Certain learning the symptoms of earliest Alzheimer's disease (AD) involved learning, memory or planning problems. Currently, no medical tests are available to diagnose AD conclusively pre-mortem. However, a large number of Kungsholmen Project studies used cognitive tasks (i.e. visuospatial tasks, language tasks, etc.) attempted to find the preclinical cognitive marks of AD. These studies convincingly demonstrate that the cognitive deficits of AD are possible to detect during a preclinical period spans several years. In addition, numerous neuropathological, electrophysiological and neuroimaging studies supports the hypothesis that the cognitive deficits in AD is related to a possible disconnection between cortical areas. In present article, we describe the present and future researches of early diagnosis method through cognitive and functional imaging testing to help with the clinical diagnosis.