No description available.

Metamemory is defined as the knowledge about one's memory capabilities and about strategies that can aid memory (Shimamura, 1994). One particularly intriguing type of metamemory judgment is a tip-of-the-tongue experience, which refers to a strong feeling that a target word, though presently not recalled, is known and on the verge of being produced. Older adults report more TOT experiences than young adults. However, there is great variability among older adults in performance on memory and executive function tasks, and it is unknown whether subsets of older adults experience more TOT states. Additionally, the neural correlates of successful retrieval, TOTs, and unsuccessful retrieval in aging have not been studied. In the studies reported here, the relationship between frontal and medial temporal neuropsychological factor scores (see Glisky et al., 1995) and performance on metamemory tasks was examined. Importantly, this was the first study to examine the neural correlates of tip-of-the-tongue experiences in older adults. In an event-related fMRI design, participants viewed famous and novel faces and were asked to respond regarding successful retrieval, unsuccessful retrieval, or tip-of-the-tongue experiences. Results show that, as a group, older adults had activation in the medial prefrontal cortex and anterior cingulate during tip-of-the-tongue states, consistent with similar studies in young adults (Maril et al., 2001; Pannu et al., 2004, Schnyer et al., 2005). Additionally, activations in lateral prefrontal cortex and medial temporal areas during the task varied systematically with frontal and temporal lobe factor scores. These results provide evidence for differences in neural activation between groups of healthy older adults characterized on the basis of neuropsychological performance, and shed light on the neural underpinnings of the tip-of-the-tongue states in aging.

No description available.

The designs of two functional magnetic resonance imaging-compatible electronic interfaces for use in neuropsychological studies involving musical tasks are presented. The devices, a two-button response box in the form of a computer mouse and a piano keyboard, were designed for rhythmic tapping and piano performance tasks, respectively. In order to correlate changes in neural activation acquired through magnetic resonance imaging (MRI) with task performance, the electronic collection of behavioural data, such as the timing of button or key presses was required. These behavioural measures were captured electronically and communicated to a host computer for synchronization with feedback, stimuli, and the MRI scanner itself. As well, data was logged for offline analysis. Due to the intense and volatile electromagnetic fields, most commercially-available electronic interfaces do not function properly and can even pose a serious safety hazard within the MRI scanner environment. Therefore these custom-designed interfaces were free of ferromagnetic parts and all electronic components were relegated to the control room outside of the scanner environment. Acquisition of button and key presses was accomplished using fibre optic sensors, which are immune to electromagnetic interference. The devices performed successfully within the scanner, and MRI scans showed no image artifacts caused by the prototypes. Sensing of key and button transition velocity was sufficient after extensive calibration. Next generation prototypes are planned and will implement more robust and tighter tolerance manufacturing, improved sensing techniques, the acquisition of isometric forces, and an auto-calibration scheme.

No description available.

No description available.

This thesis addresses the problem of producing three-dimensional constrained Delaunay triangulated meshes from the sequential two dimensional MRI medical image slices. The approach is to generate the volumetric meshes of the scanned organs as a result of a several low-level tasks: image segmentation, connected component extraction, isosurfacing, image smoothing, mesh decimation and constrained Delaunay tetrahedralization. The proposed methodology produces a portable application that can be easily adapted and extended by researchers to tackle this problem. The application requires very minimal user intervention and can be used either independently or as a pre-processor to an adaptive mesh refinement system. / Finite element analysis of the MRI medical data depends heavily on the quality of the mesh representation of the scanned organs. This thesis presents experimental test results that illustrate how the different operations done during the process can affect the quality of the final mesh.

Functional magnetic resonance imaging (fMRI) enables non-invasive investigation of the neural functions with excellent spatial resolution. Although fMRI has primarily been developed in young adult populations, its use is becoming widespread in paediatrics. However, there are many differences, both behavioural and physical, between adults and children requiring adjustments to imaging and analysis methodology to optimise the results in children. This thesis examines fMRI analysis methodology to improve the detection of developmental changes in the brain. The work uses an emotional and familiar face paradigm that elicits strong BOLD fMRI responses in the fusiform, a region that is still developing across childhood. This face paradigm also enables the comparison of the fusiform responses to the primary visual cortex to link to extensive results in the literature. Thirty five 4-8 year old children and fourteen adults (18-30 years old) were scanned. To address the concern of anatomical size differences between the brains of adults and children, the anatomical variability of the fusiform was measured and the validity of stereotaxic transformation into an adult template was confirmed for the children. To investigate the effect of threshold settings between the adults and children, individual subject analyses of the peak activation location, estimated signal percent change and noise values were calculated using the general linear model (GLM). Similar functional peak locations between individuals were quantitatively selected using a novel application of the activation likelihood estimation (ALE). Also, several different preprocessing steps were evaluated for their ability to correct for the increased motion frequently seen in children, in a quantitative framework (NPAIRS) using canonical variates analysis (CVA), a data driven multivariate model as well as the standard univariate GLM. Functional differences between the adults and the children were identified in the fusiform by applying these optimised procedures. The results of this thesis demonstrate that thresholding and preprocessing pipelines must be made in a group-specific fashion. These methods can also be extended to elderly populations, enabling the investigation of the complete ageing spectrum with fMRI.

Functional magnetic resonance imaging (fMRI) enables non-invasive investigation of the neural functions with excellent spatial resolution. Although fMRI has primarily been developed in young adult populations, its use is becoming widespread in paediatrics. However, there are many differences, both behavioural and physical, between adults and children requiring adjustments to imaging and analysis methodology to optimise the results in children. This thesis examines fMRI analysis methodology to improve the detection of developmental changes in the brain. The work uses an emotional and familiar face paradigm that elicits strong BOLD fMRI responses in the fusiform, a region that is still developing across childhood. This face paradigm also enables the comparison of the fusiform responses to the primary visual cortex to link to extensive results in the literature. Thirty five 4-8 year old children and fourteen adults (18-30 years old) were scanned. To address the concern of anatomical size differences between the brains of adults and children, the anatomical variability of the fusiform was measured and the validity of stereotaxic transformation into an adult template was confirmed for the children. To investigate the effect of threshold settings between the adults and children, individual subject analyses of the peak activation location, estimated signal percent change and noise values were calculated using the general linear model (GLM). Similar functional peak locations between individuals were quantitatively selected using a novel application of the activation likelihood estimation (ALE). Also, several different preprocessing steps were evaluated for their ability to correct for the increased motion frequently seen in children, in a quantitative framework (NPAIRS) using canonical variates analysis (CVA), a data driven multivariate model as well as the standard univariate GLM. Functional differences between the adults and the children were identified in the fusiform by applying these optimised procedures. The results of this thesis demonstrate that thresholding and preprocessing pipelines must be made in a group-specific fashion. These methods can also be extended to elderly populations, enabling the investigation of the complete ageing spectrum with fMRI.

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.