• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 121
  • 32
  • 28
  • 10
  • 7
  • 6
  • 4
  • 3
  • 3
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 262
  • 262
  • 262
  • 262
  • 64
  • 46
  • 46
  • 44
  • 44
  • 44
  • 43
  • 42
  • 39
  • 35
  • 32
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Model-based approaches to FMRI analysis

Woolrich, Mark January 2001 (has links)
No description available.
2

Investigating the BOLD effect

Sleigh, Alison January 2003 (has links)
No description available.
3

Cortical re-organisation of plasticity : applying fMRI to study disease

Reddy, H. January 2001 (has links)
No description available.
4

Functional magnetic resonance imaging : an intermediary between behavior and neural activity

Vakorin, Vasily 28 June 2007
Blood oxygen level dependent (BOLD) functional magnetic resonance imaging is a non-invasive technique used to trace changes in neural dynamics in reaction to mental activity caused by perceptual, motor or cognitive tasks. The BOLD response is a complex signal, a consequence of a series of physiological events regulated by increased neural activity. A method to infer from the BOLD signal onto underlying neuronal activity (hemodynamic inverse problem) is proposed in Chapter 2 under the assumption of a previously proposed mathematical model on the transduction of neural activity to the BOLD signal. Also, in this chapter we clarify the meaning of the neural activity function used as the input for an intrinsic dynamic system which can be viewed as an advanced substitute for the impulse response function. Chapter 3 describes an approach for recovering neural timing information (mental chronometry) in an object interaction decision task via solving the hemodynamic inverse problem. In contrast to the hemodynamic level, at the neural level, we were able to determine statistically significant latencies in activation between functional units in the model used. In Chapter 4, two approaches for regularization parameter tuning in a regularized-regression analysis are compared in an attempt to find the optimal amount of smoothing to be imposed on fMRI data in determining an empirical hemodynamic response function. We found that the noise autocorrelation structure can be improved by tuning the regularization parameter but the whitening-based criterion provides too much smoothing when compared to cross-validation. Chapter~5 illustrates that the smoothing techniques proposed in Chapter 4 can be useful in the issue of correlating behavioral and hemodynamic characteristics. Specifically, Chapter 5, based on the smoothing techniques from Chapter 4, seeks to correlate several parameters characterizing the hemodynamic response in Broca's area to behavioral measures in a naming task. In particular, a condition for independence between two routes of converting print to speech in a dual route cognitive model was verified in terms of hemodynamic parameters.
5

Functional magnetic resonance imaging : an intermediary between behavior and neural activity

Vakorin, Vasily 28 June 2007 (has links)
Blood oxygen level dependent (BOLD) functional magnetic resonance imaging is a non-invasive technique used to trace changes in neural dynamics in reaction to mental activity caused by perceptual, motor or cognitive tasks. The BOLD response is a complex signal, a consequence of a series of physiological events regulated by increased neural activity. A method to infer from the BOLD signal onto underlying neuronal activity (hemodynamic inverse problem) is proposed in Chapter 2 under the assumption of a previously proposed mathematical model on the transduction of neural activity to the BOLD signal. Also, in this chapter we clarify the meaning of the neural activity function used as the input for an intrinsic dynamic system which can be viewed as an advanced substitute for the impulse response function. Chapter 3 describes an approach for recovering neural timing information (mental chronometry) in an object interaction decision task via solving the hemodynamic inverse problem. In contrast to the hemodynamic level, at the neural level, we were able to determine statistically significant latencies in activation between functional units in the model used. In Chapter 4, two approaches for regularization parameter tuning in a regularized-regression analysis are compared in an attempt to find the optimal amount of smoothing to be imposed on fMRI data in determining an empirical hemodynamic response function. We found that the noise autocorrelation structure can be improved by tuning the regularization parameter but the whitening-based criterion provides too much smoothing when compared to cross-validation. Chapter~5 illustrates that the smoothing techniques proposed in Chapter 4 can be useful in the issue of correlating behavioral and hemodynamic characteristics. Specifically, Chapter 5, based on the smoothing techniques from Chapter 4, seeks to correlate several parameters characterizing the hemodynamic response in Broca's area to behavioral measures in a naming task. In particular, a condition for independence between two routes of converting print to speech in a dual route cognitive model was verified in terms of hemodynamic parameters.
6

Distinguishing alcohol related neurodevelopmental disorder from attention-deficit/hyperactivity disorder using psychological measures and fMRI

Woods Frohlich, Lindsay 13 September 2016 (has links)
Individuals with Alcohol Related Neurodevelopmental Disorder (ARND) and Attention-Deficit/Hyperactivity Disorder (ADHD) display similar deficits in behavioural, cognitive, and executive dysfunction symptoms; however, the underlying impairment in brain function and attention pathways is thought to be different. This study compared these two clinical groups, and healthy controls, using psychological assessments and functional magnetic resonance imaging (fMRI). The two clinical groups had significantly different scores on measures of overall intellectual functioning, working memory, and the conjunction trials on the fMRI assessment but could not be differentiated on other measures from rating scales, standardized psychological assessments, and performance data from fMRI tasks. The fMRI task accuracy variables were strongly correlated with related standardized psychological measures. All groups demonstrated difficulties with response inhibition compared to attention, and the clinical groups demonstrated more difficulties with attention and variability compared to the control group on a computer-paced Go/No-Go task. The comparison of a self-paced and a computer-paced Go/No-Go task indicated that the computer-paced task would be more appropriate to use with fMRI to assess cortical activation in response inhibition. It was found that the ADHD group had higher levels of cortical activation (indicating that more cognitive effort was require to reach the same level of behavioural performance) compared to the ARND group during the visual-spatial attention tasks, whereas the ARND group had higher levels of activation during the response inhibition and working memory tasks. Despite no significant differences in behavioural performance, the fMRI tasks helped to demonstrate different activation patterns that could help distinguish and differentially diagnose these two similar groups. / October 2016
7

Medial Temporal Lobe Function and the Perceptual Richness of Memory for Complex Personal and Laboratory Events

St-Laurent, Marie 16 August 2013 (has links)
Reliving the past requires the integration of multi-modal sensory details into a coherent mental impression of the initial event. In most people, memory for life episodes, or Autobiographical Memory (AM), is rich in sensory-perceptual elements that provide the vivid impression of travelling back in time. Abundant evidence indicates that the hippocampus plays a central role in AM recollection, but much research is still needed to determine which AM attributes engage the hippocampus at retrieval. My work assessed the relationship between hippocampal function and the perceptual richness of memory episodes. I designed a paradigm that captured the complexity of AM, and that manipulated perceptual richness while controlling for other AM confounds, such as recency, rehearsal, personal relevance, and “story” content. Participants studied and recalled perceptually enriched and impoverished laboratory events (film clips and written narratives, respectively) matched for the complexity of their storyline. An AM condition was also included for comparison. I tested healthy individuals and participants with unilateral medial temporal lobe epilepsy (mTLE), a clinical population with well documented hippocampal damage, on this paradigm. Perceptual richness was greatly reduced in people with mTLE, an effect that was most salient in the perceptually enriched conditions (AM and film clips). In a functional MRI version of this paradigm conducted on healthy individuals, I identified neural regions sensitive to the perceptual richness of AM and laboratory events, which included the anterior portion of the right hippocampus and other regions known to play a role in imagery and visual processing. In patients with right-lateralized mTLE, activation in these brain regions was markedly reduced in all memory conditions, which was consistent with the reduced perceptual richness I observed behaviourally. I reveal a clear relationship between hippocampal function and the perceptual richness of episodic memory, suggesting that the hippocampus plays a central role among brain regions that support the integration of multi-modal details into enriched memory experiences. My findings also advance our knowledge of how pathology and the nature of memory representation affect the neural correlates of episodic memory.
8

Alcohol-induced fragmentary blackouts : associated memory processes and neural correlates

Wetherill, Reagan Rochelle, 1979- 02 December 2010 (has links)
Alcohol-induced blackouts, or periods of anterograde amnesia without loss of consciousness, were a diagnostic indicator in Jellinek’s (1952) theory of alcoholism and have been correlated with alcohol use problems (Campbell & Hodgins, 1993; Goodwin, Crane, & Guze, 1969; Ryback, 1970; Tarter & Schneider, 1976). Other findings suggest that blackouts are a warning sign of problem drinking, but not a predictor of alcohol use disorders (Anthenelli, Klein, Tsuang, Smith, & Schuckit, 1994). Most published research on blackouts focuses on cognitive deficits among older alcohol-dependent adults, yet recent research indicates prevalence rates for blackouts as high as 50% among college students (White, Jamieson-Drake, & Swartzwelder, 2002). In addition, young adults who reported experiencing a blackout were later told that they had vandalized property, driven a car, or engaged in other risky behaviors without remembering (Buelow & Koeppel, 1995). Despite their high prevalence and associated negative consequences, relatively little is known about alcohol-induced blackouts or their neural, social, and behavioral correlates among non-dependent populations. The current research explored individual variation in memory functioning under sober and intoxicated conditions and alcohol’s effects on neural activation during memory processes. / text
9

Emotion processing in autism spectrum disorder

Philip, Ruth Clare Margaret January 2009 (has links)
With an estimated prevalence of ~1%, Autism Spectrum Disorder (ASD) is relatively common. Whilst accepted as a neurodevelopmental disorder, currently the diagnosis of autism is based on the observation of characteristic behaviour: deficits in language, communication and social skills in addition to unusual or restricted interests. Research in the condition has been approached with psychological and physiological methodology however a full understanding of the underlying neuropathology of autism is still unclear. Functional Magnetic Resonance Imaging (fMRI) has been employed to study face processing in ASD with varied results. The processing of other types of social cues has been far less extensively explored and similarly, whilst there have been some reports of aberrant neural responsiveness to emotion in ASD, this component of social cognition requires further study. In particular, it is unclear whether there is a specific deficit in processing faces in ASD or rather a global deficit in emotion processing which is present across stimulus types, sensory domains and emotions. In this study basic emotion labelling using a range of stimulus types has been investigated within the same ASD cohort. In comparison to a control group, deficits were apparent in the ASD group when processing emotion in face, whole body and voice stimuli. This indicates a global emotion processing deficit in ASD that cannot be fully accounted for by deficits in basic face processing alone. Processing neutral and emotional faces and static whole body images was subsequently investigated using fMRI. When neutral faces, neutral bodies, fearful faces and fearful bodies were contrasted with fixation baseline, both groups broadly recruited the expected network of brain regions. When the emotional condition was contrasted with the neutral condition for each stimulus type significant between groups differences were apparent. The bilateral inferior parietal lobe responded significantly differently in response to facial emotion and the right supplementary motor area and superior temporal sulcus region was differentially activated in response to emotion in body stimuli. Findings reported here suggest that there are wide ranging social deficits in ASD which relate to the processing of a variety of social cues. fMRI evidence suggests that these deficits have a neural basis, in which elements of the social brain, including regions associated with mirror neuron function, activate in an atypical manner in ASD.
10

FUNCTIONAL MAGNETIC RESONANCE IMAGING STUDY OF PAIN AND EMOTION

Davis, Claude Ervin 01 January 2003 (has links)
Neuroscience research has followed two fairly distinct paths in investigating central neural mechanisms of pain and emotion. Rarely have studies been conducted which intentionally combined painful and emotional stimulation while observing brain function. Theories of emotion and pain processing predict an interaction between pain and emotion such that emotional states may serve to both increase or decrease pain. This increase or decrease may also correspond to different effects on different dimensions of the overall pain experience as defined in pain neuromatrix theory. Theories of emotion begin with emotions as interpretations of bodily states, to more contemporary theories focusing on the functions of emotions. These emotion theories predict neuroanotomic relations between emotion and pain in the brain. Similarly neuromatrix theory predicts an affective dimension of pain experience, which has been defined in terms of pain unpleasantness and secondary affect, emphasizing the role of emotion in pain experience. To further explore the relationship between pain and emotion, in the present study, painful heat stimulation is applied to the face while simultaneously conducting whole brain imaging using functional magnetic resonance imaging (fMRI). Also personal episodes involving anger, fear, and neutral emotion are recalled during fMRI both with, and without, painful heat stimulation. Similar brain regions are involved in processing pain, anger, and fear, and these responses compare favorably with those in the literature. The results also demonstrate that simultaneous emotional episode recall modulates the patterns of brain activity involved in pain. Anger recall especially seems to increase pain-related activity. The study allows greater understanding about the way that the brain's emotional processing networks for fear and anger affect pain experience and how pain affects the emotional processing network to produce affective experience, such as fear and anger, related to pain. Further application of these procedures to patients with chronic pain can aid understanding of central pathological mechanisms involved.

Page generated in 0.1839 seconds