Thesis (M. Med. Sc.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 43-47).

Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2002. / Includes bibliographical references (leaves 180-202). Also available in electronic version. Access restricted to campus users.

Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2009. / Full text also available online. Scroll down for electronic link.

Thesis (Ph. D.)--Ohio State University, 2003. / Title from first page of PDF file. Document formatted into pages; contains xiii, 184 p.; also includes graphics (some col.). Includes abstract and vita. Advisor: Andrej Rotter, Dept. of Biochemistry. Includes bibliographical references (p. 158-184).

Thesis (M.D.)--University of Hong Kong, 1980.

published_or_final_version / Paediatrics and Adolescent Medicine / Doctoral / Doctor of Philosophy

Here we examined hemispheric differences in conscious and nonconscious perception using a masked priming paradigm. In Experiment 1, participants judged the direction of a grey target arrow (either left- or right-pointing), which was preceded by a grey prime arrow in either the left visual field (LVF)/right hemisphere (RH) or the right visual field (RVF)/left hemisphere (LH). The prime was either masked or unmasked. Participants reported unaware of the prime in the masked condition. We found a significant congruency effect (i.e., a faster response when the prime and target directions were congruent than when they were incongruent) when the prime was presented in the LVF/RH but not the RVF/LH in the masked (subliminal) condition. In contrast, in the unmasked (supraliminal) condition, the RVF prime had a stronger congruency effect than the LVF prime. In Experiment 2, a backward mask was used in all trials and the prime duration was manipulated to create subliminal and supraliminal conditions. In the subliminal condition, LVF/RH primes but not RVF/LH primes generated a congruency effect, whereas in the supraliminal condition, RVF/LH primes had a bigger congruency effect than LVF/RH primes. These qualitatively different hemispheric asymmetry effects in Experiment 1 and 2 suggest that nonconscious and conscious perception may involve different underlying mechanisms. In Experiment 3, color stimuli instead of grayscale stimuli were used. Neither the congruency effect nor the LVF/RH advantage was found in the subliminal condition, while a similar RVF/LH advantage in the congruency effect was found in the supraliminal condition. This result suggests that parvocellular input does not support the subliminal priming effect in the LVF/RH. Taking together, our results revealed a dissociation between the mechanisms underlying nonconscious and conscious processing, and this dissociation may be due to the dominant role of the magnocellular pathway in nonconscious vision. / published_or_final_version / Psychology / Master / Master of Philosophy

Ischaemic stroke rates are expected to rise significantly in the next decades due to an aging population. This increases the demand for new stroke biomarkers for early detection of patients at risk and new targets for treatment. It has been hypothesized that epigenetics may be important in the aetiology of stroke. The study consisted of three types of investigation: analysis of candidate gene polymorphism, candidate gene methylation analysis and epigenome-wide methylation analysis (EWAS) of pooled stroke and control samples. The stroke types studied were large vessel disease (LVD), small vessel disease (SVD) and cardioembolic stroke (CE). DNA from peripheral blood samples was used for EWAS and methylation analysis. Significant increases in rare allele frequency were observed in the EHMT2 and DNMT3B genes for all stroke cases; MBD2, DNMT3B and DNMT3L polymorphisms were associated with LVD. IL10, SOD3, LINE1 and PITX2 were significantly hypomethylated in LVD. IL10 and ALOX15 were hypomethylated in CE compared to controls. Methylation levels of following genes were associated with age (LINE1, IL10, MTHFR, TNFα, and PITX2), gender (SOD3 and LINE1), total cholesterol level (SOD3) and systolic blood pressure (IL10). HDAC9 genetic polymorphism was associated with the MTHFR methylation level. A distinctive methylation pattern for each stroke subtype was found by EWAS. The CE pool was hypomethylated at genome, chromosome and gene level, while LVD and SVD pools had regions with higher and lower methylation levels compared to the controls. GNAS was identified as new candidate gene by EWAS. The results suggested that genetic polymorphism and DNA methylation levels of candidate genes were associated with ischaemic stroke. Stroke subtypes had distinct methylation profiles suggesting differences in underlying aetiology. Variations in methylation levels detected in this study could lead to identification of specific biomarkers. Replication on a large number of subjects is required before final conclusions can be drawn.

published_or_final_version / abstract / toc / Clinical Psychology / Master / Master of Social Sciences

A persistent unanswered question in cognitive neuroscience has been what are the neural origins of human brain lateralization? Language is strongly lateralized to the left-hemisphere, however, lateralization varies with language experience. Bilinguals demonstrate a greater extent and variability of right-hemisphere involvement for language relative to monolinguals. Here, bilingualism is used as a lens into the conditions that drive brain lateralization. Why does bilingual language processing yields more robust bilateral neural activation relative to monolingual language processing? Neural activation and functional connectivity were measured to test hypotheses about the temporal dynamics of hemispheric recruitment during language processing in monolingual and bilingual children with varying ages of first bilingual language exposure. Hypothesis (1), The human brain is strongly left-hemisphere lateralized for language, but, when faced with the demands of two languages, additional right-hemisphere resources are recruited. Hypothesis (2), The human brain has the potential for enhanced dual hemispheric language processing that can be either potentiated or not based on early life bilingual versus monolingual language experience. If dual language experience places increased cognitive demands on the bilingual brain requiring additional right-hemisphere resources, asynchronous neural activation in left and right hemispheres was predicted. If dual language experience potentiates dual hemispheric language processing, synchronous neural activation in left and right hemispheres was predicted. Furthermore, only early-exposed bilinguals but not later-exposed bilinguals or monolinguals, would show synchronous neural activation across the hemispheres. Early experience with one language (monolinguals) or two languages at different times during a child's development (early-exposed bilinguals, later-exposed bilinguals) revealed differences in the time-course of activation across the two hemispheres' language areas, supporting Hypothesis (2). Monolinguals and later-exposed bilinguals showed asynchronous activation between the hemispheres. Early-exposed bilinguals showed synchronous activation between the hemispheres. The results provide a new view on how different experiences can drive lateralization in development and reveal the neural basis of bilateral activation in the bilingual brain. Synchronous temporal accessing of the hemispheres in bilinguals suggests early life bilingual language experience may support more equal and efficient hemispheric involvement, and, in turn, constitute the brain-based mechanism that makes possible the widely observed linguistic and cognitive advantages in young bilinguals.