Saudi Cultural Missions Theses & Dissertations
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Item Restricted The therapeutic role of Non-invasive Temporal Interference (TI) stimulation in Traumatic Brain Injury(Imperial College London, 2024) Alkhawajah, Batool; Sastre, Magdalena; Hervas, Laura AbelleiraThe therapeutic role of Non-invasive Temporal Interference (TI) stimulation in Traumatic Brain Injury Traumatic Brain Injury (TBI), characterized by cranial compression leading to neural loss and white matter damage. IT is associated with the development of severe neurological disorders such as Alzheimer's and dementia. Temporal interference (TI) stimulation has emerged as a recent therapeutic modality for severe neurological and psychiatric disorders, such as Alzheimer's disease (AD) and dementia. TI stimulation delivers two frequencies to the brain, generating an electrical field with nuanced frequency differentials, thereby non-invasively targeting specific brain regions. Experimental validation on animal models and healthy subjects has revealed significant improvements in cognitive function following TI stimulation. Recognizing shared pathological mechanisms between TBI and AD, our laboratory has initiated investigations into the potential anti-inflammatory effects of TI stimulation in the context of TBI. A conducted experiment applied TI stimulation targeting the ipsilateral hippocampus in a mild Closed head injury (CHI) model, with a single impact, resulting in observed memory enhancement. However, the cellular and molecular consequences of TI stimulation on the brain remain an unexplored realm. This research project seeks to delineate these changes through various staining techniques targeting Glial Fibrillary Acidic Protein (GFAP), microglia, and neurogenesis. Floating brain sections from three distinct groups: CHI-TI, CHI control, and sham were subjected to staining, enabling the quantification of alterations in the hippocampal region and cortex. Our findings unveil that TI stimulation augments activated microglial populations, diminishes astrocyte presence, and exerts no apparent impact on neural proliferation. This scientific endeavour contributes to the elucidation of the neurobiological effects of TI stimulation, paving the way for a deeper understanding of its therapeutic potential in TBIs.17 0Item Restricted Neuroplasticity and Systematic Audiovisual Training in Virtual Reality: A Multimodal MRI Investigation(University of Liverpool, 2024-03) Alwashmi, Kholoud; Meyer, GeorgThe integration of information from different sensory modalities is a fundamental process that enhances perception and performance. This study explores the audio-visual (AV) integration and its impact on behavioural performance using virtual reality (VR). The research involved twenty healthy participants who underwent daily VR training for four weeks, focusing on an AV adaptation of a scanning training paradigm used in hemianopia rehabilitation. The investigation aimed to understand how functional brain changes contribute to improvements in behavioural performance during AV learning tasks, and how microstructural changes in white matter (WM) tracts, measured through diffusion tensor and kurtosis imaging (DTI, DKI), are linked to functional connectivity changes in relevant brain areas. The results revealed a significant reduction in the response time (RT) after training for the voluntary eye movement task (the trained task). Behavioural performance was improved in both visual and AV conditions, with the latter exhibiting faster RT facilitated by audio cues. This learning effect transferred to two untrained tasks, a visual search task and an involuntary visual task. Functional magnetic resonance imaging (fMRI) demonstrated increased activation in multisensory brain regions involved in early-stage AV processing, the thalamus, inferior parietal lobe, and cerebellum, which was correlated with behavioural enhancements. DTI analysis indicated a decrease in mean diffusivity (MD) in the superior longitudinal fasciculus II (SLF II), connecting frontal and parietal regions, correlating significantly with observed behavioural gains. Additionally, fractional anisotropy (FA) increased in optic radiations post-training, connecting the thalamus with visual areas. Functional connectivity analysis revealed a significant increase in functional connectivity between primary visual and auditory cortices post-training, supported by DKI microstructural changes in these regions and the sagittal stratum, encompassing WM tracts connecting these lobes. These findings highlight learning-induced functional and microstructural changes in extended brain networks contributing to AV integration and attention. It also demonstrates the complementary nature of the DTI and DKI, providing insights into task-relevant brain networks. Overall, the complex relationship between functional and microstructural brain adaptations, alongside functional connectivity changes, underscores how immersive VR training promotes multisensory integration and neuroplasticity. Understanding these dynamics could inform tailored interventions and optimize training paradigms for enhanced sensory processing and rehabilitation outcomes.16 0Item Restricted Neural changes during short-term novel spoken and sign language learning: fMRI and DTI studies(2023-01-31) Alotaibi, Sahal; Meyer, GeorgIt is conventionally thought that language processing is supported by two different brain areas: Broca's area for language production, and Wernicke's area for comprehension. Recent neuroimaging data, however, has shown that the brain networks underlying language processing are more complex than initially thought and closely integrated for spoken language and sign language. In this thesis, we conducted two longitudinal studies at three different approaches, behavioural, functional and structural imaging, which investigate the neural processing underlying spoken and sign language learning. In the first study, Magnetic Resonance Imaging (MRI) brain scans were taken from 20 English-speaking healthy volunteers before and after attending a novel spoken language-training course, learning phonetically minimal distinctions in Arabic that are allophones in the participant’s first language, of one hour for three consecutive days. The same paradigm was applied in the second study for 26 Englishspeaking healthy volunteers who were taught British sign language. Again, minimal contrasts between sign language gestures were learnt. Behavioural results for both studies show performance improvement in all variables including a phonetic discrimination task, and a pronunciation task for spoken language, and a gesture discrimination task and a signing task for the sign language group. Functional MRI results illustrate significant brain activity increasing in multiple language regions including left inferior frontal gyrus (IFG), bilateral middle temporal gyrus, left angular gyrus and the right cerebellum. Moreover, functional connectivity increased significantly after training between these areas. These areas also show significant DTI changes represented by increasing fractional anisotropy (FA) and decreasing in mean diffusivity (MD) and radial diffusivity (RD). The fMRI and DTI changes are correlated with the participant’s behavioural improvement. These findings reveal a high degree of similarity in the neural activity underlying signed and spoken languages. Furthermore, the rapid neural changes noted as an impact of short-term learning oppose the conventional belief that brain changes associated with language learning require long training periods.29 0Item Restricted Neural Mechanisms of Treatment for Mental Disorder(2023-06) Shalabi, Abdulrhman; Liddle, Peter; Liddle, Elizabeth“Cognitive control” refers to the ability to regulate thoughts and actions in the service of goals or plans (Braver, 2012). Coordination between the central and peripheral autonomic nervous systems (ANS) maintains arousal and attention levels, which are essential for effective cognitive control. Diamond (2013) proposed a cognitive control model that builds on three core cognitive functions: cognitive flexibility, inhibitory control, and working memory. Abnormality in active inhibitory cognitive control is implicated in a broad range of psychiatric and personality disorders, including schizophrenia, attention deficit hyperactivity disorder (ADHD), impulsivity, and substance abuse, among many others. Transcranial direct current stimulation (tDCS) and cognitive training are two neuromodulation techniques which have the potential to modulate cortical functions to introduce long-lasting neuronal plasticity. The antisaccade task is a visual inhibitory control task frequently used to assess cognitive control. It requires the participant to suppress an automatic stimulus-driven saccadic eye movement and instead make a goal-driven saccade in the opposite direction. In this thesis, by conducting two separate studies, we used the antisaccade task to examine the effect of tDCS and computerised cognitive training on inducing neuroplastic changes for the oculomotor control network (OCN). Chapter 1¢introduces relevant concepts to the subject of this thesis with a technical account of the methods used. The details of the first study are discussed in Chapter 2 - Chapter 4, where we used eye-tracking during antisaccade performance with the continuous assessment of cortical activity using Magnetoencephalography (MEG). Chapter 2 will discuss the short-term neuroplastic changes introduced by the tDCS on the functional connectivity within the resting state networks assessed using MEG. We found evidence of increased connectivity following the engagement in the antisaccade task for both active tDCS and sham conditions, but with different spatial patterns. Following tDCS delivered over the frontal cortex, there was increased connectivity with the frontal cortex. In contrast, in the sham condition there was increased connectivity with the posterior cortex. The effects of tDCS stimulation on the ANS activity during the task performance were further assessed via pupillometry as a measure of Locus Coeruleus (LC) activity in Chapter 3. Our results showed that faster pupil dilation, reflecting increased arousal and sympathetic activity, was associated with faster saccade reaction times. In Chapter 4, we investigated the immediate effects of tDCS stimulation on the cerebral cortex during active cognitive inhibition followed by a correct saccadic response. The tDCS introduced neuromodulatory changes in the putative Alpha and low-Beta band during the anticipatory and post-stimulus periods, reflecting enhanced cortical engagement in a task-beneficial pattern. Chapter 5 reports on the second study in which we used functional magnetic resonance imaging (fMRI) to evaluate the neuromodulatory effects of prolonged computerised cognitive training games (RECOGNeyes) on the resting state functional connectivity of the OCN and pupil dilation. Following gaze-control training, the connectivity within the left hemisphere was strengthened, while the intra-right hemisphere and the interhemispheric connectivity were diminished. Chapter 6 provides a summary of the findings and concluding remarks. Our result furthers our knowledge of the processes involved in the performance of the antisaccade task, the mechanisms of action and the neuroplastic effects of two neuromodulation techniques. However, the exact mechanisms underlying these methods' beneficial effects demand further exploration.33 0