Language, Speech and Motor Function in MCI Due to AD and Alzheimer's Disease

The goal of this observational cross-sectional study is to explore the characteristics of language, speech, and motor function in persons with Mild Cognitive Impairment due to Alzheimer's disease ("MCI due to AD") and persons with mild and moderate Alzheimer's disease ("AD"). This study aims to: * Explore motor, speech, and language functions in MCI due to AD and mild and moderate AD. * Combine the characteristics of motor, language, and speech functions to gain more insight into the association of language, speech, and motor changes during MCI due to AD and mild and moderate AD. Researchers will compare the outcomes to an age-matched control group without cognitive impairment. Participants will undergo: * Two motor function tests to assess gait and hand grip strength. * Four language and speech function tests to assess spontaneous speech and verbal fluency..