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published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Ming Lui. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 44-53). / Abstracts in English and Chinese. / Introduction --- p.6-22 / Method --- p.23-30 / Results --- p.31-34 / Discussion --- p.35-42 / References --- p.43-51 / Tables --- p.52-55 / Figure Caption --- p.56 / Figures --- p.57-62

Reading requires the successful recruitment and coordination of brain networks to translate visual symbols into phonemes, which are then sequenced to match speech sounds and matched onto semantic representations. Although phonemic awareness is understood to be a core deficit associated with reading disability, neuroimaging has demonstrated an association between poor reading and disruption to various interrelated areas in the brain. This includes one of the major visual pathways, the magnocellular pathway, which contributes to the dorsal pathway in the brain and the processing of motion. For at least two decades, researchers have observed differences in motion processing, supported by the magnocellular pathway, between individuals with and without dyslexia (Eden et al., 1996; Gori et al., 2016; Livingstone et al., 1991; Wilmer, 2004). Further, psychometric studies report an association between reading ability and dorsal stream sensitivity in adults and in children before and after learning to read (Boets et al., 2011; Kevan & Pammer, 2009). Studies of the development of the major visual pathways have suggested that the magnocellular pathway follows a protracted course of development, which raises the possibility that it is vulnerable to pathological change during development and also has the potential for greater plasticity (Armstrong et al., 2002; Stevens & Neville, 2006). To explore the potential differences in early-stage visual processing, this dissertation study investigated whether neurophysiological measures, as indexed by event-related potentials (ERP), may differ between adults with and without dyslexia to stimuli tailored to evoke a response from each of two major visual pathways: magnocellular and parvocellular. The P1 component was elicited in response to motion stimuli designed to probe magnocellular pathways, and the N1 component was elicited in response to color stimuli designed for parvocellular processing. Group comparisons revealed statistically significant group differences in P1 amplitude for the motion/magnocellular condition, but no differences were found for N1 ERP measures for the parvocellular/color condition. Moderate to strong correlations between P1 measures in response to the magnocellular/motion condition were observed in relation to specific behavioral assessments: nonverbal reasoning and memory, orthographic choice, the word identification subtest from the Woodcock Reading Mastery Test (3rd edition: WRMT-III, Woodcock, 2011), and the sight word efficiency subtest from the Test of Word Reading Efficiency (2nd edition: TOWRE-2, Wagner, Torgesen, & Rashotte, 2011). These results are indicative of an early-stage visual processing disruption in individuals with dyslexia observable at the level of the brain. Due to the compounding impact of even small disruptions of sensory and cognitive processing on learning, refining our knowledge of the underlying neural mechanisms of reading may permit earlier identification and potentially more focused interventions that could yield better outcomes for struggling readers. Additionally, the association of those differences with measures of word decoding will inform further research into the underlying neural mechanisms that may contribute to dyslexia and skilled reading.

In my Event-Related Potential studies, these two factors are analyzed collectively. Two dichotic listening experiments, one word phonological priming experiment, and one sentence semantic violation experiment are conducted. The results indicate that the linguistic role (e.g. semantics) causes the tone processing toward the left side, whereas the physical property causes the tone processing toward the right side. / In this dissertation, I discuss the effects of the linguistic role and the physical property on the hemispheric specialization (lateralization) of the lexical tones. In the previous studies of lateralization, there are two contradictory hypotheses. One emphasizes the linguistic role and predicts a left lateralization of tone perception, while the other emphasizes the physical property and predicts a right lateralization of tone perception. Both hypotheses have their supporting evidence. / No previous tone lateralization studies have analyzed the underlying factors. Following the philosophy that language is built upon multiple cognitive functions, I further examine the effects of semantic memory and pitch processing on the lateralization of tones in various language tasks. My findings help bridge the previous theoretical discrepancies and unify the conflicting experimental results regarding tone lateralization. / Shuai, Lan / Adviser: William S-Y. Wang. / Source: Dissertation Abstracts International, Volume: 73-01, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 144-153). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Recent research has shown that distinct event-related potential (ERP) signatures are associated with switching between languages compared to switching between dialects or registers (e.g., Khamis-Dakwar & Froud, 2007; Moreno, Federmeier & Kutas, 2002). The current investigation builds on these findings to examine whether contrastive and non-contrastive morphosyntactic features in English elicit differing neural responses in bidialectal speakers of African American English (AAE) and Mainstream American English (MAE), compared to monodialectal speakers of MAE. Event-related potentials (ERPs) and behavioral responses (response types and reaction time) to grammaticality judgments targeting a contrasting morphosyntactic feature between MAE and AAE are presented as evidence of dual-language representation in bidialectal speakers. Results from 30 participants (15 monodialectal; 15 bidialectal) support the notion that bidialectal populations demonstrate distinct neurophysiological profiles from monolingual groups as indicated by a significantly greater P600 amplitude from 500ms – 800ms time window in the monodialectal group, when listening to sentences containing contrasting features. Such evidence can support the development of linguistically informed educational curriculums and clinical approaches from speech-language pathologists, by elucidating the differing underlying processes of language between monodialectal and bidialectal speakers of American English.

Ho, Pui Kwan. / "November 2010." / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 68-75). / Abstracts in English and Chinese. / Acknowledgements --- p.i / Abstract --- p.ii / List of figures --- p.vi / List of tables --- p.viii / Abbreviations --- p.ix / Chapter Chapter 1. --- Introduction / Chapter 1.1. --- Overview --- p.1 / Chapter 1.2. --- Thesis organization --- p.6 / Chapter Chapter 2. --- Background / Chapter 2.1. --- Brain structure and its functional organization --- p.8 / Chapter 2.2. --- Introduction to lateralization investigation techniques --- p.13 / Chapter 2.2.1. --- Lesion studies and Wada test --- p.13 / Chapter 2.2.2. --- Dichotic listening --- p.14 / Chapter 2.2.3. --- Functional Magnetic Resonance Imaging (fMRI) --- p.15 / Chapter 2.2.4. --- Electroencephalography(EEG) & event-related potential(ERP) --- p.16 / Chapter 2.2.5. --- Other brain imaging techniques --- p.20 / Chapter 2.2.6. --- Comparing different brain-imaging techniques in this study --- p.20 / Chapter 2.3. --- Literature review and the current work --- p.21 / Chapter 2.3.1 --- "The functional and acoustic ""dichotomy""" --- p.22 / Chapter 2.3.2. --- Studies on lateralization of tones without linguistic context --- p.25 / Chapter 2.3.3. --- Studies on lexical tone lateralization --- p.27 / Chapter 2.3.4. --- The current work ´ؤ aim and hypothesis --- p.34 / Chapter Chapter 3. --- Methodology / Chapter 3.1. --- Stimuli --- p.36 / Chapter 3.2. --- Subject --- p.41 / Chapter 3.3. --- Task design --- p.41 / Chapter 3.4. --- ERP recording and data processing --- p.44 / Chapter Chapter 4. --- Results and discussions / Chapter 4.1. --- Behavioural data analysis --- p.46 / Chapter 4.2. --- ERP data analysis --- p.48 / Chapter 4.3. --- Discussions --- p.52 / Chapter Chapter 5. --- Further discussions / Chapter 5.1. --- Is lateralization of lexical tone language-specific? --- p.57 / Chapter 5.2. --- Toward a model of speech lateralization --- p.59 / Chapter 5.3. --- An implication on tone feature systems --- p.60 / Chapter Chapter 6. --- Conclusion / Chapter 6.1. --- Conclusion --- p.65 / Chapter 6.2. --- Future work --- p.67 / References --- p.68 / Appendix / Chapter A.1. --- Edinburgh handedness test --- p.76 / Chapter A.2. --- Handedness scores --- p.77

In this study, I looked at the effects of sound level, temperature and dehydration/hypernatremia on the brainstem auditory evoked potential (BAEP) of four species of anuran amphibians (Rana pipiens, Rana catesbeiana, Bufo americanus and Bufo terrestris). The BAEP was used because it allowed me to monitor both the peripheral and central aspects of auditory nervous function simultaneously and over a long period of time.

Introduction: Psychophysical and electrophysiological techniques have shown that chromatic contrast sensitivity improves between infancy and adolescence. In adults, electrophysiological and psychophysical methods usually agree. However, in infants electrophysiological techniques may underestimate ability to see chromatic contrast (Suttle et al., 2002). It is not known if the discrepancy between electrophysiological and psychophysical methods continues during childhood nor whether the chromatic VEP can be used as an indicator of colour perception in children. Purpose: To investigate the transient L-M chromatic visual evoked potential and its ability to indicate perception (psychophysical thresholds) of chromatic stimuli in children and adults. In particular, to determine whether a discrepancy between VEP and psychophysical L-M thresholds exists during childhood and if so, to gain some understanding about the nature of the discrepancy. Methods: Transient chromatic VEPs were recorded in children (aged 4.5-13 years) and adults (aged 20-40 years). VEP thresholds were compared with psychophysical thresholds (within-subjects comparison). Because the VEPs of the children were less intra-individually repeatable in morphology than those of the adults, post-hoc objective analysis of the VEPs, linear (Fourier) and nonlinear dynamical (Grassberger and Procaccia's (1983) correlation dimension) analyses, was conducted. Results: VEP and psychophysical estimates of chromatic contrast thresholds agreed using a variety of methods in the adults. In the children, however, the objective methods of assessment (extrapolation from Fourier-derived amplitudes and the correlation dimension) were more accurate than the methods that employed subjective evaluations of VEP morphology. Conclusion: The L-M transient chromatic VEPs of both children (aged 4.5-13 years) and adults appear to contain chromatic information, even in the absence of repeatable VEP morphology and should therefore be able to indicate chromatic perception (psychophysical thresholds). However, the chromatic information may be present as a nonlinear dynamical signal, which may require objective methods (Fourier analysis, the correlation dimension) to reveal the chromatic signal. The greater intra-individual variability of VEP morphology in children compared to adults may reflect poorer precision when switching between cortical states in children's brains. Alternatively, interactions between the immature visual system of the children and their general EEG may occur. Children's VEPs should therefore be interpreted differently to adult VEPs.

This thesis reports on several new and innovative instrumentation developments to solve some of the problems of brain activity monitoring, particularly SSVEP (Steady State Visual Evoked Potentials) studies. SSVEP systems generate suitable stimuli and record the resulting brain biopotentials from scalp electrodes. The instrumentation is configured as a 'Neuropsychiatric Workstation', supporting up to 136 scalp electrodes. Operating in the SSVEP mode, the Neuropsychiatric Workstation reported here significantly improves upon the previously reported spatial resolution and accuracy of maps related to the generated stimuli. These maps allows insights to be gained into the cognitive workings of the brain. A significant component of the work reported here covers the development of the multielectrode EEG measurement modules and the associated techniques for minimising interference and cross-talk. The techniques for synchronising recordings from all electrodes with the stimulus, interfacing to a host computer and real-time storage of the very large amounts of data generated to hard disk, are all reported. The SSVEP paradigm uses a sinusoidal-modulated visual stimuli. A novel linearised LED (light emitting diode) head-up display was developed, in addition to more conventional stimuli, such as the alternating checker-board display, all with sinusoidal modulation capability over a range of frequencies. The Neuropsychiatric Workstation described in thesis has been replicated several times and is in regular use at Brain Sciences Institute (BSI) at Swinburne University of Technology, and other collaborative research institutes.