Neuroscience and Neurobiology Commons^™

The Role Of Serotonin In The Estradiol-Dependent Selectivity Of Auditory Regions In Songbirds, Calista J. Henry

Electronic Thesis and Dissertation Repository

Breeding-typical levels of estradiol in songbirds has been shown to lead to selective auditory processing and induce a release of serotonin in auditory regions of the forebrain. These findings triggered the question of whether auditory discrimination is driven by estradiol directly, or by the associated release of serotonin. I treated non-breeding female white-throated sparrows (Zonotrichia albicollis) with either blank implants, 17β-estradiol, serotonin enhancer and blank implants, or serotonin antagonist and 17β-estradiol implants. Birds then heard male conspecific songs or control tones, and ZENK-immunoreactivity was quantified in the caudomedial nidopallium (NCM) and caudomedial mesopallium (CMM). While I did not …

Fraction Magnitude Understanding Across Learning Formats: An Fmri Study, Chloe A. Henry

Electronic Thesis and Dissertation Repository

Knowledge of fraction magnitudes are an important, but notoriously difficult mathematical concept to master. Behavioural work has begun to explore and compare the instructional tools used for fraction learning. However, how fraction instructional tools are processed in the brain remains an underexplored question. Therefore, in the present thesis, we used functional brain MRI methodology to examine the neural activity of adult participants while completing a fraction verification task using the number line and area model, two common methods of fraction learning. We found that both models commonly recruited fronto-parietal activity, the neural regions typically implicated in number processing. However, we …

Self-Supervised Pretraining And Transfer Learning On Fmri Data With Transformers, Sean Paulsen

Dartmouth College Ph.D Dissertations

Transfer learning is a machine learning technique founded on the idea that knowledge acquired by a model during “pretraining” on a source task can be transferred to the learning of a target task. Successful transfer learning can result in improved performance, faster convergence, and reduced demand for data. This technique is particularly desirable for the task of brain decoding in the domain of functional magnetic resonance imaging (fMRI), wherein even the most modern machine learning methods can struggle to decode labelled features of brain images. This challenge is due to the highly complex underlying signal, physical and neurological differences between …

The Directional Effect Of Target Position On Spatial Selective Auditory Attention, Heesung Park

Dissertations, 2020-current

Spatial selective auditory attention plays a crucial role in listening in a mixture of competing speech sounds. Previous neuroimaging studies have reported alpha band neural activity modulated by auditory attention, along with the alpha lateralization corresponding to attentional focus. A greater cortical representation of the attended speech envelope compared to the ignored speech envelope was also found, a phenomenon known as 'neural speech tracking’. However, little is known about the neural activities when attentional focus is directed on speech sounds from behind the listener, even though understanding speech from behind is a common and essential aspect of daily life. The …

Investigating The Roles Of The Dorsal And Ventral Striatum In Humor Comprehension And Appreciation Throughout Health, Aging, And Parkinson’S Disease, Maggie Prenger

Electronic Thesis and Dissertation Repository

Humor processing is thought to involve two distinct components. The first, humor comprehension, involves detecting and resolving incongruities that are present within a humorous stimulus. This is related to cognitive processes such as ambiguity resolution, response inhibition, working memory, and cognitive flexibility, functions that are mediated in part by the dorsal portion of the striatum (DS). Humor appreciation, on the other hand, refers to the subjective amusement and mirth that one experiences in response to a joke. This is related to reward processing, which implicates the ventral portion of the striatum (VS). Across three separate studies, we investigated the involvement …

Temporal Dynamics Of Natural Sound Categorization, Ali Tafakkor

Electronic Thesis and Dissertation Repository

While extensive research has elucidated the brain’s processing of semantics from speech sound waves and their mapping onto the auditory cortex, the temporal dynamics of how meaningful non-speech sounds are processed remain less examined. Understanding these dynamics is key to resolving the debate between cascaded and parallel hierarchical processing models, both plausible given the anatomical evidence. This study investigates how semantic category information from environmental sounds is processed in the temporal domain, using electroencephalography (EEG) collected from 25 participants and representational similarity analysis (RSA) along with models of acoustic and semantic information. We examined information extracted by the brain from …

Nmda Receptor Inhibition On Rodent Optimal Decision-Making In The Diminishing Returns Task, Seth Foust

Research Psychology Theses

There has been growing interest in using N-methyl-D-aspartate (NMDA) receptor antagonists as treatments for mood disorders, but there is still much to learn about their cognitive effects. Research shows NMDA receptors can affect decision-making, and the antagonist MK-801 has had varying effects in rodents. Specifically, some have reported impairments in working memory while foraging behaviors remained intact, while others have demonstrated changes in choice behavior related to delay or risk in behavior tasks. We investigated the role of NMDA receptors in the specific paradigm of optimal decision-making to further confirm MK-801’s effects and to explore whether inhibiting NMDA receptors alters …

Machine Learning Techniques For Improved Functional Brain Parcellation, Da Zhi

Electronic Thesis and Dissertation Repository

Brain parcellation studies are fundamental for neuroscience as they serve as a bridge between anatomy and function, helping researchers interpret how functions are distributed across different brain regions. However, two substantial challenges exist in current imaging-based brain parcellation studies: large variations in the functional organization across individuals and the intrinsic spatial dependence which causes nearby brain locations to have a similar function. This thesis presents a series of projects aimed to tackle these challenges from different perspectives by using advanced machine learning techniques.

To handle the challenge of individual variability in building precise individual parcellations, Chapter 3 introduces a novel …

Sex Differences In Mood And Anxiety-Related Outcomes In Response To Adolescent Nicotine Exposure, Tsun Hay Jason Ng

Electronic Thesis and Dissertation Repository

Nicotine dependence is causally linked to increased risk of mood/anxiety disorders in later life. Females are reported to experience a higher prevalence of anxiety/depressive disorders and challenges in smoking cessation therapies, suggesting a potential sex-specific response to nicotine exposure and mood/anxiety disorder risk. However, pre-clinical evidence of sex-specific responses to adolescent nicotine exposure is unclear. Thus, to determine any sex differences in anxiety/depressive-related outcomes, adolescent male and female Sprague Dawley rats received nicotine (0.4 mg/kg; 3x daily) or saline injections for 10 consecutive days, followed by behavioural testing, in-vivo electrophysiology and Western Blot analyses. Our results revealed that adolescent nicotine …

The Consolidation Of Memory Associations, Kyle A. Kainec

Doctoral Dissertations

Creating memories is a fundamental challenge for the human brain. To create memories, defining features of experiences must be stored distinguishably without forgetting other memories. Memory associations represent co-occurring features and defining features across experiences. Memory associations are represented as networks of information that are stored in the brain. New memory associations are encoded during experiences and can be used to update existing memory associations during offline intervals. However, the mechanisms that underlie how encoded memory associations are stored within existing networks during offline intervals remains unclear. The experiments in this dissertation address a significant theoretical gap in understanding the …

Noradrenergic Regulation Of Decision-Making In Female And Male Rats, Emma S. Dauster

Doctoral Dissertations

Decision-making is regulated by many associated brain regions, including the locus coeruleus (LC) and the prefrontal cortex (PFC). Disruptions in decision-making are a key feature of many disorders including attention-deficit/hyperactivity disorder which is disproportionately diagnosed in one sex over another for reasons unknown. LC or its primary neurotransmitter norepinephrine (NE) have been implicated in the etiology or treatment of disrupted decision-making. Understanding the relationship among LC, PFC, and decision-making across sexes may provide insight into the basic neurobiology of cognition and disorders that lead to disrupted decision making. There are sex differences in LC anatomy, however studies investigating sex differences …

The Modulation Of Lfp Characteristics In The Freely Moving Common Marmoset, William Jm Assis

Electronic Thesis and Dissertation Repository

The hippocampus is a neural structure critical for navigation. Neurons in this region, along with others, create a functional network which generates large-amplitude modulations known as local field potential (LFP) activity. Prior LFP research has predominantly used rodent animal models, however recent studies have shown that frequencies associated with navigation in other mammals do not correlate to those of the rodent. We hypothesized that LFP characteristics in the common marmoset are modulated by the speed and axis of travel of the animal. Two marmosets were placed in a free moving 3-dimensional environment where movement and neurological activity were recorded. Results …

Disentangling The Role Of Parvalbumin-Expressing Interneurons In Stimulus-Response Learning And Cognitive Flexibility, Harleen Rai

Electronic Thesis and Dissertation Repository

Habits enable animals to efficiently navigate their surroundings while tending to more cognitively demanding environmental factors. One mechanism underlying habit is known as stimulus-response (S-R) learning, which takes place in the dorsolateral striatum (DLS). However, there is limited knowledge regarding the complex striatal microcircuits involved in S-R learning and cognitive flexibility. Recently, attention has turned toward the GABAergic Parvalbumin-expressing (PV) interneurons that can modulate striatal outputs. Here, we utilized chemogenetic techniques and touchscreen cognitive assessments to analyze the influence of PV neurons on S-R learning in mice. When PV neurons were inhibited, during the acquisition of a S-R and cognitive …

The Importance Of Contrast Sensitivity, Color Vision, And Electrophysiological Testing In Clinical And Occupational Settings, Frances Silva

Theses & Dissertations

Visual acuity (VA) is universally accepted as the gold standard metric for ocular vision and function. Contrast sensitivity (CS), color vision, and electrophysiological testing for clinical and occupational settings are warranted despite being deemed ancillary and minimally utilized by clinicians. These assessments provide essential information to subjectively and objectively quantify and obtain optimal functional vision. They are useful for baseline data and monitoring hereditary and progressive ocular conditions and cognitive function. The studies in this dissertation highlight the value of contrast sensitivity, color vision, and cone specific electrophysiological testing, as well as the novel metrics obtained with potential practical clinical …

Investigation Of The Role Of The G-Protein-Coupled Estrogen Receptor In Memory Consolidation In Gonadectomized Male Mice, Gustavo Dalto Barroso Machado

Theses and Dissertations

Estrogens are cholesterol-derived hormones that play crucial physiological and pathological roles in both sexes and across the lifespan. Many research groups have replicated the beneficial roles of 17-beta-estradiol (E2), the most potent estrogen, in memory consolidation in the past decades, even though some mechanisms are still unclear. The rapid effects of E2 in memory formation are attributed to its binding to different estrogen receptors (ER), notably the intracellular receptors ER and ER, as well as the membrane ER called G protein-coupled estrogen receptor (GPER). Previous work from our laboratory demonstrated that acute post-training infusion of E2 into the dorsal hippocampus …

Novel Insights Into Oligodendrocyte Biology From Developmental Myelination Studies In Autophagy Deficient Mice And Analysis Of Oligodendrocyte Translatome Response To Contusive Spinal Cord Injury., Michael David Forston

Electronic Theses and Dissertations

Loss of myelin causes severe neurological disorders and functional deficits in white matter injuries (WMI) such as traumatic spinal cord injury (SCI). This dissertation is focused on autophagy in OL development and the OL translatome after SCI. Chapter I describes the history of myelin, OL development, and their involvement in neurodegenerative diseases and SCI. The proteostasis network, in particular autophagy, and its contributions to white matter pathology is discussed. It concludes examining advantages and disadvantages of unbiased omics tools, like RiboTag, to study transcriptional/translational landscapes after SCI. Chapter II focuses on autophagy in OPC/OL differentiation, survival, and proper myelination in …

Connectivity Of Amygdala Somatostatin-Expressing Neurons And Their Role In Taste-Guided Behavior., Jane Jeruto Bartonjo

Electronic Theses and Dissertations

The nucleus of solitary tract (NST) and parabrachial nucleus (PBN) represent the first and second central synapses of ascending gustatory information. Neural processing in these nuclei is influenced by descending input from forebrain regions such as the central nucleus of the amygdala (CeA). In mice, we have shown that somatostatin (Sst) expressing neurons of CeA that project to NST and PBN are largely distinct cell populations and optogenetic inhibition of the CeA/Sst-to-NST subpopulation increases the intake of high concentrations of quinine with no apparent effect on sucrose intake. Synaptic connectivity of these cells is needed to understand the possible mechanisms …

The Biological Bases Of Political Attachment: Neurobiological Correlates Of Ideology And Partisanship, Carisa Bergner

Theses and Dissertations

To fully understand the foundations of political attachments in an increasingly polarized environment, political scientists must reconcile traditional theories of political attitudes and behavior with insight gained from neurobiological approaches. The purpose of this research is to investigate the neurobiological correlates of strength of political ideology and partisanship, as well as the neurobiological correlates of ideological and partisan orientation. To do so, both structural and functional neuroimaging analyses were conducted on a diverse sample of patients at a Level 1 Trauma Center. Results indicate that strong ideological attachment is significantly associated with decreased volume in the left insula, though partisan …

Phenotyping Regression In A Female Mouse Model For Rett Syndrome Using Computational Neuroethology Tools, Michael J. Mykins

Doctoral Dissertations

Regression is defined as loss of acquired skills over time and is a key feature of many neurodevelopmental disorders such as Rett syndrome (RTT). RTT is caused by mutations in the X-linked gene Methyl CpG-Binding Protein 2 (MECP2) and is characterized by a period of typical development with subsequent regression of previously acquired motor and speech skills in girls. In human and animal models, it is clear syndromic phenotypes are dynamic over time but phenotyping regression over time in animal models has remained elusive. Lack of established timelines to study the molecular, cellular, and behavioral features of regression in female …

Identification Of Structural Brain Alterations In Adolescents With Depressive Symptomatology, J. Bashford‑Largo, R. James R. Blair, Karina S. Blair, Matthew Dobbertin, Ahria Dominguez, Melissa Hatch, Sahil Bajaj

Center for Brain, Biology, and Behavior: Faculty and Staff Publications

Introduction: Depressive symptoms can emerge as early as childhood and may lead to adverse situations in adulthood. Studies have examined structural brain alternations in individuals with depressive symptoms, but findings remain inconclusive. Furthermore, previous studies have focused on adults or used a categorical approach to assess depression. The current study looks to identify grey matter volumes (GMV) that predict depressive symptomatology across a clinically concerning sample of adolescents.

Methods: Structural MRI data were collected from 338 clinically concerning adolescents (mean age = 15.30 SD=2.07; mean IQ = 101.01 SD=12.43; 132 F). Depression symptoms were indexed via the Mood …