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Articles 1 - 5 of 5
Full-Text Articles in Medicine and Health Sciences
An Implementation Of Integrated Information Theory In Resting-State Fmri, Idan E. Nemirovsky
An Implementation Of Integrated Information Theory In Resting-State Fmri, Idan E. Nemirovsky
Electronic Thesis and Dissertation Repository
Integrated Information Theory (IIT) is a framework developed to explain consciousness, arguing that conscious systems consist of interacting elements that are integrated through their causal properties. In this study, we present the first application of IIT to functional magnetic resonance imaging (fMRI) data and investigate whether its principal metric, Phi, can meaningfully quantify resting-state cortical activity patterns. Data was acquired from 17 healthy subjects who underwent sedation with propofol, a short acting anesthetic. Using PyPhi, a software package developed for IIT, we thoroughly analyze how Phi varies across different networks and throughout sedation. Our findings indicate that variations in Phi …
Optimizing Preprocessing Of Fmri Data To Maximize Correspondence Of Functional Anatomy Across Individuals, Nargess Ghazaleh
Optimizing Preprocessing Of Fmri Data To Maximize Correspondence Of Functional Anatomy Across Individuals, Nargess Ghazaleh
Electronic Thesis and Dissertation Repository
In movie-activation fMRI, intersubject correlation (ISC) indicates a functional correspondence across viewers. Brains di↵er in shape; spatial normalization and smoothing enhance inter-subject functional overlap. We compare three normalization methods and six smoothing levels to discover which method yields the best functional overlap, indexed by ISC. This is key to optimizing data analysis in clinical studies using movie-activation fMRI in future. In a 3T scanner, 44 healthy subjects watched an 8-min movie. Both normalization and smoothing a↵ected the strength and extent of the ISC. ISC values were more robust for ANTs and DARTELthanforSPM12andwere(asymptotically)thestrongestat12mmsmoothing. When image data are preprocessed with high-dimensional volumetric …
Ultra-High Field Magnetic Resonance Imaging For Stereotactic Neurosurgery, Jonathan Lau
Ultra-High Field Magnetic Resonance Imaging For Stereotactic Neurosurgery, Jonathan Lau
Electronic Thesis and Dissertation Repository
Stereotactic neurosurgery is a subspecialty within neurosurgery concerned with accurate targeting of brain structures. Deep brain stimulation (DBS) is a specific type of stereotaxy in which electrodes are implanted in deep brain structures. It has proven therapeutic efficacy in Parkinson’s disease and Essential Tremor, but with an expanding number of indications under evaluation including Alzheimer’s disease, depression, epilepsy, and obesity, many more Canadians with chronic health conditions may benefit. Accurate surgical targeting is crucial with millimeter deviations resulting in unwanted side effects including muscle contractions, or worse, vessel injury. Lack of adequate visualization of surgical targets with conventional lower field …
Unravelling The Subfields Of The Hippocampal Head Using 7-Tesla Structural Mri, Jordan M. K. Dekraker
Unravelling The Subfields Of The Hippocampal Head Using 7-Tesla Structural Mri, Jordan M. K. Dekraker
Electronic Thesis and Dissertation Repository
Probing the functions of human hippocampal subfields is a promising area of research in cognitive neuroscience. However, defining subfield borders in Magnetic Resonance Imaging (MRI) is challenging. Here, we present a user-guided, semi-automated protocol for segmenting hippocampal subfields on T2-weighted images obtained with 7-Tesla MRI. The protocol takes advantage of extant knowledge about regularities in hippocampal morphology and ontogeny that have not been systematically considered in prior related work. An image feature known as the hippocampal ‘dark band’ facilitates tracking of subfield continuities, allowing for unfolding and segmentation of convoluted hippocampal tissue. Initial results suggest that this protocol offers sufficient …
A Model Of Intracellular Θ Phase Precession Dependent On Intrinsic Subthreshold Membrane Currents., L Stan Leung
A Model Of Intracellular Θ Phase Precession Dependent On Intrinsic Subthreshold Membrane Currents., L Stan Leung
Physiology and Pharmacology Publications
A hippocampal place cell fires at an increasingly earlier phase in relation to the extracellular theta rhythm as a rodent moves through the place field. The present report presents a compartment model of a CA1 pyramidal cell that explains the increase in amplitude and the phase precession of intracellular theta oscillations, with the assumption that the cell receives an asymmetric ramp depolarization (<10 >mV) in the place field and rhythmic inhibitory and/or excitatory synaptic driving. Intracellular subthreshold membrane potential oscillations (MPOs) increase in amplitude and frequency, and show phase precession within the place field. Theta phase precession and MPO power …