Neuroscience and Neurobiology Commons^™

Reexamining Object-Based Visual Attention: Understanding The Nature Of Direction-Dependent Attention Shifts, Adam Joseph Barnas

Theses and Dissertations

Attentional selection is a process by which relevant sensory stimuli are afforded enhanced priority for processing over and above irrelevant sensory stimuli. Object-based attention is a form of selection that leads to preferential processing of visual information contained in/on an attended object versus an unattended object. Observers typically exhibit enhanced performance to a target at an invalidly cued same object location compared to a different-object location, which results in a same object advantage as measured by the response time (RT) difference between these two target locations. A growing body of research has shown that object-based effects are small, inconsistent, and …

An Autism-Causing Variant Misregulates Selective Autophagy To Alter Axon Targeting And Behavior, Tyler Buddell

Theses and Dissertations

Neurodevelopmental disorders cause debilitating disruptions to the cellular mechanisms that underlie development of the brain. Unfortunately, the complexities of neurodevelopmental disorders make them difficult to study, and the molecular mechanisms perturbed by these disorders remain elusive. Better understanding of neurodevelopmental mechanisms, and the related genes involved, will likely yield new insight into neurodevelopmental disorders. A gene that has been associated with a number of neurodevelopmental disorders is the calcium voltage-gated channel subunit alpha1 C (CACNA1C) gene. Common and rare variants of the CACNA1C gene have been associated with autism and other neurodevelopmental disorders including schizophrenia, bipolar disorder and ADHD. However, …

Investigating The Contribution Of Instance-Reliant Learning In Visuomotor Adaptation And Its Generalization, Shancheng Bao

Theses and Dissertations

Motor adaptation has been of great interest in the past two decades as it reflects how movement skills are acquired and consolidated by the nervous system. In our recent studies, instance-reliant learning is considered as an essential component of visuomotor adaptation, since it plays a unique role in fast and automatized control of movement output. The goal of this dissertation is to investigate the nature of instance-reliant learning on two aspects: to determine the differential contributions of algorithmic learning and instance-reliant learning to visuomotor adaptation; and to determine the nature of movement instance involved in visuomotor adaptation and its generalization …

Evaluation Of Cognitive Control Using Non-Gaussian Reaction Time Distributions In Fractionated Executive Function Tasks, Dmitriy Kazakov

Theses and Dissertations

The present study seeks to further investigate and refine the three-factor model of executive function (EF; Inhibition, Shifting, and Monitoring/Updating) known as the unity/diversity framework (Miyake et al., 2000). Past work in this area utilized “power” tasks that prioritize accuracy and difficulty, but real-world problem-solving incentivizes quick and efficient solutions. Ten computerized reaction time (RT) tasks: four elementary cognitive tasks (ECTs; Jensen, 1987; Santos, 2016) with progressively increasing task demands and six EF tasks. The ratio scale of RT necessitated the use of non-Gaussian statistics to better describe distribution shape, while diffusion modeling (DM; Ratcliff, 1978) was used to interpret …

Cannabis-Using Youth Demonstrated Blunted Rostral Anterior Cingulate Cortex Activation, But Normal Functional Connectivity, During An Emotional Go/No-Go Task, Kristin Elizabeth Maple

Theses and Dissertations

Cannabis use has been associated with deficits in self-regulation, including inhibitory control. Cannabis users have previously exhibited both structural and functional deficits in the rostral anterior cingulate cortex (rACC), a region involved in self-regulation of emotional response and inhibitory control. The present study aimed to examine whether abstinent cannabis users demonstrated abnormal functional activation and connectivity of the bilateral rACC during an emotional inhibitory processing task, and whether gender moderated these relationships. The study also aimed to examine whether bilateral rACC activation and connectivity in cannabis users was related to perceived stress. It was hypothesized that cannabis users would exhibit …

White Matter Integrity In Individuals At-Risk For Ptsd Development: A Longitudinal Investigation, Carissa Weis

Theses and Dissertations

Trauma exposure is prevalent and while most are resilient, some go on to develop post-traumatic stress disorder (PTSD)—an anxiety-related disorder that results from traumatic experience. The brain changes that result from traumatic experience and PTSD are not well understood. Further, little is known about what distinguishes those who are resilient after trauma from those at risk for developing PTSD. Previous work indicates white matter integrity may be a useful biomarker in predicting PTSD and researchers have found changes in the integrity of three white matter tracts—the cingulum bundle, corpus callosum (CC), and uncinate fasciculus (UF)—in the aftermath of trauma. However, …

Memory-Based Viewing: A Potential Marker Of Pathological Aging, Jenna Blujus

Theses and Dissertations

Markers of cognitive impairment are needed to distinguish normal from pathological aging prior to the onset of clinical symptomology to improve Alzheimer’s disease (AD) treatment or prevention efforts. AD pathology is believed to develop years or even decades prior to diagnosis in medial temporal lobe subregions that provide input to the hippocampus (Braak & Braak, 1991), disrupting the ability of the hippocampus to bind individual elements of an experience to form cohesive memory representations. Eye movement behavior is a sensitive index of learning and effects of memory on eye movements have been shown to emerge rapidly (within 500-750ms of stimuli …

Memory-Based Viewing: A Potential Marker Of Pathological Aging, Jenna Blujus

Theses and Dissertations

Markers of cognitive impairment are needed to distinguish normal from pathological aging prior to the onset of clinical symptomology to improve Alzheimer’s disease (AD) treatment or prevention efforts. AD pathology is believed to develop years or even decades prior to diagnosis in medial temporal lobe subregions that provide input to the hippocampus (Braak & Braak, 1991), disrupting the ability of the hippocampus to bind individual elements of an experience to form cohesive memory representations. Eye movement behavior is a sensitive index of learning and effects of memory on eye movements have been shown to emerge rapidly (within 500-750ms of stimuli …

White Matter Integrity In Individuals At-Risk For Ptsd Development: A Longitudinal Investigation, Carissa Weis

Theses and Dissertations

Trauma exposure is prevalent and while most are resilient, some go on to develop post-traumatic stress disorder (PTSD)—an anxiety-related disorder that results from traumatic experience. The brain changes that result from traumatic experience and PTSD are not well understood. Further, little is known about what distinguishes those who are resilient after trauma from those at risk for developing PTSD. Previous work indicates white matter integrity may be a useful biomarker in predicting PTSD and researchers have found changes in the integrity of three white matter tracts—the cingulum bundle, corpus callosum (CC), and uncinate fasciculus (UF)—in the aftermath of trauma. However, …

Auditory And Contextual Contributions To Memory Lability And Synaptic Destabilization In The Amygdala, Nicole Christine Ferrara

Theses and Dissertations

Pavlovian fear conditioning provides a way to investigate memory formation and retrieval. During fear conditioning, a conditional stimulus (CS) is paired with an aversive outcome and the CS acquires aversive value over several pairings. The CS may then be presented during a retrieval session where fear responding is measured as an indicator of memory strength. Retrieval sessions may allow for the incorporation of new information into the original memory trace by destabilizing amygdala synapses. However, the specific circuits and neural inputs that contribute to memory lability and synaptic destabilization during a retrieval session are poorly understood. Previous work has shown …

Hpa Axis Genetic Variation And Life Stress Influences On Functional Connectivity In Resting State Networks, Tara Ann Miskovich

Theses and Dissertations

Stressful or traumatic experiences are a key risk factor for developing psychopathology, primarily through the impact that chronic stress has on hypothalamic-pituitary-adrenal (HPA) axis functioning. The HPA axis regulates the stress response but can become dysregulated with chronic activation and impact brain functioning. In addition to environmental stressors, genetic variation in genes in the HPA axis appear to influence HPA axis functioning and is also related to disruption in brain functioning, particularly in the context of high life stress. The current study focused on examining potential mechanisms through which trauma and stress interacts with HPA axis genes to impact key …

Baked And Buzzed: Investigating The Influence Of Co-Use Of Cannabis And Alcohol On White Matter Integrity In Emerging Adults, Natasha E. Wright

Theses and Dissertations

Objective: Growing evidence suggests alcohol and cannabis use independently alter neural structure and functioning, particularly during sensitive developmental time periods such as adolescence and emerging adulthood. However, there has been minimal investigation into the effects co-occurring use of these two substances, despite preliminary evidence of unique acute and psychopharmacological changes due to using alcohol and cannabis together.

Method: Data drawn from the IDEAA Consortium was utilized to assess white matter integrity as measured by FreeSurfer’s TRACULA in emerging adults (n=192; 16-27 years old). Timeline Follow-Back was used to calculate past month cannabis use, alcohol use, co-use days, binge alcohol episode, …

Abnormal Reward Processing And Visual Selective Attention: An Event-Related Potential Investigation With Remitted Depressed Adults, Kevin Haworth

Theses and Dissertations

Feedback, rewarding and non-rewarding, received from the environment can facilitate learning, influence motivation and shape behavior (Skinner, 1963; Thorndike, 1898). Recent research has indicated that reward can also enhance cognitive processes such as visual selective attention (Anderson, Laurent, & Yantis, 2011a; Anderson, Laurent, & Yantis, 2011b; Della Libera, Perlato, & Chelazzi, 2011; Krebs, Boehler, Egner, & Woldorff, 2011). Depression is one of the most common, debilitating, and costly forms of mental illness (Katon, 1996; Kessler et al., 2005; Mathers, Fat, & Boerma, 2008) and has been characterized by reduced responsiveness to reward (Henriques, Glowacki, & Davidson, 1994; Henriques & Davidson, …

The Effects Of G-Protein-Coupled Estrogen Receptor (Gper) On Cell Signaling, Dendritic Spines, And Memory Consolidation In The Female Mouse Hippocampus, Jae Kyoon Kim

Theses and Dissertations

One of the most seminal findings in the literature on hormones and cognition is that the potent estrogen 17β-estradiol (E2) significantly increases the density of dendritic spines on pyramidal neurons in the CA1 region of the dorsal hippocampus (DH). However, the extent to which this E2-induced increase in hippocampal spinogenesis is necessary for memory formation remains unclear. The memory-enhancing effects of E2 in the DH can be mediated by intracellular estrogen receptors (ERs) or by the membrane-bound ER called G-protein coupled estrogen receptor (GPER). We previously reported that infusion of a GPER agonist, G-1, into the DH of ovariectomized female …

Structural And Functional Brain Connectivity In Middle-Aged Carriers Of Risk Alleles For Alzheimer's Disease, Laura Korthauer

Theses and Dissertations

Single nucleotide polymorphisms (SNPs) in APOE, COMT, BDNF, and KIBRA have been associated with age-related memory performance and executive functioning as well as risk for Alzheimer’s disease (AD). The purpose of the present investigation was to characterize differences in brain functional and structural integrity associated with these SNPs as potential endophenotypes of age-related cognitive decline. I focused my investigation on healthy, cognitively normal middle-aged adults, as disentangling the early effects of healthy versus pathological aging in this group may aid early detection and prevention of AD. The aims of the study were 1) to characterize SNP-related differences in functional connectivity …

Neural Correlates Of Memory Decisions Made In The Face Of Conflict, Elaine Mahoney

Theses and Dissertations

We’ve all experienced moments where, for some reason or another, we don’t want to reveal to others what we truly know. The current experiment investigated questions about the behavioral and neural correlates of these types of memory decisions made in the face of a conflicting goal. Participants in this experiment studied several scene-face pairs and were tested with three-face displays preceded by studied scene cues. They were instructed to indicate whether the three-face display contained the matching associate or not. Critically, half of the participants were instructed to simulate feigned memory impairment (i.e. simulators), while the remainder were instructed to …

How Does Anxiety Affect Cognitive Control? Proactive And Reactive Control Under State Anxiety, Youcai Yang

Theses and Dissertations

Cognitive control is a construct that prioritizes how we process stimuli and information and execute behaviors to flexibly and efficiently adapt to internal goals and external environmental changes. A recent theory, the Dual Mechanism of Control (DMC), distinguishes this phenomenon by two distinct cognitive control operations: proactive control and reactive control (Braver, 2012). Anxiety increases the allocation of attentional and working memory resources to threat-related stimuli, which impairs cognitive performance (Sarason, 1988), but additional work is needed to assess how anxiety impacts these two distinct forms of cognitive control. In this study, I examined how state anxiety affected proactive control, …

Rescuing Age-Related Proteolysis Deficits With Methylene Blue, Shane E. Pullins

Theses and Dissertations

The average lifespan is constantly increasing with the advent of new medical techniques, and age-related cognitive decline is becoming a prevalent societal issue. Even during healthy aging, humans and rats exhibit progressive deficits in episodic/declarative memory. In laboratory rats, age-related memory impairment can be assessed with trace fear conditioning (TFC). Recent research implicates ubiquitin proteasome system-mediated protein degradation in the synaptic plasticity supporting memory formation and retrieval. In rats, aging leads to decreased basal proteolytic activity in brain structures known to support the acquisition and retrieval of trace fear memories, and our preliminary data suggests activity-dependent proteasome activity declines in …

The Role Of Hippocampal And Medial Prefrontal Interactions In The Estrogenic Regulation Of Memory, Jennifer Tuscher

Theses and Dissertations

Dendritic spine plasticity is thought to be essential for the formation and storage of memories. The sex-steroid hormone 17-estradiol (E2) increases dendritic spine density in 2 brain regions necessary for memory formation, the dorsal hippocampus (DH) and medial prefrontal cortex (mPFC), but the mechanisms through which it does so remain largely unknown. Further, the extent to which these brain regions interact to mediate E2’s effects on memory is also unclear. Recently, we found that infusion of E2 directly into the DH also increases dendritic spine density in the DH and mPFC, and that these effects depend upon rapid activation of …

Sex Differences In Differential Fear Conditioning During The Acquisition And Consolidation Of Learned Safety, David Sylvan Reis

Theses and Dissertations

The ability to distinguish between threatening and non-threatening situations requires careful regulation of behavioral and physiological responses to stress and fear. Deficits in fear regulation are maladaptive and can lead to the development of anxiety disorders such as PTSD. Women are nearly twice as likely to develop PTSD as are men and laboratory animal studies have shown facilitated fear acquisition, resistance to fear extinction, deficits in extinction retention and impaired discrimination between danger and safety cues in females. Taken together this suggests a propensity for reduced inhibitory control over fear responding in females. Here we investigate the mechanisms underlying fear …

Investigating The Functional Connectivity Of The Bed Nucleus Of The Stria Terminalis During Conditions Of Threat And Safety Using High Resolution 7 Tesla Fmri, Walker Scott Pedersen

Theses and Dissertations

An influential model of the extended amygdala defines fear as the immediate response to phasic threat and anxiety as the prolonged response to unpredictable or sustained threat (Davis, Walker, Miles & Grillon, 2010). This model proposes that in response to unpredictable threat, the centromedial amygdala (CeA) activates the bed nucleus of the stria terminalis (BNST), which coordinates the anxiety response, and, in turn, inhibits the CeA. Connectivity between the BNST and both the basolateral amygdala (BLA) and hippocampus may also play an important role in the coordination of the anxiety response (Davis et al., 2010; Herman et al., 2003; Zhu, …

Electrophysiological And Morphological Characterization Of Neurons In The Granular Retrosplenial Cortex, Andrew Nicholas Nye

Theses and Dissertations

The retrosplenial cortex (RSC) is a centrally located brain region that has reciprocal connections with several brain regions important for memory, including the prefrontal cortex, para-hippocampal region, hippocampal formation, and rhinal cortices. The RSC is also well connected with structures important for sensory processing, including the parietal cortex, thalamus, and visual cortices. Due to this connectivity, and early evidence that suggests the RSC plays a critical role in learning and memory, the region has recently gained much more research attention. Early studies found that patients with brain damage that includes the RSC have difficulty with verbal and visual information, retrieving …

Visually-Guided Reaching Under Varying Cognitive And Motor Demand In Young Adult Females With A History Of Concussions, Christopher James Fueger

Theses and Dissertations

Every day, vision guides one’s actions to help one successfully navigate through a complex environment. When our visual and motor systems interact efficiently, we may not fully appreciate how flawless and beneficial this process can be to our daily functioning. Yet, one’s available neural resources needed to successfully perform visually-guided movements do have limits. When an individual suffers a brain injury, such as a concussion, the available resources may be compromised. Examining the extent of this decreased resource pool requires challenging the cognitive abilities enough to observe a behavioral deficit. The purpose of this study was to examine the long-term …

Development Of Mechanosensory Innervation In The Frog, Xenopus Laevis, Peter Andrew Feuk

Theses and Dissertations

ABSTRACT

DEVELOPMENT OF MECHANOSENSORY INNERVATION IN THE FROG, XENOPUS LAEVIS

by

Peter Feuk

The University of Wisconsin-Milwaukee, 2017

Under the Supervision of Dr. R. David Heathcote

This study aims to investigate whether a specific target cell in the epidermis of the African clawed frog, Xenopus laevis, guides the initial outgrowth and pattern of Rohon-Beard (RB) cells and their survival. RB cells are primary mechanosensory neurons present during the early developmental stages of X. laevis. These neurons provide sensory input to the frog throughout embryonic and larval development before initiating apoptosis around the start of metamorphosis. The innervation of embryonic skin …

Apoaequorin Differentially Modulates Fear Conditioning In Adult And Aged Rats, Vanessa Ehlers

Theses and Dissertations

Normal aging is associated with a number of changes in behavioral and cellular function, and is often linked to increased susceptibility to cognitive impairment. The hippocampus has been widely implicated in learning and memory, and many forms of learning that are hippocampus-dependent (e.g. trace fear conditioning) are impaired in aged animals. A proposed contributor to aging-related cognitive impairment is aging-related calcium (Ca2+) dysregulation. This dysregulation is thought to result from changes in specific Ca2+-regulatory mechanisms, including abnormal Ca2+ ion channel activity or expression, as well as reduced Ca2+-binding protein (CaBP) expression, which is associated with cognitive and synaptic impairment. Previous …

The Effects Of Exercise Pattern And Intensity On The Expression Of Flk-1 And Flt-1 Receptors In The Hippocampus And Cerebellum, Morgan E. Stevenson

Theses and Dissertations

Aerobic exercise benefits the body and brain. In the brain, these benefits include neuroprotection and improved cognition. These exercise-induced changes are attributed in part to angiogenesis: the growth of new capillaries from preexisting vessels. One critical factor involved in the regulation of angiogenesis is VEGF and its receptors Flk-1 and Flt-1. Although exercise is generally found to be beneficial, there are wide variations in the exercise regimens used across experiments. This study standardized some of these variations. In this study, rats were either assigned to a voluntary wheel running or a forced wheel running exercise condition. Within each condition, animals …

Neural Circuitry Underlying The Intrusion Of Task-Irrelevant Threat Into Working Memory In Anxiety, Daniel Stout

Theses and Dissertations

Dispositional anxiety is an important risk factor for the development of anxiety and other psychological disorders. Symptoms commonly expressed by highly anxious individuals include intrusive memories, uncertainty, and worry — all occurring in the absence of immediate threat. This raises the possibility that anxious individuals have difficulty governing threat’s access to working memory, the mental workspace where goal-related information is actively retained for guiding on-going behavior. Using functional magnetic resonance imaging (fMRI) while 81 subjects completed a well-validated working memory task, I show that threat-related and neutral distracters unnecessarily gain access to working memory, as evidenced by increased neural activity …

The Mechanisms Underlying Cocaine-Induced Overexpression Of Basic Fibroblast Growth Factor (Bfgf, Fgf2), An Effect Reversed By Extinction, Madalyn Hafenbreidel

Theses and Dissertations

Drug addiction is characterized by compulsive drug use and chronic relapse despite negative consequences. Drug-induced structural and functional changes in the brain are thought to underlie these characteristics. One mechanism that may mediate these characteristics are growth factors, such as basic fibroblast growth factor (bFGF or FGF2), as they are necessary for cellular growth, survival, differentiation, and have roles in memory, mood, and anxiety disorders. bFGF mRNA and protein expression is increased following stimulant administration and is necessary for stimulant-induced changes in dendrites and behavioral sensitization. Moreover, addiction is maintained by cues associated with the drug, as they can can …

Spectral Domain-Optical Coherence Tomography For The Assessment Of Cerebrovascular Plasticity, Jacob James Michael Kay

Theses and Dissertations

Vascular pathologies represent the leading causes of mortality worldwide, accounting for 31% of all deaths in 2012. Cerebral hypoxia is a condition that often manifests as a result of these medical conditions. Remarkably, the nervous system has evolved mechanisms to compensate for oxygen deprivation. The dilation of existing vessels and the growth of new blood vessels are two prominent physiological responses to hypoxia, both of which play a critical role in maintaining cerebral homeostasis. More recently, exercise has been shown to induce a mild state of hypoxia in the brain, leading to several robust morphological changes within the cerebrovascular system …

Neural Plasticity Of Extinction: Relations With Anxiety And Extinction Retention, Emily Louise Belleau

Theses and Dissertations

ABSTRACT

NEURAL PLASTICITY OF EXTINCTION LEARNING: RELATIONS WITH ANXIETY AND EXTINCTION RETENTION

by

Emily L. Belleau

The University of Wisconsin-Milwaukee, 2016

Under the Supervision of Associate Professor Christine Larson

Anxiety is a significant public health problem characterized by substantial psychological, physical, and economic burden. A key feature of anxiety is the inability to regulate fear. Aberrant extinction of conditioned fear is one prominent model of the etiology of anxiety disorders. Previous studies have shown that the neural circuitry underlying anxiety pathology overlaps with that mediating fear extinction learning. Recently, more precise pathways supporting the expression (CMA-aMCC) and inhibition (BLA-vmPFC) of …