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Role Of Astrocyte-Derived Extracellular Vesicles In Neuroinflammation Mediated By Drug Abuse, Ke Liao

Theses & Dissertations

Neuronal damage and neuroinflammation is a hallmark feature of HIV-associated neurological disorders (HANDs). Opioids abuse accelerates the incidence and progression of HAND; however, the mechanisms underlying the potentiation of neuropathogenesis by these drugs remain elusive. Extracellular vesicles (EVs) are essential conduits in HIV and drug abuse-mediated synaptodendritic injury and neuroinflammation. Findings from our group have demonstrated that astrocyte-derived EV (ADEV)-miRNA-29b mediates HIV Tat and morphine-induced neuronal injury, thus underscoring the importance of such interactions in NeuroHIV.

Besides, HIV Tat and morphine-mediated synaptodendritic injury via ADEVs, we are also interested in whether ADEVs contributes to neuroinflammation. Microglia are critical players in …

Functional Analysis In The Home Setting Of An Older Adult With Neurocognitive Disorder, Emily Norton

Masters Theses

Currently within the behavioral gerontology literature there are no published studies that include a functional assessment in the home setting. The primary goal of the present study was to address this gap by conducting a functional analysis on a challenging behavior of an older adult with neurocognitive disorder in the home. This study occurred in two phases. During phase one, researchers conducted an antecedent functional analysis on the bizarre speech of an 81-year-old female with suspected dementia across four conditions (television on, no interactions initiated; television on, interactions initiated; television off, no interactions initiated; television off, interactions initiated). Results from …

The Feedback-Related Negativity Is A Time-Dependent Brain Mechanism That Facilitates Aversive Learning: Implications For The Reinforcement Learning Frn Hypothesis, Eric Rawls

Graduate Theses and Dissertations

Organisms encode rewarding and aversive experiences through reinforcement learning, capitalizing on prediction errors (PEs), which adapt action strategies over time. Computational theories are explicit that PE signals should update action weights continuously over the course of a behavioral task, an important time-dependent variation that is eschewed in traditional neuroscience studies that average over large numbers of trials. I examined variation in reaction times and feedback-locked cortical activity over time as a function of PE to critically examine theories indicating that PE signals drive time-dependent learning. We recorded EEG while participants completed a novel reinforcement task that varied prediction error on …

The Role Of Gamma Oscillations And Cortical Inhibition In The Development Of Working Memory In Adolescence, Christopher P. Walker

Dissertations & Theses (Open Access)

Adolescence is a dynamic period of social, cognitive, and biological changes. In particular, working memory, the ability to actively encode and maintain information over a short period of time, develops early in childhood and gradually increases in capacity and stability during adolescence. The precise neurophysiological mechanism by which working memory capacity increases during adolescence is unclear. The objective of this investigation was to evaluate the role of cortical gamma-band (> 30 Hz) oscillations—which are associated with working memory in adults—for the development of working memory capacity in adolescents, and to identify the extent to which the temporal profile of gamma-aminobutyric …

Functional Dissociations Revealed By Representational Similarity Analysis Of Color-Word Stroop, Michael Freund

Arts & Sciences Electronic Theses and Dissertations

The color-word Stroop task is often used in cognitive neuroscience as a common platform for both theoretical and experimental approaches to cognitive control. Yet traditionally, there has been tension between these two approaches. Theoretical models of Stroop have focused on representation: for example, how distributed and overlapping representations of the two stimulus dimensions (color, word) are prioritized, and how conflict between these dimen- sions is represented and used to regulate control. In contrast, neuroimaging experiments have primarily focused on ‘univariately’ (uniformly) mapping the effects of conflict to par- ticular brain regions. This focus on univariate changes in brain activity limits …

How Perception Of Decision Environment And Future Information Affects Changes In Delay Discounting Rates: Differences Across U.S. And China, Differences Before And After The U.S. 2018 Midterm Elections, Fran Walsh

Masters Theses

In this thesis, I will explore the idea that choices between present, smaller value options and future, larger value options depend on how much individuals trust the future to deliver the reward. Due to this aspect of trust, the individual must build their estimate of trust based on information for their present environment and their future expectations. This estimate of future trust can change across different time points in the same environment (i.e., before and after a national election) and between environments in the same time point (i.e., between two countries experiencing different economic rates of change). In this set …

In Search Of Psychiatric Kinds: Natural Kinds And Natural Classification In Psychiatry, Nicholas Slothouber

Electronic Thesis and Dissertation Repository

In recent years both philosophers and scientists have asked whether or not our current kinds of mental disorder—e.g., schizophrenia, depression, bipolar disorder—are natural kinds; and, moreover, whether or not the search for natural kinds of mental disorder is a realistic desideratum for psychiatry. In this dissertation I clarify the sense in which a kind can be said to be “natural” or “real” and argue that, despite a few notable exceptions, kinds of mental disorder cannot be considered natural kinds. Furthermore, I contend that psychopathological phenomena do not cluster together into kinds in the way that paradigmatic natural kinds (e.g., chemical …

How Do Humans Process Magnitudes? An Examination Of The Neural And Cognitive Underpinnings Of Symbols, Quantities, And Size In Adults And Children, Helen Moriah Sokolowski

Electronic Thesis and Dissertation Repository

A striking way that humans differ from other species is our unique ability to represent and manipulate symbols. This ability to process numerical magnitudes symbolically (e.g., ‘three’, ‘3’) is widely thought to be supported by an ancient system that evolved to process nonsymbolic numerical magnitudes (i.e., quantities). In this thesis, I present four empirical studies to uncover whether symbolic representations are indeed supported by the system that evolved to process quantities, or if symbolic representations are sub-served by a similar but ultimately distinct system.

In experiments 1 and 2, I investigate how the adult brain processes symbols and quantities using …

How Does The Brain Represent Digits? Investigating The Neural Correlates Of Symbolic Number Representation Using Fmri-Adaptation, Celia Goffin

Electronic Thesis and Dissertation Repository

How does the brain represent numerical symbols (e.g., Arabic digits)? Activity in left parietal regions correlates with symbolic number processing. Research with functional resonance imaging adaptation (fMRI-A) indicates that the intraparietal sulcus (IPS) exhibits a rebound (increase in activation) effect when a repeatedly presented number is followed by a new number. Importantly, this rebound effect is modulated by numerical ratio as well as the difference between presented numbers (distance). This ratio-dependent rebound effect could reflect a link between symbolic numerical representation and an approximate number system (ANS). In this doctoral dissertation, fMRI-A is used to investigate mechanisms underlying symbolic number …

Cognitive, Neural, And Educational Contributions To Mathematics Performance: A Closer Look At The Roles Of Numerical And Spatial Skills, Zachary C.K. Hawes

Electronic Thesis and Dissertation Repository

The principal aims of this thesis were to (1) provide new insights into the cognitive and neural associations between spatial and mathematical abilities, and (2) translate and apply findings from the field of numerical cognition to the teaching and learning of early mathematics.

Study 1 investigated the structure and interrelations amongst cognitive constructs related to numerical, spatial, and executive function (EF) skills and mathematics achievement in 4- to 11-year old children (N=316). Results revealed evidence of highly related, yet separable, cognitive constructs. Together, numerical, spatial, and EF skills explained 84% of the variance in mathematics achievement (controlling for chronological age). …

Emotion Processing Deficits In Psychopathy: Does Cueing To Relevant Facial Features Increase Cognitive And Emotional Empathy?, Shawn E. Fagan

Dissertations, Theses, and Capstone Projects

Psychopathy is a multifaceted disorder characterized by a lack of cognitive and emotional empathy. The traditional model of psychopathy divides the disorder into two factors: Factor 1 consists of the interpersonal and affective traits of psychopathy while Factor 2 measures antisocial behaviors and lifestyle choices. The attention-to-the-eyes hypothesis argues that psychopathic individuals have impaired emotion recognition (specifically for fear) due to deficits in orienting attention to salient facial features like the eyes. Psychopathic individuals also display blunted autonomic responding to emotional stimuli, though whether this is due to attention-orienting deficits remains to be clarified. The present project investigated whether empathy-related …

Neural Correlates Of Automatic Emotional Processing And Emotion Regulation In Empathy And Psychopathy-Related Coldheartedness, Danielle Difilipo

Dissertations, Theses, and Capstone Projects

Psychopathy is a personality disorder that is defined, in part, by a lack of empathy. Psychopathy-related empathic deficits have been associated with atypical behavioral and neural responses to emotional facial expressions. Although the mirror neuron system (MNS) has been implicated in empathy, very few studies have examined the role of MNS functioning as it pertains to empathy impairments in psychopathy. Moreover, there is very little empirical research regarding emotion regulation in psychopathy, and specifically whether emotional responses can be intentionally upregulated. The present study sought to clarify whether the MNS is functionally intact in adults with subclinical psychopathic traits, particularly …

Voluntary Oral Methamphetamine Reveals Susceptibilities To Spatial Memory Deficits, Decreased Dopamine Marker Expression And Increased Neuroinflammation In The Hippocampus Of Male And Female Mice, Jorge A. Avila

Dissertations, Theses, and Capstone Projects

Methamphetamine is an addictive illicit psychostimulant that produces lasting neurochemical and behavioral changes. The mechanisms underlying these deficits have been characterized in animal models using extremely high doses. Currently, better translational models are needed to understand the onset and progression of these deficits that more accurately reflect the gradual and voluntary dosing parameters as chosen by an abuser. To that end, a new model of methamphetamine administration, labeled Voluntary Oral Methamphetamine Administration (VOMA), offers a means to examine the progression of neurotoxicity, behavioral deficits, and the addiction process through a voluntary consumption framework.

Female populations show consistent vulnerabilities to methamphetamine, …

Visual Entrainment Of Perception-Related Neural Oscillations As A Mechanism For Maintaining Rhythmic Temporal Expectations Across A Wide Range Of Frequencies, Michael James Gray

Dissertations, Theses, and Capstone Projects

Visual sensitivity fluctuates rhythmically, in-synch with ongoing, EEG-recorded neural oscillations across a wide range of frequencies (~1-25hz). Some recent work has suggested that these perception-related neural oscillations can be entrained by rhythmic visual stimulation. Evidence is also emerging that the entrainment of ongoing oscillations in visual and auditory cortices is involved in rhythmic temporal expectations. In the introduction chapter, I attempt to bridge these bodies of literature and hypothesize that rhythmic visual stimuli automatically entrain ongoing, perception-related neural oscillations and that this mechanism supports the maintenance of rhythmic temporal expectations. Chapters 2 and 3 address this hypothesis from different angles. …

The Interaction Of Attention And Memory On The Reorienting Negativity, John C. Moses

Dissertations, Theses, and Capstone Projects

The three-stage model of distraction asserts that when we are presented with salient but task-irrelevant information, our sensory systems first detect the distracting stimulus by way of sensory memory buffers, which is indicated electrophysiologically by the mismatch negativity (MMN). Following detection, attentional resources are involuntarily allocated towards the processing of the distraction, as represented by the P3a. Finally, attentional resources are shifted away from the distracting stimulus and returned to the task-relevant information, as indicated by the reorienting negativity (RON). A great deal of research has focused on this last step in the model, largely centering around defining the mechanisms …

Using Meditation To Improve Measures Of Attention In Older Adults, Sabrina Ford

Electronic Thesis and Dissertation Repository

Age-related cognitive decline greatly impacts quality of life for older adults. Previous research has indicated that meditation may act as a neuroprotective factor to prevent age-related cognitive decline. This thesis sought to replicate previous findings and investigate if a four-week meditation intervention would improve sustained attention. Participants 60 years and older (n=27, 17 female) were recruited and assigned to a focused-attention (FA) meditation or relaxation group which met for four weeks, three times a week. Resting-state EEG was used to collect individual alpha peak frequency (iAPF) and frontal alpha asymmetry (FAA). The Sustained Attention to Response Task (SART) was also …

Pupil Size Tracks Semantic Ambiguity As Well As Noise, Mason Kadem

Electronic Thesis and Dissertation Repository

Effortful listening is experienced by listeners when speech is hard to understand because it is degraded or masked by environmental noise. Pupillometry (i.e., measure of pupil size) can detect effortful listening: pupil size increases when speech is degraded compared to when it is clear. However, the pupil responds to a range of cognitive demands, including linguistic challenges such as syntactic complexity. Here I investigate whether it responds to the need to disambiguate words with more than one meaning, such as ‘bark’ or ‘bank’. Semantic ambiguity is common in English, and previous work indicates that it imposes a processing load. We …

Improving Stimulus Realism: The Effect Of Visual Dimension On Affective Responding, Shannon Compton

Electronic Thesis and Dissertation Repository

For decades researchers have used 2D stimuli under the assumption that they accurately represent real objects. This assumption has been challenged by recent vision and neuroeconomics research which has found that 2D images can evoke different neural and behavioural responses than real objects. The current study continues this line of research in the field of affective cognitive neuroscience; a field where small effect sizes are common and rapid habituation to affective stimuli used in the lab often occurs. The present study uses realistic 2D and 3D emotional images to determine the impact of visual dimension on affective responding. Subjective ratings …

Investigating The Relationship Between Subcortical And Cortical Auditory Processing, Sonia Varma

Electronic Thesis and Dissertation Repository

The auditory system is highly integrative, with feedforward and feedback connections from periphery to cortex (and stages in between). In order to understand how the different levels of the human auditory system interact, it is necessary to simultaneously measure responses from multiple auditory levels. A novel stimulus was paired with electroencephalography (EEG) in 29 young, normal-hearing participants (17-34 years) to examine interactions among stages of the auditory pathway. Temporal regularity was manipulated by continuously accelerating and decelerating the rate of a click-train stimulus (i.e., ~3.5 Hz frequency modulation of the click rate). Adaptation of the brainstem (cochlear nucleus and inferior …

Neurodevelopmental Outcomes Of Infantile Hydrocephalus: An Fmri Case Study, Ikhlas Ahmed Hashi

Electronic Thesis and Dissertation Repository

Ventricle dilatation caused by infantile hydrocephalus may result in extensive damage of the posterior cortex (parietal and occipital lobes). We hypothesize that pathological changes in the development of the posterior cortex can be linked to non-verbal learning disabilities in children with previous infantile hydrocephalus. This case study will investigate the neurodevelopmental outcomes of 3 treated hydrocephalus patients, when compared to a group of healthy control children (n = 12). Within the hydrocephalus group, patients displayed differences in non-verbal test performance as well as parietal brain activation during an fMRI number comparison task. We associated these differences with clinical variables such …

Impact Of Excitation-Inhibition Balance/Imbalance On Dynamics Of Cortical Neural Networks, Vidit Agrawal

Graduate Theses and Dissertations

The purpose of this research is to study the implications of Excitation/Inhibition balance and imbalance on the dynamics of ongoing (spontaneous) neural activity in the cerebral cortex region of the brain.

The first research work addresses the question that why among the continuum of Excitation-Inhibition balance configurations, particular configuration should be favored? We calculate the entropy of neural network dynamics by studying an analytically tractable network of binary neurons. Our main result from this work is that the entropy maximizes at regime which is neither excitation-dominant nor inhibition-dominant but at the boundary of both. Along this boundary we see there …

Resting State Network Dynamics Across Wakefulness And Sleep, Evan Houldin

Electronic Thesis and Dissertation Repository

The function of sleep is a longstanding mystery of the brain. By contrast, the function of resting state networks (RSNs) is one of its most recent mysteries. The relationship between RSNs and neuronal activity has been unclear since RSNs were discovered during the advent of functional magnetic resonance imaging (fMRI). Somewhat paradoxically, investigating these enigmatic phenomena in parallel can help to illuminate the function of both. The three studies described as part of this thesis all involve an evaluation of RSN dynamics across wakefulness and sleep. They are all based on the same dataset, derived from an experimental paradigm in …

Resedent Study- Reducing Sedentary Behaviour May Slow Cognitive Decline In Older Adults With Mild Cognitive Impairment: A Pilot Study, Kirsten B. Dillon

Electronic Thesis and Dissertation Repository

Physical activity (PA) has been shown to slow down dementia. Unfortunately, older adults spend most of their day in sedentary behaviours (SB). Breaking up prolonged bouts of sitting with intermittent bouts of light intensity PA may reduce glycemic variability in the brain; potentially mitigating cognitive decline. This study investigated how interrupting SB with 10 min bouts of light intensity PA 3x a day would affect mild to moderate cognitive impairment progression (primary outcome) in older adults residing in an assisted living facility. Participants (n=25) were assigned in clusters into a two arm 10-week single site pilot randomized controlled trial. Secondary …

Investigating How Neural Entrainment Relates To Beat Perception By Disentangling The Stimulus-Driven Response, Aaron Wc Gibbings

Electronic Thesis and Dissertation Repository

Beat perception – the ability to perceive a steady pulse in music – is nearly ubiquitous in humans, but the neural mechanisms underlying this ability are unknown. A growing number of electroencephalography (EEG) studies suggest that beat perception is related to neural entrainment, a phenomenon in which cyclic changes in the excitability of populations of neurons synchronize with a rhythmic stimulus. However, the relationship between acoustically-driven and entrainment-driven neural activity is unclear. This thesis presents EEG research that extends our understanding neural entrainment is related to beat perception by characterizing, equating, and finally removing the stimulus-driven response in the neural …

Electrophysiological Correlates Of Natural Language Processing In Children And Adults, Margaret Ugolini

Doctoral Dissertations

To understand the causes of differences in language ability we must measure the specific and separable processes that contribute to natural language comprehension. Specifically, we need measures of the three language subsystems – semantics, syntax, and phonology – as they are used during the comprehension of real speech. Event-Related Potentials (ERPs) are a promising approach to reaching this level of specificity. Previous research has identified distinct ERP effects for each of the subsystems – the N400 to semantic anomalies, the Anterior Negativity and P600 to syntactic anomalies, and the Phonological Mapping Negativity to unexpected speech sounds. However, these studies typically …

Changes In Color Guidance Over The Course Of A Complex Visual Search, Ryan Papargiris

Masters Theses

When searching for an object, we store a mental representation of the target, which guides our search through the use of attention. The effectiveness of this search guidance varies depending on the task and the relationship between target and distractors. With a better understanding of how search guidance changes over time within a trial, we can better compare the differences between experimental conditions. Eye tracking data from a variety of search tasks were analyzed to determine how color guidance varied over the course of the trial. Color guidance for a given fixation was evaluated based on the distance in color …

One Year Change In Cognitive Function In Male And Female Common Marmosets (Callithrix Jacchus), Brianna Healey

Masters Theses

Long term cognitive studies in humans and nonhuman primates such as macaques are difficult because of their long lifespan. The common marmoset (Callithrix jacchus) is a non-human primate who shares with humans many features characteristic of primates, including a complex brain and cognitive function. They also have a short lifespan (~10 years) that makes them a great model in studies of cognitive aging. This study focuses on the rate of decline in cognitive function in male and female marmosets based on performance on reversal learning tasks over 2 years of testing.

We found that marmosets improved their overall …

Sex, Motivation, And Reversal Learning In The Common Marmoset (Callithrix Jacchus), Alyssa Carlotto

Masters Theses

This study examined the relationships between motivation and cognitive performance in male and female common marmosets (Callithrix jacchus). This question was driven by prior data from the Lacreuse lab showing a robust female impairment in reversal learning, as assessed by the number of trials needed to acquire a reversal following a simple discrimination between two stimuli. This thesis tested the hypothesis that the female impairment in reversal learning was mediated by deficits in motivation. Two sets of measures were used to test this hypothesis. I evaluated physical effort via testing on the progressive ratio (PR), a test that …

Relationship Among Neurogenic Orthostatic Hypotension, Cerebral Hemodynamics, And Cognitive Functioning, Lindsay Robinson

Electronic Thesis and Dissertation Repository

Neurogenic orthostatic hypotension (NOH) is characterized by a drop in systolic blood pressure ≥20mmHg or diastolic blood pressure ≥10mmHg within three minutes of upright posture. A large drop in blood pressure can trigger cerebral hypoperfusion, which has been linked to deficits in cognitive function. The current thesis aimed to measure cerebral hemodynamics and cognitive function in 20 NOH patients and 20 controls in the supine and head-up tilt (HUT) positions. Information processing speed (IPS) was assessed using the Symbol-Digit Modalities Test and attention was measured using the Stroop Test. NOH patients had significantly slower IPS in both the supine(p

The Origins And Development Of Visual Categorization, Laura Cabral

Electronic Thesis and Dissertation Repository

Forming categories is a core part of human cognition, allowing us to make quickly make inferences about our environment. This thesis investigated some of the major theoretical interpretations surrounding the neural basis of visual category development. In adults, there are category-selective regions (e.g. in ventral temporal cortex) and networks (which include regions outside traditional visual regions—e.g. the amygdala) that support visual categorization. While there has been extensive behavioural work investigating visual categorization in infants, the neural sequence of development remains poorly understood. Based on behavioral experiments, one view holds that infants are initially using subcortical structures to recognize faces. Indeed, …