Computational Neuroscience Commons^™

Mapping And Modeling Threat-Evoked Brain States After Early Life Adversity, Taylor W. Uselman

Biomedical Sciences ETDs

Early life adversity (ELA) increases lifelong neuropsychiatric vulnerability. Yet how ELA reorganizes brain-wide activity and circuit coordination across later experience remains unclear. This dissertation tests the hypothesis that ELA alters adult brain-wide activity and responses to threat through disrupted coordination among neural systems that regulate emotional experience, including prefrontal-limbic and monoaminergic systems. Longitudinal manganese-enhanced MRI of adult mice exposed to standard or fragmented early care, combined with computational processing and statistical modeling, quantified brain states before, during, and long after innate predator threat. These studies established that acute threat evokes large-scale, distributed brain activity that evolves over time. ELA potentiates …

A Predictive Coding Account Of Spatial Working Memory Following Prophylactic Levetiracetam Administration Prior To Traumatic Brain Injury, Omeima Mutwali

Dissertations, Theses, and Capstone Projects

Traumatic brain injury (TBI) symptom prevention and remediation is an important area of research that would benefit vulnerable groups, including active-duty and veteran soldiers. These patients can sustain penetrative forces in fields of combat or in training, which result in focal lesions that trigger inflammatory and degenerative processes in the brain. Both primary and secondary injuries are associated with changes to cognition, behavior and affective state. This disease poses increased risk of epileptogenesis, as well. Given these outcomes, prior research has evaluated levetiracetam (LEV) as a prophylactic treatment for seizures, cognitive deficits and negative emotionality. LEV acts as a presynaptic …

Vergence Task-Based Neural Pathways With Binocularly Normal Vision And Comorbid Persistent Post-Concussive Symptoms -Convergence Insufficiency, Ayushi Sangoi

Dissertations

Binocular dysfunctions are more prevalent in the persistent post-concussive symptoms (PPCS) population than in the general population. The most prevalent binocular disorder is convergence insufficiency (CI), affecting 3-17% of the general population and up to 10 times as many people with PPCS. CI makes it difficult to fuse or maintain fusion on targets at near, and its symptoms include double or blurry vision and headaches when performing close-range tasks such as reading, which can exacerbate PPCS symptoms. Given controversy over the subjectivity and effectiveness of diagnostic tools and symptom surveys for both PPCS and CI, understanding why CI has high …

Transcranial Ac Modulation Of Cerebellar Nuclear Activity In Awake Animals, Nuran Kavakli

Dissertations

Entrainment of cerebellar nuclear (CN) cells via cerebellar transcranial alternating current stimulation (ctACS) has been reported in animals under ketamine/xylazine anesthesia. Our main objective was to demonstrate modulation of CN activity in unanesthetized, freely moving animals using ctACS. Multi-channel carbon-fiber electrodes were implanted into the interpositus nucleus for recording multi-unit (MU) activity, and thin-film electrodes were implanted subcutaneously over the posterior cerebellum for stimulation. A frequency-domain-based metric was developed to quantify modulation from MU signals. The results demonstrated modulation in a wide range of frequencies (4 Hz-300 Hz) as in anesthetized animals. In contrast, the amplitude of the peak in …

Delineating Differences In Firing Rate Estimates Of Healthy And Parkinsonian Single-Unit Basal Ganglia Recordings, Richard R. Foster, Cheng Ly

Biology and Medicine Through Mathematics Conference

No abstract provided.

Gap Junction Architecture And Synchronization Clusters In The Thalamic Reticular Nuclei, Alex Norwood

Biology and Medicine Through Mathematics Conference

No abstract provided.

Somatosensory Cortex Responses To Illusory Touch In A Visual-Tactile Integration Task, Aditi Surendra Pawar

Dissertations, Theses, and Capstone Projects

Perceptual illusions arising from multisensory integration reveal how the brain constructs subjective experience from sensory input, and provide a powerful means of allowing the investigation of neural processes that track perceptual interpretation rather than physical stimulation alone. While visual illusions induced by auditory or tactile stimuli have been fairly well studied, the neural mechanisms underlying visually-induced illusory touch remain unclear. This study investigated whether illusory tactile perception engages the somatosensory cortex in a manner similar to veridical touch. Twenty healthy adults participated in an event-related functional magnetic resonance imaging (fMRI) study while performing a tactile numerosity judgment task. Each trial …

How To Search For The Engram: Optogenetics And Network Dynamics, Claudia Garcia Jou

Dissertations, Theses, and Capstone Projects

Memories are thought to be encoded by ensembles of neurons called "engram cells", because their artificial activation with optogenetics leads to the behavioral expression of a memory. However, the physiological mechanisms that mediate this process remain unknown. In this thesis, I investigate how optogenetic stimulation of memory-tagged cells changes neuronal firing, spatial coding, and the geometry of neural manifolds. I used an active place avoidance task and a foraging task to label engram cells in the dorsal hippocampus with Channelrhodopsin2 (ChR2). I then recorded the hippocampal activity response to optogenetic stimulation in mice under anesthesia, head-fixed, or freely moving. I …

A Generalized Framework For The “Core” Thalamocortical Circuit Computation, Charles Liu

Dartmouth College Ph.D Dissertations

This thesis explores a biologically inspired computational framework based on a common excitatory-inhibitory circuit in the superficial layers of the cortex. By varying the strength of local feedback inhibition, this single circuit gives rise to distinct unsupervised learning behaviors: strong inhibition leads to clustering and hierarchical clustering, while weak inhibition produces principal component-like representations. From this principle, we develop three algorithms: Lateral Inhibition Clustering (LI-C), Lateral Inhibition Hierarchical Clustering (LI-HC), and Antipodal Iterative Mean Estimation (AIME).

LI-C performs clustering without requiring a predefined number of clusters, using a competitive learning rule to extract dominant patterns from data. LI-HC extends this …

Beyond The Square Pulse: Waveform Shape, Eeg Correlates, And The Pursuit Of Natural Sensation In Tens, Jason Whitson

Honors Undergraduate Theses

This study investigates the relationship between electrical stimulus characteristics of shape and charge on evoked sensations and electroencephalogram (EEG) data during multi-waveform transcutaneous electrical nerve stimulation (TENS) of the median nerve. Neuromodulation methods have traditionally had little control over the location and quality of their associated evoked sensation (e.g., electric, vibration, touch). This experiment utilized five unique stimulus waveforms during TENS stimulation. EEG data were collected concurrently to provide an introductory objective measure of the neural responses underlying these sensory changes. Eleven participants completed three tasks (thresholding, super-threshold stimulation, two-alternative forced choice) using a two-electrode TENS approach. Stimulus waveforms were …