Raymond C. K. Chan

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The association between the 10-repeat allele of the dopamine transporter gene (DAT) and attention deficit hyperactivity disorder (ADHD) is uncertain. This study aimed to conduct a meta-analysis of the association between the 10-repeat allele of a variable number tandem repeat (VNTR) polymorphism in the 3'-untranslated region (UTR) of the DAT1 gene and ADHD.(More)
"Executive functions" is an umbrella term for functions such as planning, working memory, inhibition, mental flexibility, as well as the initiation and monitoring of action. The impairment of executive functions in various clinical groups is a topic of much debate, as are recent attempts to formulate the corresponding intervention and rehabilitation regimes(More)
OBJECTIVE The authors used resting-state functional connectivity MRI to evaluate brain networks in patients with refractory and nonrefractory major depressive disorder. METHOD In a cross-sectional study, 28 patients with refractory major depression, 32 patients with nonrefractory major depression, and 48 healthy comparison subjects underwent scanning(More)
CONTEXT Most of what we know about antipsychotic drug effects is at the receptor level, distal from the neural system effects that mediate their clinical efficacy. Studying cerebral function in antipsychotic-naive patients with schizophrenia before and after pharmacotherapy can enhance understanding of the therapeutic mechanisms of these clinically(More)
BACKGROUND Voxel-based morphometry (VBM) has been widely used in studies of major depressive disorder (MDD) and has provided cumulative evidence of gray matter abnormalities in patients relative to controls. Thus we performed a meta-analysis to integrate the reported studies to determine the consistent gray matter alterations in MDD. METHODS A systematic(More)
BACKGROUND Neurological soft signs (NSS) are associated with schizophrenia and related psychotic disorders. NSS have been conventionally considered as clinical neurological signs without localized brain regions. However, recent brain imaging studies suggest that NSS are partly localizable and may be associated with deficits in specific brain areas. METHOD(More)
Clinical studies indicate that damage to the frontal lobes may lead to a set of symptoms collectively known as 'Dysexecutive syndrome', which is characterized by changes in emotion, personality, motivation, behaviour and cognitive aspects. Factor analytical study using questionnaires measuring dysexecutive problems in everyday life also suggests a(More)
BACKGROUND Spontaneous low-frequency fluctuations (LFF) in the blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) signal have been shown to reflect cerebral spontaneous neural activity, and the present study attempts to explore the functional changes in the regional brain in patients with schizophrenia using the amplitude of(More)
BACKGROUND Neurological soft signs (NSS) are hypothesized as candidate endophenotypes for schizophrenia, but their prevalence and relations with clinical and demographic data are unknown. The authors undertook a quantification (meta-analysis) of the published literature on NSS in patients with schizophrenia and healthy controls. A systematic search was(More)
BACKGROUND Many studies using diffusion tensor imaging (DTI) have demonstrated impaired white matter integrity in patients with major depressive disorder (MDD), with significant results found in diverse brain regions. We sought to identify whether there are consistent changes of regional white matter integrity in patients with MDD, as shown by decreased(More)