Life Sciences Commons^™

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 …

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 …

Chemosensory Processing By The Mediodorsal Thalamus., Kelly Fredericksen

Electronic Theses and Dissertations

The mediodorsal thalamus (MD) is thought to be key component of the network that processes chemosensory information to guide our consummatory choices. Previous studies show that the mediodorsal thalamus receives projections from both the piriform cortex (PC) and gustatory cortex (GC), suggesting that it may process chemosensory information from both areas. Although the mediodorsal thalamus has been shown to respond to odors detected by sniffing, it remains unknown how its neurons represent experienced odors, tastes, and odor-taste mixtures originating from the mouth. Importantly, humans and animals with mediodorsal thalamic lesions do not suffer from anosmia, but experience deficits in odor …

Gabaergic Interneurons And Prenatal Ethanol Exposure: From Development To Aging, Adelaide R. Tousley

Dartmouth College Ph.D Dissertations

Fetal Alcohol Spectrum Disorders are the most common non-genetic cause of neurodevelopmental disability worldwide. Individuals with Fetal Alcohol Spectrum Disorder experience clinical symptoms including differences in physical, cognitive and behavioral development beginning in early childhood, but continue to face challenges into adulthood. There is a critical need to examine the effects of prenatal ethanol exposure across early development, and to establish how the developmental effects of prenatal ethanol exposure may or may not progress in aging individuals. To contribute to these two areas, I asked how a binge-type prenatal ethanol exposure might affect: (1) early postnatal development of striatal neurons …

Peripheral Modulation Of Cardiac Contractions In The American Lobster, Homarus Americanus, By The Peptide Myosuppressin Is Mediated By Effects On The Cardiac Muscle Itself, Isabel Stella Petropoulos

Honors Projects

A substantial factor for behavioral flexibility is modulation — largely via neuropeptides — which occurs at multiple sites including neurons, muscles, and the neuromuscular junction (NMJ). Complex modulation distributed across multiple sites provides an interesting question: does modulation at multiple locations lead to greater dynamics than one receptor site alone? The cardiac neuromuscular system of the American lobster (Homarus americanus), driven by a central pattern generator called the cardiac ganglion (CG), is a model system for peptide modulation. The peptide myosuppressin (pQDLDHVFLRFamide) has been shown in the whole heart to decrease contraction frequency, largely due to its effects on …

Multimodal Neuron Classification Based On Morphology And Electrophysiology, Aqib Ahmad

Graduate Theses, Dissertations, and Problem Reports

Categorizing neurons into different types to understand neural circuits and ultimately brain function is a major challenge in neuroscience. While electrical properties are critical in defining a neuron, its morphology is equally important. Advancements in single-cell analysis methods have allowed neuroscientists to simultaneously capture multiple data modalities from a neuron. We propose a method to classify neurons using both morphological structure and electrophysiology. Current approaches are based on a limited analysis of morphological features. We propose to use a new graph neural network to learn representations that more comprehensively account for the complexity of the shape of neuronal structures. In …

Sensorimotor Content Of Multi-Unit Activity In The Paramedian Lobule Of The Cerebellum, Esma Cetinkaya

Dissertations

Based on Center for Disease Control and Prevention report 2016, around 39.5 million people in the United States suffer from motor disabilities. These disabilities are due to traumatic conditions like traumatic brain injury (TBI), neurological diseases such as amyotrophic lateral sclerosis (ALS), or congenital conditions. One of the approaches for restoring the lost motor function is to extract the volitional information from the central nervous system (CNS) and control a mechanical device that can replace the function of a paralyzed limb through systems called Brain-Computer Interfaces (BCI).

One of the major challenges being faced in BCIs and also in general …

Spatial Representation In Postrhinal Cortex, Patrick Lachance

Dartmouth College Ph.D Dissertations

Animals rely on a variety of internal and external cues to orient themselves when navigating their environments and determining their current spatial context. Information regarding these cues enters the brain from the navigator’s first-person perspective. Information of this type is considered to be egocentric, or self-centered. However, decades of behavioral, electrophysiological, and imaging research suggest that the brain contains a rich collection of spatial representations that are unrestricted by the animal’s first-person perspective, and instead are defined relative to the surrounding environment. These representations are considered allocentric, or world-centered. Despite an abundance of promising modeling work, the specific mechanisms by …

Characterizing And Investigating The Electrophysiological Properties Of The Plastic Cricket Auditory System In Response To Cooling, Hannah Tess Scotch

Honors Projects

The auditory system of the Mediterranean field cricket (Gryllus bimaculatus) is capable of profound compensatory plasticity. Following deafferentation due to the loss of an auditory organ, the dendrites of intermediate auditory neuron Ascending Neuron 2 (AN-2) grow across the midline and functionally connect to contralateral afferents. The loss of the auditory organ can be mimicked with reversible cold-deactivation, in which cooled Peltier elements silence the auditory organ and its afferents. Though this would presumably prevent AN-2 from firing, cooling instead induces a novel firing pattern called DOPE (delayed-onset, prolonged-excitation). In this study, intracellular physiological recordings were completed before, …

Estrogen Modulation Of Vta Dopamine Neuron Physiology And Behavioral Responsivity To Variable Social Stressors, Mary R. Shanley

Dissertations, Theses, and Capstone Projects

The behavioral output of different animals, or even the same animal in different contexts, is remarkably variable in response to the same external stimulus. This behavioral diversity is due to the complex integration of external and internal stimuli, through both neuronal and hormonal signals that selects the best behavioral response. By their nature as long-distance signaling molecules, hormones play a critical role in communicating information about internal states across the organism. Many hormones produced in the periphery target the central nervous system to modulate animal behavior, selecting for behaviors that are appropriate over behaviors that are maladaptive in that specific …

Towards Understanding The Role Of Central Processing In Release From Masking, Nima Alamatsaz

Dissertations

People with normal hearing have the ability to listen to a desired target sound while filtering out unwanted sounds in the background. However, most patients with hearing impairment struggle in noisy environments, a perceptual deficit which current hearing aids and cochlear implants cannot resolve. Even though peripheral dysfunction of the ears undoubtedly contribute to this deficit, surmounting evidence has implicated central processing in the inability to detect sounds in background noise. Therefore, it is essential to better understand the underlying neural mechanisms by which target sounds are dissociated from competing maskers. This research focuses on two phenomena that help suppress …

Effects Of The Antidepressant Drug Vortioxetine On Ventral Pallidal Neuronal Activity, Respiration, And Heart Rate In The Rat, Piper Rogers

Theses and Dissertations

Major Depressive Disorder (MDD) is a mental illness that affects millions of people worldwide. People diagnosed with MDD are often prescribed antidepressant drugs. Most antidepressants increase levels of serotonin (5-hydroxytryptamine, 5-HT) in the synapses between neurons. Selective-serotonin reuptake inhibitors (SSRIs), one class of antidepressants, do this by inhibiting the reuptake of serotonin released into the synapse. Serotonin neurons from the brainstem raphe nuclei affect a wide range of areas throughout the brain. Among these areas is the ventral pallidum (VP), located in the basal forebrain. Citalopram, an SSRI, has been found to increase the firing rate of action potentials of …

Network And Cellular Effects Of The Mu Opioid Receptor In Cortical Interneurons, Adrian Dutkiewicz

Graduate College Dissertations and Theses

The µ opioid receptor (µOR) exerts a powerful excitatory effect in cortical circuits and cultured neurons by promoting glutamatergic activity after binding endogenous or exogenous opioids. While most research indicates that the receptor does this by decreasing activity or output of GABAergic interneurons that inhibit glutamate-releasing Pyramidal Neurons, other experiments suggest that the µOR directly upregulates excitatory Pyramidal Neurons instead. Thus, the cellular target of cortical opioid agonists remains unclear, and the µOR’s net excitatory mechanisms are not fully understood. Consequently, utilizing electrophysiology to detect µOR responses to the specific agonist [D-Ala2, N-Me-Phe4, Gly5-ol]-Enkephalin (DAMGO) has yielded incomplete information on …

The Effects Of Interneuron Progenitor Cell Transplantation On Network Dynamics In An Animal Model Of Mesial Temporal Lobe Epilepsy, Willie Curry

Graduate College Dissertations and Theses

Epilepsy is associated with a very high incidence of cognitive and behavioral comorbidities that are detrimental to overall quality of life. Current treatments for epilepsy,namely anticonvulsant pharmacological agents, generally increase the amount of inhibitory drive in order to counteract the hyperexcitability observed in the disorder. However, administration of these agents, while effective for 70% of epilepsy sufferers, leave a residual 30% of patients who don’t become seizure-free. The concomitant adverse side effects of anticonvulsants - these can paradoxically include increased cognitive "fog" or confusion, automatisms, and even increased number of seizures - are a great additional concern, as is the …

Muscarinic Excitation Of Dopamine Neurons In The Ventral Tegmental Area Via Activation Of A Trpc-Like Cation Conductance, Yu Tzu Chen

Theses and Dissertations

Dopaminergic (DA) neurons in the ventral tegmental area (VTA) play a crucial role in reward and motivational behaviors, including the development of drug addictions. VTA DA neurons receive excitatory cholinergic inputs from the mesopontine tegmentum. Blockage of the M5 muscarinic receptor in DA neurons has been shown to attenuate drug-induced DA release and abuse-related behaviors, but the molecular mechanism is unknown. In this study, experiments were designed to identify the electrophysiological effects of muscarinic agonism in the modulation of action potential kinetics and firing patterns in VTA DA neurons of mice. Pharmacology of the muscarinic receptor-evoked current was also characterized. …

Manipulating The Perineuronal Net In The Deep Cerebellar Nucleus, Deidre E. O'Dell

Graduate Theses, Dissertations, and Problem Reports

Perineuronal nets (PNN) are a type of specialized extracellular matrix in the central nervous system. The PNN forms during postnatal development but the ontogeny of the PNN has yet to be elucidated. Studying the PNN in the rat brain may allow us to further understand the PNN’s role in development, learning, and memory. The PNN is fully developed in the deep cerebellar nuclei (DCN) of rats by post-natal day 18. By using enzymatic digestion of the PNN with chondroitinase ABC (ChABC), we studied how digestion of the PNN affects cerebellar-dependent eyeblink conditioning (EBC) and performed electrophysiological recordings from DCN neurons. …

Optogenetic Interrogation Of Hippocampal Circuit Stabilization, Laurel Watkins De Jong

Theses and Dissertations

Understanding the response of excitatory and inhibitory populations to varying input is vital to understanding how a brain region transforms information. Optogenetics - the combined use of optics and genetics to control the activity of proteins, provides neuroscientists with a tool to interrogate neuronal circuits with high spatio-temporal resolution and targeted cell specificity. This thesis examines the effects of optogenetic manipulations on hippocampal circuit responses. The hippocampus is a structure required for the formation and retention of episodic memories and is comprised of anatomically distinct subregions including cornu ammonis 3 (CA3) and cornu ammonis 1 (CA1). Both regions, despite differences …

Divergence In Neuronal Calcium Dysregulation In Brain Aging And Animal Models Of Ad, Adam Ghoweri

Theses and Dissertations--Pharmacology and Nutritional Sciences

Neuronal calcium dysregulation first garnered attention during the mid-1980’s as a key factor in brain aging, which led to the formulation of the Ca²⁺ hypothesis of brain aging and dementia. Indeed, many Ca²⁺-dependent cellular processes that change with age, including an increase in the afterhyperpolarization, a decrease in long-term potentiation, an increased susceptibility to long-term depression, and a reduction in short-term synaptic plasticity, have been identified. It was later determined that increased intracellular Ca²⁺ with age was due to increased Ca²⁺ channel density, elevated release from intracellular Ca²⁺ stores, and decreased Ca²⁺ buffering …

Responses Of Central Pattern Generators In The American Lobster Stns To Multiple Members Of A Novel Neuropeptide Family, Benjamin Harley Wong

Honors Projects

Neuropeptides are important modulators of neural activity, allowing neural networks, such as the central pattern generators (CPGs) that control rhythmic movements, to alter their output and thus generate behavioral flexibility. Isoforms of a neuropeptide family vary in physical structure, allowing potentially distinct functional neuromodulatory effects on CPG systems. While some familial neuropeptide isoforms can differentially affect a system, others in the same family may elicit indistinguishable effects. Here, we examined the effects elicited by members of a novel family of six peptide hormone isoforms (GSEFLamides: I-, M-, AL-, AM-, AV-, and VM-GSEFLamide) on the pyloric filter and gastric mill CPGs …

The Brain's Large-Scale Electrophysiological Signals : Fundamental Attributes And Neurosurgical Applications, Mohammad Amin N/A Nourmohammadi

Legacy Theses & Dissertations (2009 - 2024)

Brain’s electrophysiological signals are most certainly the ultimate source for studying the sophisticated neural network inside our cranium. The unparalleled complexity of these biosignalsis the quintessential manifestation of their underlying complicated neurophysiological processes. Studying brain signals on the cellular level provides valuable information regarding the brain’s electrophysiology on the small-scale. However, it is the remarkable network in the large-scale that gives rise to the brain’s extraordinary attributes and exceptional capabilities—perception, cognition, computation, and consciousness are all the emergent byproducts of the dynamic neuronal interactions on the network level. In this sense, the large-scale electrophysiological signals, recorded from the surface of …

Divalent Metal Cation Entry And Cytotoxicity In Jurkat T Cells: Role Of Trpm7 Channels, Alayna N. Mellott

Browse all Theses and Dissertations

Humans are exposed daily to a variety of metals that can be harmful to our immune system. Although certain divalent metal cations are essential for numerous cellular functions and are critical trace elements in humans, the uptake mechanisms of these ions remain mostly unknown. Transient receptor potential melastatin 7 (TRPM7), which is expressed in a variety of human cell types, including lymphocytes and macrophages, conducts many divalent metal cations. TRPM7 channels are largely inactive under normal physiological conditions due to cytoplasmic magnesium acting as a channel inhibitor. Magnesium is a cofactor for many biochemical reactions. Low serum levels of magnesium, …

Understanding Object Motion Encoding In The Mammalian Retina., Victor Julian Depiero

Electronic Theses and Dissertations

Phototransduction, transmission of visual information down the optic nerve incurs delays on the order of 50 – 100ms. This implies that the neuronal representation of a moving object should lag behind the object’s actual position. However, studies have demonstrated that the visual system compensates for neuronal delays using a predictive mechanism called phase advancing, which shifts the population response toward the leading edge of a moving object’s retinal image. To understand how this compensation is achieved in the retina, I investigated cellular and synaptic mechanisms that drive phase advancing. I used three approaches, each testing phase advancing at a …

Coupled Correlates Of Attention And Consciousness, Ravi Varkki Chacko

McKelvey School of Engineering Theses & Dissertations

Introduction: Brain Computer Interfaces (BCIs) have been shown to restore lost motor function that occurs in stroke using electrophysiological signals. However, little evidence exists for the use of BCIs to restore non-motor stroke deficits, such as the attention deficits seen in hemineglect. Attention is a cognitive function that selects objects or ideas for further neural processing, presumably to facilitate optimal behavior. Developing BCIs for attention is different from developing motor BCIs because attention networks in the brain are more distributed and associative than motor networks. For example, hemineglect patients have reduced levels of arousal, which exacerbates their attentional deficits. More …

Electrophysiological Mechanisms For Preparing Control In Time, Jacqueline Rosemary Janowich

Psychology ETDs

Cognitive control is critical in guiding goal-directed behavior, preparing neural resources and adapting processing to promote optimal action in a given environment. According to the Dual Mechanisms of Control theory (Braver, 2012), control can be dichotomized into proactive and reactive modes of control, utilized reciprocally in ahead-of-time preparation versus last-minute, stimulus-evoked reaction. Although a substantial body of work has tested differences between proactive control and reactive control, the underlying assumption of proactive control as a unitary process has not been systematically investigated. Very little is known as to how or when proactive control is initiated, sustained, or implemented.

As time …

The Effects Of A Ketone Body On Synaptic Transmission, Alexandra Elizabeth Stanback

Theses and Dissertations--Biology

The ketogenic diet is commonly used to control epilepsy, especially in cases when medications cannot. The diet typically consists of high fat, low carb, and adequate protein and produces a metabolite called acetoacetate. Seizure activity is characterized by glutamate excitotoxicity and therefore glutamate regulation is a point of research for control of these disorders. Acetoacetate is heavily implicated as the primary molecule responsible for decreasing glutamate in the synapse; it is believed that acetoacetate interferes with the transport of glutamate into the synaptic vesicles. The effects on synaptic transmission at glutamatergic synapses was studied in relation to the ketogenic diet …

Shining Light On An Amygdala -- Brainstem Connection Important For Attention Processing, Jose Carlos Cano

Open Access Theses & Dissertations

We are continuously being exposed to an exorbitant amount of sensory information, which should result overwhelming. However, the nervous system operates several intrinsic sensory filtering mechanisms that allow us to cope with such sensory cluttering and shape appropriate behavior. Sensorimotor gating is a pre-attentive neuronal filtering mechanism that gates superfluous sensory information, and orients attentional resources towards salient information processing. Its relevance becomes in individuals suffering from schizophrenia and several otherwise unrelated neuropsychiatric disorders where sensorimotor gating is impaired. To understand the neural impaired mechanisms, extensive research studies have focused on first identifying the neural substrates underlying sensorimotor gating. This …

Cannabinoid Transmission In The Basolateral Amygdala Modulates Prefrontal Cortex And Ventral Hippocampal Activity, Brian J. Pereira

Electronic Thesis and Dissertation Repository

The cannabinoid system is important for maintaining neuron-to-neuron communication within the mammalian brain. One of the most commonly used substances to alter the cannabinoid system is cannabis. Individuals who are exposed to cannabis report having dissociable effects; both positive and negative. High amounts of THC have been commonly associated with the negative effects of cannabis, whereas CBD can be used to counter these. Pre-clinical evidence suggests that the combination of the two compounds can produce a therapeutic benefit for individuals who are susceptible to the effects of THC. The present study investigates whether the combination of THC+CBD can prevent electrophysiological …

Characterizing The Cortical Contributions To Working Memory-Guided Obstacle Locomotion, Carmen Wong

Electronic Thesis and Dissertation Repository

While walking in complex environments, the ability to acquire information about objects in our surroundings is essential for successful obstacle negotiation. Furthermore, the ease with which most animals can traverse cluttered terrain while grazing, exploring, or hunting is facilitated by the capacity to store obstacle information in working memory (WM). However, the underlying neural substrates supporting such complex behaviours are poorly understood. Therefore, the goal of this thesis is to examine the neural underpinnings of WM-guided obstacle negotiation in the walking cat.

Obstacle locomotion was studied in two main paradigms, characterized by whether obstacle presence was detected via vision or …

Characterizing The Cognitive And Emotional Effects Of Delta-9-Tetrahydrocannabinol In Distinct Hippocampal Sub-Regions, Dinat Khan

Electronic Thesis and Dissertation Repository

The objective of this study is to determine the potential differential effects of THC in the DH or VH sub-regions, as well as the upstream effects on PFC neuronal activity and oscillations. Rodents used for electrophysiology were infused with THC or vehicle in the DH or VH regions, combined with PFC recordings. Additionally, a battery of behavioural paradigms was performed. Deficits in short-term memory when THC was infused into both regions was observed, however working memory was impaired with VH infusions only. This could be due to THC-induced dysregulation in the PFC, as beta oscillations were significantly decreased selectively in …

Population Codes And Their Correlates In Decision Making, Neda Shahidi

Dissertations & Theses (Open Access)

This dissertation was organized in two parts: in part 1, we discussed Neural Correlates of Perceptual Accuracy” and in part 2 we discussed “Strategy encoding in Prefrontal Cortex”.

Abstract of part 1_The accurate transmission of electrical signals within neocortex is central to sensory perception and cognition. Theoretical studies have long proposed that the temporal coordination of cortical spiking activity controls signal transmission and cognitive function. In reality, whether and how the precise temporal coordination in neuronal populations during wakefulness influences perception remains a mystery. Here, we simultaneously recorded populations of neurons in early and mid-level visual cortex (areas V1 …