Neuroscience and Neurobiology Commons^™

Mapping The Functional Organization Of Human Frontoparietal Cortex With Fmri, Geetika Gupta

Electronic Thesis and Dissertation Repository

Higher-order cognitive functions, such as working memory, attention, and decision making, depend strongly on the functional integrity of frontal and parietal cortices. However, the internal workings of the frontoparietal network (FPN) are not well understood. A major contributor to this knowledge gap is our limited understanding of the intrinsic functional organization of the FPN. In order to address this gap, we examine task-dependent reconfigurations of functional connectivity (FC) within the FPN. We analyzed fMRI task-state data from 924 individuals from the Human Connectome Project Young Adult study. Our results show that FC within the FPN is highly stable across time …

The Functional And Structural Consequences Of Aberrant Microglial Activity In Major Depressive Disorder, Jasmine D. Cakmak

Electronic Thesis and Dissertation Repository

Major depressive disorder (MDD) is a highly debilitating neuropsychiatric illness which has been linked with increases in both peripheral and central inflammation, as well as with changes in connectivity. Although countless studies have investigated these two topics, the relationship between neuroinflammation and functional/structural connectivity has not been explored. Using [¹⁸F]FEPPA PET imaging, we measured translocator protein-related (TSPO) microglial activity in the subgenual anterior cingulate cortex (sgACC) and insula and confirmed significantly increased [¹⁸F]FEPPA uptake in depressed patients (N=12) compared to healthy controls (N=23). Using a seed-based ROI analysis of fMRI data, we found that patients show …

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 …

A Role For The Somatosensory System In Motor Learning By Observing, Heather R. Mcgregor

Electronic Thesis and Dissertation Repository

An influential idea in neuroscience is that action observation activates an observer’s sensory-motor system. This idea has recently been extended to motor learning; observing another individual undergoing motor learning can promote sensory-motor plasticity as well as behavioural changes in both the motor and somatosensory domains. While previous research has suggested a role for the motor system in motor learning by observing, this thesis presents a series of experiments testing the hypothesis that the somatosensory system is also involved in motor learning by observing.

The experiments included in this thesis used force field (FF) adaptation as a model of motor learning, …

Movie-Driven Fmri Reveals Network Asynchrony And Connectivity Alterations In Temporal Lobe Epilepsy, Alenka Bullen

Electronic Thesis and Dissertation Repository

Mesial temporal lobe epilepsy (TLE) is the most common form of focal epilepsy and is often resistant to medication. Recent studies have noted brain-wide disruptions to several neural networks in so-called “focal” epilepsy, notably TLE, leading to it being recognized as a network disease. We aimed to assess the integrity of functional networks while they were simultaneously activated in an ecologically valid manner, using an actively engaging, richly stimulating audio-visual film clip. This stimulus elicits widespread, dynamic patterns of time-locked brain activity, measurable using functional magnetic resonance imaging. Thirteen persons with drug-resistant TLE (persons with epilepsy; PWE) and 10 demographically …

Functional Connectivity In The Motor Network Largely Matures Before Motor Function, Jordynne L V Ropat

Electronic Thesis and Dissertation Repository

The brain changes in many ways in the first year. It is not known which of these changes are most critical for the development of cognitive functions. According to the Interactive Specialization Theory, developments in behaviour result from changes in brain connectivity. We tested this using functional connectivity magnetic resonance imaging (fcMRI) of the motor system. fcMRI was acquired at three and nine months – two time-points between which motor behaviour develops enormously. Infants were additionally compared with adults. Subjects were scanned with a 3T MRI scanner, yielding BOLD signal time-courses that were correlated with one another. Our results do …

Optimizing The Analysis Of Electroencephalographic Data By Dynamic Graphs, Mehrsasadat Golestaneh

Electronic Thesis and Dissertation Repository

The brain’s underlying functional connectivity has been recently studied using tools offered by graph theory and network theory. Although the primary research focus in this area has so far been mostly on static graphs, the complex and dynamic nature of the brain’s underlying mechanism has initiated the usage of dynamic graphs, providing groundwork for time sensi- tive and finer investigations. Studying the topological reconfiguration of these dynamic graphs is done by exploiting a pool of graph metrics, which describe the network’s characteristics at different scales. However, considering the vast amount of data generated by neuroimaging tools, heavy computation load and …

The Hippocampus Participates In A Pharmacological Rat Model Of Absence Seizures, Justin Andrew Arcaro

Electronic Thesis and Dissertation Repository

The thalamocortical network is responsible for the generation of spike-and-wave discharges (SWDs) in absence epilepsy. Recent studies suggest a potential involvement of the hippocampus, which may explain the variability in the extent of cognitive deficits among patients with absence epilepsy. I hypothesize that the hippocampus may become entrained in spike-and-wave discharges following thalamocortical activation. The gamma-butyrolactone (GBL) rat model of absence seizures was used in this thesis. Following GBL injection, SWDs of 4 to 6 Hz developed in the spontaneous local field potentials (LFPs) recorded by depth electrodes in the thalamus, neocortex and hippocampus. Synchronization of hippocampal, thalamic and neocortical …

Brain Connectivity Studied By Fmri: Homologous Network Organization In The Rat, Monkey, And Human, R. Matthew Hutchison

Electronic Thesis and Dissertation Repository

The mammalian brain is composed of functional networks operating at different spatial and temporal scales — characterized by patterns of interconnections linking sensory, motor, and cognitive systems. Assessment of brain connectivity has revealed that the structure and dynamics of large-scale network organization are altered in multiple disease states suggesting their use as diagnostic or prognostic indicators. Further investigation into the underlying mechanisms, organization, and alteration of large-scale brain networks requires homologous animal models that would allow neurophysiological recordings and experimental manipulations. My current dissertation presents a comprehensive assessment and comparison of rat, macaque, and human brain networks based on evaluation …

Toward A Functional Characterization Of Cognitive Control Networks, Frederick Ezekiel

Electronic Thesis and Dissertation Repository

Cognitive control is an executive process that has been associated with a distributed set of cortical regions. These distributed regions appear to cluster into distinct networks with dissociable functions. In this study, independent component analysis was used as a tool to investigate functional connectivity in event-related fMRI data. Extracted networks of interest were functionally characterized using a hybrid task that independently probed moment-to-moment adjustments in control, and stable task-set maintenance. A cinguloinsular network was implicated in the processing of moment-to-moment adjustments in control based on its activation patterns during this task. Subsequently, functional connectivity between two networks previously implicated in …