Data Collection Assessment of cognitive functions The 30-minute protocol of the National Institute of Neurological Diseases and Stroke - Canadian Stroke Network VCI protocols will be used. The 30-minute protocol provides a comprehensive assessment of cognitive functions with emphasis on executive functions, psychomotor speed and memory, which are the cognitive domains predominately impaired in VCI. With support from Health and Health Service Research fund (PI: Vincent CT MOK; Reference Number 06070231), the investigators adapted and validated the 30-minute protocol in a group of Chinese stroke patients and controls and demonstrated good external validity (area under ROC=0.79 [95%CI 0.69-0.89], p<0.001) in differentiating stroke patients from non-stroke controls and concurrent validity with functional measures. In addition to the 30-minute protocol, the digit span tests from the Wechsler Memory Scale will be administered because of the involvement of immediate attention and working memory in VCI.