HKU Scholars Hub

    The neurobiological and cognitive processes underpinning stress-induced impact on decision-making

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    Research evidence shows that acute stress and the effect of cortisol could alter decision-making performance, with individual cortisol responsiveness as mediating factor. Men have been consistently reported to make disadvantageous decisions due to their higher risk-taking or reward-seeking behaviours, while women show the reverse trend. However, a certain degree of risk-taking is necessary in many important decisions in real life, yet relatively few research studies have used a decision-making task that requires a risk-taking tendency for advantageous outcomes (i.e. risk-seeking decision-making). In addition, the specific mechanisms underlying the cortisol effect on this type of decision-making are not fully known. Study 1 was an experimental study using the Balloon Analogue Risk Task (BART) as the risk-seeking decision-making task. The effect of cortisol responsiveness and gender on decision-making and its underlying cognitive components was examined in a healthy university sample (42 men and 42 women). Stress was induced by the Trier Social Stress Test (TSST) in the experimental condition. Three cognitive tasks (Tower of London test, Stroop test, and a masked emotional Stroop task) and the BART were then administered. The data showed that when under stress, the men had better risk-seeking decision-making performance than the women. The interaction between gender and cortisol responsiveness was not significant. Descriptively, the male cortisol responders tended to be more risk-taking while the female responders showed less consistent risk-taking behaviours. The relationship between risk-taking behaviours and cortisol reactivity was negative among the male cortisol responders, while the results for the female responders showed a quadratic relationship with risk-taking behaviours that increased with cortisol reactivity but then declined. Study 2 extended the experimental design of Study 1 to 16 male law enforcement officers and used a simulated crisis intervention as an effective stress induction. The cortisol responders appeared to be more risk-avoidance when compared with the non-responders. Cortisol reactivity in the police officers was associated with the personality tendencies of lower openness, higher sensitivity to somatic symptoms, and higher interpersonal suspiciousness, which might have been shaped by the law enforcement culture and altered their decision-making behaviours when under stress. Study 3 was a small exploratory study to investigate cortisol responsiveness and risk-seeking decision-making in a subgroup of the sample from Study 1 (17 men and 24 women) with different types of psychopathic personality traits as classified by the factor scores of the Psychopathic Personality Inventory – Revised (PPI-R). Compared with those with low psychopathic traits, the participants with high traits in global psychopathic personality, Fearless Dominance (FD), and Self-centred Impulsivity (SCI) generally displayed the tendency of increased cortisol reactivity to the TSST and more risk-taking behaviours in decision-making. However, the individuals with high Cold-heartedness (CH) traits appeared to show the profile of a “successful psychopath,” namely the lack of a risk-taking tendency and better executive planning ability. The cognitive components underlying the risk-seeking decision-making could not be directly identified from the data, yet the possible underlying mechanisms in cortisol responders and non-responders implied from the present findings were discussed.published_or_final_versionPsychologyDoctoralDoctor of Philosoph

    Bamboo in principle : Ke Jiusi's (1290-1349) paintings and knowledge in the Yuan dynasty (1271-1368)

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    This thesis addresses the historical and cultural context of bamboo painting by Ke Jiusi 柯九思 (1290-1349), a famous ink bamboo painter and an art connoisseur at the Yuan (1271-1368) Mongol court. By reassessing the historical significance of bamboo, the status of bamboo painters, and the function of bamboo painting in the Yuan, this thesis seeks to reclaim alternative meanings for bamboo painting. Traditional scholarship considers bamboo painting as an art with lofty-minded associations for artists to articulate independence from the court. As my research addresses, artists who painted bamboo collaborated with the Mongol imperium. A review indicates that government administrators and emperors valued the materiality and cultural meanings of bamboo. A metaphor for virtue, bamboo represented rulers, aristocrats, scholar officials and military leaders. By the Yuan, bamboo was an established painting subject that experienced stylistical developments and elaborations, that contemporary viewers referred as different schools (pai 派). Combining textural documents and visual materials, this thesis examines the changing meanings of the Huzhou School – a style associated with Wen Tong 文同 (1018-1079) and Li Kan 李衎 (1245-1320). In my interpretation Ke Jiusi sought to promote and perpetuate the new meaning of the Huzhou school through his bamboo painting. Ke Jiusi responded to and shaped newly developing roles for bamboo in the Yuan. Bamboo became a vehicle for the display of knowledge of the li 理 (universal principle) in Neo-Confucian teachings. Such associations between bamboo and Neo-Confucianist ideas generated shifts in the meanings of bamboo painting and of li. By the Yuan, li in painting stands for the artists’ ability to observe and represent the subject in variations of forms and conditions with descriptive details. The Mongol court had decreed Zhu Xi 朱熹 (1130-1200) as providing the authoritative interpretations of the Confucian Classics. Consequently artists such as Li Kan and Ke Jiusi applied this philosophy to attaining li through gewu 格物 (investigating things) in bamboo painting. They revitalized the Wen Tong style of naturalistic bamboo. Mongol rulers rewarded these bamboo painters with court positions and celebrated their style as representative of the genuine scholar-officials (zhen shidafu 真士大夫). This fostered a competitive environment among bamboo painters of different styles and we see an increase in artists who were interested in painting the subject bamboo. Rather than continuing with the present understanding of Chinese literati, artists, and scholar-officials in conflict with the Mongol court, the thesis seeks to regard bamboo painting as an instance, possibly one of many, in which the Mongol imperium and cultural elites collaborated. By analyzing Ke Jiusi’s Bamboo Suite (Zhupu 竹譜), I argue that Ke depicted bamboo in relation to its changing environmental conditions, developing his distinctive style of ink bamboo painting. Through these new formal arrangements, Ke Jiusi positioned himself as the legitimate successor of Wen Tong, and advanced his descriptive and meticulous brushwork as genuinely scholarly.published_or_final_versionFine ArtsDoctoralDoctor of Philosoph

    A dox-terminable cell-encapsulating device for intravitreal drug delivery

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    The Symposium was jointly organized by the Hong Kong Ophthalmological Society and the College of Ophthalmologists of Hong KongPoster PresentationObjectives: Encapsulated-cell therapy presents a way of localized and sustained drug delivery to the posterior eye. An injectable collagen-alginate drug delivery platform was designed with promising result previously. Now, a Tet-On inducible apoptotic control is further introduced for safety. Methods: GDNF-expression HEK293 cells were transfected with pcDNATM6/TR and recombinant Caspase 8 plasmid. Cell death upon Dox exposure in cell-encapsulating collagen-alginate gel was assayed by MTS. Biocompatibility and stability of the gel system as well as its encapsulated cell viability were evaluated on 7 and 28 days post intravitreal injection by microscopy. Results & conclusion: Complete cell death via caspase-mediated apoptosis was achievable within 72 hours of 0-2ug/ml Dox induction. Intravitreally injected device displayed good biocompatibility, mechanical stability and encapsulated cell viability after prolonged implantation in RCS rat eyes. We have successfully established a Dox-terminable cell-encapsulating intravitreal drug delivery device with good biocompatibility and stability after implantation in rats

    Selective astrocytic endothelin-1 over-expression contributes to dementia associated with ischemic stroke by exaggerating astrocyte-derived amyloid secretion.

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    Endothelin-1 (ET-1) is synthesized by endothelial cells and astrocytes in stroke and in brains of Alzheimer’s disease patients. Our transgenic mice with ET-1 overexpression in the endothelial cells (TET-1) showed more severe blood–brain barrier (BBB) breakdown, neuronal apoptosis, and glial reactivity after 2-hour transient middle cerebral artery occlusion (tMCAO) with 22-hour reperfusion and more severe cognitive deficits after 30 minutes tMCAO with 5 months reperfusion. However, the role of astrocytic ET-1 in contributing to poststroke cognitive deficits after tMCAO is largely unknown. Therefore, GET-1 mice were challenged with tMCAO to determine its effect on neurologic and cognitive deficit. The GET-1 mice transiently displayed a sensorimotor deficit after reperfusion that recovered shortly, then more severe deficit in spatial learning and memory was observed at 3 months after ischemia compared with that of the controls. Upregulation of TNF-α, cleaved caspase-3, and Thioflavin-S-positive aggregates was observed in the ipsilateral hemispheres of the GET-1 brains as early as 3 days after ischemia. In an in vitro study, ET-1 overexpressing astrocytic cells showed amyloid secretion after hypoxia/ischemia insult, which activated endothelin A (ETA) and endothelin B (ETB) receptors in a PI3K/AKT-dependent manner, suggesting role of astrocytic ET-1 in dementia associated with stroke by astrocytederived amyloid production

    On ergative case in Himalayan languages

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    We discuss variation in the appearance of the ‘ergative’ case in Bumthang, a Bodic language of central Bhutan (described in van Driem 1995). In this paper, we report on fieldwork from the variety spoken in Ura, in the south-east of the language’s range. In particular, we focus on the ergative case and suggested analysis for how to determine ergative case usage as outlined in Donohue & Donohue 2016. In the context of other Himalayan languages, we discuss how the findings bear on other Himalayan languages and situate the analysis in the literature discussing other languages that show variability in the use of the ergative case, not uncommon in the Himalayas (e.g. Chelliah & Hyslop 2011). We discuss how the variation in ergative marking varies due to information structure differences (topic, or anti-topic), as well as differences in tense/aspect, lexical aspect, and animacy. While each of these factors have been shown to be important in determining the use of ergative case in other languages described as showing split ergativity, Bumthang shows us that at least in some languages, all these factors are important in understanding the use of the ergative case marker. We discuss these results in a typological context with a focus on south Asian languages
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