Contradictory results have been shown in studies measuring the effect of muscle fatigue on the level of synchrony between the oscillatory, cortical and muscular electrical activities (also known as corticomuscular coupling). In every study, the standard method (coherence) used to measure the level of synchrony takes into account both the amplitude and phase of the two signals. However, the use of the phase lock value (PLV) has been over looked as a method for determining the level of synchrony. While the PLV is modulated purely by the phase between the two signals, it is unaffected by any amplitude variation. This study aims to determine whether amplitude variations in electroencephalography (EEG) and electromyography (EMG) could have caused the contradictory results when comparing pre-,during and post-fatigue measures of corticomuscular coupling, which consequently affected the conclusions drawn regarding the monitoring of fatigue by the central nervous system. A determination will be made regarding the contradictions by directly comparing the two methods (coherence and PLV) on the same dataset of simultaneously measured EEG and EMG signals throughout an isometric pre-, during and post-fatigue task.

Blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) experiments are normally performed separately. The idea of extracting inherently co-registered activation/connectivity maps and diffusion parameters has resulted in efforts to develop methods for simultaneous fMRI and DTI data acquisition. Recently, a 3D echo planar imaging (EPI) acquisition was successfully inserted after each DTI volume to perform real-time motion correction, with the two sequence protocols remaining separate. We examined using a single 3D EPI acquisition, inserted following each DTI volume acquisition (hereafter called the single nav sequence), modified to acquire BOLD resting state fMRI (rs-fMRI) data. We also investigated inserting a second 3D EPI acquisition in the middle of each DTI volume acquisition (hereafter called the double nav sequence) to increase fMRI temporal resolution. Two adult subjects were scanned with the navigated sequences and the standard separate 2D EPI BOLD and DTI acquisitions for comparison. Preprocessing and analysis of data was performed using FATCAT, AFNI , FSL and in-house Python scripts. Four standard resting state networks (RSNs) were visually identified using the navigated diffusion sequences. While RSNs were apparent in the single nav case, they were quite noisy and in some cases entire regions did not show connectivity. The double nav connectivity maps were more similar to the standard BOLD connectivity maps in terms of the spatial extent of the regions showing connectivity to the seed. The whole brain distributions of fractional anisotropy (FA) and mean diffusivity (MD) were similar among the different acquisition protocols. The jackknife standard error was comparable between the navigated and standard protocols. Further comparisons of diffusion data made using probabilistic tractography and connectivity matrices showed overall small differences indicating that connections derived from the standard DTI, single nav and double nav protocols were overall similar. We have therefore shown a significant "proof of concept" of successfully acquiring simultaneous DTI and rs-fMRI data, and therefore for investigating brain structural and functional connectivity simultaneously.

Includes abstract. / Includes bibliographical references (leaves 84-91). / Maternal drinking during pregnancy is a significant problem in the Western Cape, South Africa, with an accompanying high incidence of children diagnosed with foetal alcohol spectrum disorder (FASD). Little is known about the neural correlates governing the disorder that manifest as behavioural abnormalities and cognitive impairments, particularly in arithmethic calculation, repeatedly reported in affected children. The effect of prenatal alcohol exposure on number processing in children was investigated in a functional magnetic resonance imaging (fMRI) study (Meintjes et al., 2007). The results indicate significant differences in activation between alcohol-exposed and non-exposed control children during Exact Addition and Proximity Judgement tasks. This raised the question of whether the groups of children differ in functional connectivity during the number processing tasks. Therefore, the objective of this study was to analyse connectivity between functionally specialised brain areas in the previously collected fMRI data. The fMRI data of 14 controls and 7 alcohol-exposed children for Exact Addition and 15 controls and 9 alcohol-exposed children for Proximity Judgement was available for analysis. A primary aim was to determine normal functional connectivity in control children during number processing and a secondary aim, to investigate any differences in functional connectivity in children with FASD.

Includes abstract. / Includes bibliographical references. / Lower motor neuron damage often results in flaccid paralysis in which the affected muscles are unable to be stimulated artificially via the supplying nerve. Such damage is common in patients who suffer from spinal cord injury and Multiple Sclerosis. Current practice for artificial recovery of muscle function involves stimulating the muscles directly by means of Functional Electrical Stimulation (FES), which requires 100-1000 times more current than that required for nerve stimulation, thus presenting the risk of pain receptor activation. A potential alternative exists in chemical stimulation by means of administration of the neurotransmitter, Acetylcholine (ACh). This study investigates the potential of this possibility by examining the response of two muscle types to extracellular administration of ACh.

Includes bibliographical references (p. 104-111).

Includes bibliographical references (leaves 141-143).

This thesis aims to investigate the feasibility of using perfluorobutane phase-shift nanoemulsions (PFB PSNE) to facilitate mechanical ablation and its potential as a treatment for brain tumors. PFB PSNE are cavitation nuclei that can be acoustically vaporized, a process which is termed acoustic droplet vaporization (ADV). The vaporized bubbles can be cavitated by ultrasound at different intensities leading to a range of bioeffects that can be exploited for different therapies, including blood-brain barrier disruption, thermal ablation, and mechanical ablation. In this thesis, the research was focused on mechanical ablation using PFB PSNE. The thesis has been designed to test two major hypotheses: 1. PFB PSNE could significantly reduce the power and pressure needed to create lesions inside the brain through inertial cavitation while avoiding pre-focal damage. 2. PFB PSNE ablation can destroy a tumor at the targeted region, reducing tumor growth and prolonging survival. A series of in vitro and in vivo experiments were designed to test these two central hypotheses. PFB PSNE were activated at acoustic pressure amplitudes of 1.5–2.5 MPa, and the vaporization/inertial cavitation threshold was identified from the acoustic emissions. The inertial cavitation of PFB PSNE resulted in hemorrhagic and ischemic damage in the brain, and these effects were evaluated using magnetic resonance imaging (MRI). In experiments with a clinically relevant setup comparing PFB PSNE with microbubbles (MBs), PFB PSNE-facilitated ablation improved the localization of the damage and avoided effects in the beam path typically observed with MB-nucleated cavitation. Further, PFB PSNE-facilitated ablation in a rat glioma model produced a higher percentage of tumor death (89.4% vs. 11.1% for PFB PSNE and MBs). PFB PSNE-facilitated ablation also prolonged the survival of glioma rats with a significant increase of median survival (27 vs. 25 days; p = 0.00126). Overall, these results demonstrate that PFB PSNE are cavitation nuclei, which are more effective and safer for brain tumor ablation via improved localization and reduced effects in the ultrasound beam path. / 2021-09-29T00:00:00Z

The dissertation investigated the influence of stimulus characteristics, electroencephalographic (EEG) electrode location and three signal processing methods on the spectral signal to noise ratio (SNR) of Steady State Visual Evoked Potentials (SSVEPs) with a view for use in Brain-Computer Interfaces (BCIs). It was hypothesised that the new spectral baseline processing method introduced here, termed the 'activity baseline', would result in an improved SNR.

Fetal alcohol syndrome (FAS) is a condition which is caused by excessive consumption of alcohol by the mother during pregnancy. A FAS diagnosis depends on the presence of growth retardation, central nervous system and neurodevelopment abnormalities together with facial malformations. The main facial features which best distinguish children with and without FAS are smooth philtrum, thin upper lip and short palpebral fissures. Diagnosis of the facial phenotype associated with FAS can be done using methods such as direct facial anthropometry and photogrammetry. The project described here used information obtained from stereo facial images and applied facial shape analysis and pattern recognition to distinguish between children with FAS and control children. Other researches have reported on identifying FAS through the classification of 2D landmark coordinates and 3D landmark information in the form of Procrustes residuals. This project built on this previous work with the use of 3D information combined with texture as features for facial classification. Stereo facial images of children were used to obtain the 3D coordinates of those facial landmarks which play a role in defining the FAS facial phenotype. Two datasets were used: the first consisted of facial images of 34 children whose facial shapes had previously been analysed with respect to FAS. The second dataset consisted of a new set of images from 40 subjects. Elastic bunch graph matching was used on the frontal facial images of the study populaiii tion to obtain texture information, in the form of jets, around selected landmarks. Their 2D coordinates were also extracted during the process. Faces were classified using knearest neighbor (kNN), linear discriminant analysis (LDA) and support vector machine (SVM) classifiers. Principal component analysis was used for dimensionality reduction while classification accuracy was assessed using leave-one-out cross-validation. For dataset 1, using 2D coordinates together with texture information as features during classification produced a best classification accuracy of 72.7% with kNN, 75.8% with LDA and 78.8% with SVM. When the 2D coordinates were replaced by Procrustes residuals (which encode 3D facial shape information), the best classification accuracies were 69.7% with kNN, 81.8% with LDA and 78.6% with SVM. LDA produced the most consistent classification results. The classification accuracies for dataset 2 were lower than for dataset 1. The different conditions during data collection and the possible differences in the ethnic composition of the datasets were identified as likely causes for this decrease in classification accuracy.

The puncturing of blood vessels is often a "hit and miss" procedure which may take even a skilled physician considerable time to perform. Perhaps even more important than the time taken by medical personnel is the trauma inflicted on patients when the procedure is unnecessarily prolonged. A needle guide was developed, based on the well-known Doppler ultrasound principle. Two transducers, on sliding bars, are used to locate the vessel. A unique mechanical arrangement was devised for aiming the needle at the intersection point of the two ultrasonic beams. An account is given of the theory, engineering philosophy, design parameters and step-by-step development of the guide. Full mechanical and electronic drawings and photographs of the prototype also appear in this work.