The goal of this study is to create a model to predict disease progression in patients with mild cognitive impairments and forms of dementia. To accomplish this, the current study will evaluate different tests including: brain imaging (MRI), body fluid samples (blood and cerebrospinal fluid), skin biopsy, cognitive ability, and behavioural questionnaires. The study team hopes that this information can be used to guide diagnosis and better predict disease progression in patients with mild cognitive impairment and and early dementia.