Inclusion Criteria:

For EOAD patients will be recruited from the LEADS trial with the following:

• Age: 40 to 64 years.
• Meets NIA-AA criteria for mild cognitive impairment (MCI) due to AD or probable AD dementia.
• Have a global CDR score of ≤ 1.0.
• Have capacity to provide informed consent (ICF) or has a legal authorized representative or guardian who provides IC.
• Amyloid positive status (PET scan with evidence of elevated amyloid).
• Must have a study partner (informant) who spends a minimum average of 10 hours per week with the participant (e.g., family member, significant other, friend, and caregiver) who is generally aware of the participants' daily activities and can provide information about the participant's cognitive and functional performance. If the participant does not have a study partner who spends 10 face-to-face hours per week, other arrangements for identifying a viable study partner will be granted on a case-by-case basis by the Site PI.
• Not pregnant or lactating. Women must be two years post-menopausal, be surgically sterile, or have a negative pregnancy test prior to each PET scan
• Fluent in English.

Inclusion Criteria:

For Control patients:

• No known medical history of seizures or epilepsy.
• Meets criteria for cognitively normal, based on an absence of significant impairment in cognitive functions or activities of daily living.
• Have a global CDR score = 0.
• Have capacity to provide informed consent.
• Have a Mini-Mental State Exam score between 26-30 (inclusive). Exceptions may be made for participant with less than 8 years of education at the discretion of the Site PI,
• Age between 40-64 years (inclusive) at the time of consent
• Must have a study partner (informant) who spends a minimum average of 10 hours per week with the participant (e.g., family member, significant other, friend, caregiver) who is generally aware of the participants' daily activities and can provide information about the participant's cognitive and functional performance. If the participant does not have a study partner who spends 10 face-to-face hours per week, other arrangements for identifying a viable study partner will be granted on a case-by-case basis by the Site PI.
• Not pregnant or lactating. Women must be two years post-menopausal, be surgically sterile, or have a negative pregnancy test prior to each PET scan.
• Fluent in English.

Exclusion Criteria:

For EOAD and control patients:

• Meets core clinical criteria for non-AD dementia.
• Two or more first degree relatives with a history of EOAD suggestive of autosomal dominant transmission, unless known pathogenic mutations in APP, PSEN1, PSEN2 have been excluded.
• Known mutation in an ADAD gene (APP, PSEN1, PSEN2) or other autosomal dominant genes associated with other neurodegenerative disorders.
• MRI scans with evidence of infection or focal lesions, cortical strokes, multiple lacunes (single lacune is allowable unless it meets criteria for strategic lacune affecting cognition).
• Any significant systemic illness or unstable medical condition, which could lead to difficulty complying with the protocol (at the discretion of the Site PI).
• Medical history of a brain disorder other than the disorder causing dementia except for headache.
• Deemed ineligible by the Site PI for any other reason.