United States has elicited rhetoric from U.S citizens and U.S public officials. One may infer that the narrative of Muslim refugees and Muslim immigrants overlaps the narrative of undocumented immigrants living in the United States. Both Muslim refugees and immigrants as well as unauthorized immigrants, are criminalized in the United States, or are associated to crime by default of their faith and or their legal status. The association that Muslim refugees and Muslim immigrants, and undocumented immigrants have with crime, based on their rhetoric, has elicited a policy from the United States government as well. The United States government has responded to a presumed threat that both groups pose to U.S. citizens and the nation by means of aggressive legislation, both local and federal. In this research paper, past and present discourse on Muslim refugees and Muslim immigrants and undocumented immigrants was analyzed to determine each of the group's narrative; the mainstream media, newspapers and photographic images, was also considered to determine the narrative of both groups. Based on the discourse on Muslim refugees and Muslim immigrants and on undocumented immigrants, the media portrayal of both groups, and on the change of public policy one may assert that the narratives of both groups overlaps; as both Muslim refugees and immigrants and unauthorized immigrants are seen as a possible threat to the American people.
ContributorsGalvan, Brigitte Magdalena (Author) / Doty, Roxanne (Thesis director) / Magaña, Lisa (Committee member) / School of Politics and Global Studies (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
Trust was measured for a target profile that varied the target's religion and costly signaling behavior. Subjects were primed with a threat, romance, or neutral response previous to viewing the profile to determine if this had any effect on their trust ratings of the target. Participants were drawn from MTurk with ages ranging from 18 to 75 (M= 33.2) and various religious backgrounds (including 210 Christians, 190 atheists/agnostics, and 92 other religious believers). Participants were presented with the threat, romance, or neutral vignette, shown the target profile, and asked to rate the target's trustworthiness. There was no main effect of the vignette condition (p = .088) or costly signaling (p = .099) on the target's trustworthiness. There was a main effect of target religion (p = .006) wherein the Muslim target was trusted more than the Catholic target. These findings do not replicate previous findings on religion, costly signaling, and trust.
ContributorsBesaw, Courtney Michelle (Author) / Cohen, Adam (Thesis director) / Brewer, Gene (Committee member) / School of Human Evolution and Social Change (Contributor) / Department of Psychology (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
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
Adults with autism spectrum disorder (ASD) face heightened risk of co-occurring psychiatric conditions, especially depression and anxiety disorders, which contribute to seven-fold higher suicide rates than the general population. Mindfulness-based stress reduction (MBSR) is an 8-week meditation intervention centered around training continuous redirection of attention toward present moment experience, and has been shown to improve mental health in autistic adults. However, the underlying therapeutic neural mechanisms and whether behavioral and brain changes are mindfulness-specific have yet to be elucidated. In this randomized clinical trial, I utilized functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) to characterize fMRI functional activity (Study 1) and connectivity (Study 2) and EEG neurophysiological (Study 3) changes between MBSR and a social support/relaxation education (SE) active control group. Study 1 revealed an MBSR-specific increase in the midcingulate cortex fMRI blood oxygen level dependent signal which was associated with reduced depression. Study 2 identified nonspecific intervention improvements in depression, anxiety, and autistic, and MBSR-specific improvements in the mindfulness trait ‘nonjudgment toward experience’ and in the executive functioning domain of working memory. MBSR-specific decreases in insula-thalamus and frontal pole-posterior cingulate functional connectivity was associated with improvements in anxiety, mindfulness traits, and working memory abilities. Both MBSR and SE groups showed decreased amygdala-sensorimotor and frontal pole-insula connectivity which correlated with reduced depression. Study 3 consisted of an EEG spectral power analysis at high-frequency brainwaves associated with default mode network (DMN) activity. Results showed MBSR-specific and nonspecific decreases in beta- and gamma-band power, with effects being generally more robust in the MBSR group; additionally, MBSR-specific decreases in posterior gamma correlated with anxiolytic effects. Collectively, these studies suggest: 1) social support is sufficient for improvements in depression, anxiety, and autistic traits; 2) MBSR provides additional benefits related to mindfulness traits and working memory; and 3) distinct and shared neural mechanisms of mindfulness training in adults with ASD, implicating the salience and default mode networks and high-frequency neurophysiology. Findings bear relevance to the development of personalized medicine approaches for psychiatric co-morbidity in ASD, provide putative targets for neurostimulation research, and warrant replication and extension using advanced multimodal imaging approaches.
ContributorsPagni, Broc (Author) / Braden, B. Blair (Thesis advisor) / Newbern, Jason (Thesis advisor) / Davis, Mary (Committee member) / Brewer, Gene (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
Aortic aneurysms and dissections are life threatening conditions addressed by replacing damaged sections of the aorta. Blood circulation must be halted to facilitate repairs. Ischemia places the body, especially the brain, at risk of damage. Deep hypothermia circulatory arrest (DHCA) is employed to protect patients and provide time for surgeons to complete repairs on the basis that reducing body temperature suppresses the metabolic rate. Supplementary surgical techniques can be employed to reinforce the brain's protection and increase the duration circulation can be suspended. Even then, protection is not completely guaranteed though. A medical condition that can arise early in recovery is postoperative delirium, which is correlated with poor long term outcome. This study develops a methodology to intraoperatively monitor neurophysiology through electroencephalography (EEG) and anticipate postoperative delirium. The earliest opportunity to detect occurrences of complications through EEG is immediately following DHCA during warming. The first observable electrophysiological activity after being completely suppressed is a phenomenon known as burst suppression, which is related to the brain's metabolic state and recovery of nominal neurological function. A metric termed burst suppression duty cycle (BSDC) is developed to characterize the changing electrophysiological dynamics. Predictions of postoperative delirium incidences are made by identifying deviations in the way these dynamics evolve. Sixteen cases are examined in this study. Accurate predictions can be made, where on average 89.74% of cases are correctly classified when burst suppression concludes and 78.10% when burst suppression begins. The best case receiver operating characteristic curve has an area under its convex hull of 0.8988, whereas the worst case area under the hull is 0.7889. These results demonstrate the feasibility of monitoring BSDC to anticipate postoperative delirium during burst suppression. They also motivate a further analysis on identifying footprints of causal mechanisms of neural injury within BSDC. Being able to raise warning signs of postoperative delirium early provides an opportunity to intervene and potentially avert neurological complications. Doing so would improve the success rate and quality of life after surgery.
ContributorsMa, Owen (Author) / Bliss, Daniel W (Thesis advisor) / Berisha, Visar (Committee member) / Kosut, Oliver (Committee member) / Brewer, Gene (Committee member) / Arizona State University (Publisher)
Created2020
Description
This study focuses on the properties of binaural beats (BBs) compared to Monaural beats (MBs) and their steady-state response at the level of the Superior Olivary Complex (SOC). An auditory nerve stimulator was used to simulate the response of the SOC. The simulator was fed either BBs or MBs stimuli to compare the SOC response. This was done for different frequencies at twenty, forty, and sixty hertz for comparison of the SOC response envelopes. A correlation between the SOC response envelopes for both types of beats and the waveform resulting from adding two tones together was completed. The highest correlation for BBs was found to be forty hertz and for MBs it was sixty hertz. A Fast Fourier Transform (FFT) was also completed on the stimulus envelope and the SOC response envelopes. The FFT was able to show that within the BBs presentation the envelopes of the original stimuli showed no difference frequency. However, the difference frequency was present in the binaural SOC response envelope. For the MBs, the difference frequency was present within the stimulus and the monaural SOC response envelope.
ContributorsCrawford, Taylor Janay (Author) / Brewer, Gene (Thesis advisor) / Zhou, Yi (Committee member) / Azuma, Tamiko (Committee member) / Arizona State University (Publisher)
Created2021