Eligibility Criteria:
Inclusion Criteria:
* Males and females aged 40 to 80 years.
* Females have no fertility due to surgery or at least one year after menopause. Otherwise, pregnancy tests should be conducted during screening and every scan visit and should be negative. Males with fertility must use two methods of contraception during the study period and one of them should be barrier contraception. No sperm donation is allowed during the study period and within 90 days after the completion of this study.
* The subject and the subject's legally authorized representative or caregiver should be willing and able to cooperate during the whole research process. According to the judgement of the researcher, there can be a research companion who has regular and sufficient contact with the subjects (spend more than 10 hours a week together). The companion can provide accurate information about the cognitive and functional aspects of the subject, and agrees to accompany the subjects and provide relevant information during the visits. Research companions must be confirmed by researchers that they have sufficient cognitive ability to accurately report subjects' behavior, cognition and function, and can accompany throughout the whole research process with subjects.
* Researchers believe that the subject can complete all the relevant contents of this study.
Exclusion Criteria:
* Current or prior history of any alcohol or drug abuse within the past 3 years (self report).
* Laboratory tests or ECG with clinically significant abnormalities and/or clinically significant unstable medical illness.
* Radiation exposure received from clinical care prior participation in the last year, combined with that from the present study, exceeds an effective dose of 50 mSV.
* Pregnant, lactating or breastfeeding or intention to become pregnant.
* Evidence of clinically significant gastrointestinal, cardiovascular, hepatic, renal, hematological, neoplastic, endocrine, alternative neurological, immunodeficiency (including a positive HIV result), pulmonary, or other disorder or disease. Stable, treated chronic medical conditions like hypertension, hypercholesterolemia, diabetes mellitus, non-metastatic dermatologic or prostatic cancer, etc. are acceptable as long as they do not, in the investigator's opinion, contribute to cognitive dysfunction or limit participation in study procedures.
* In the opinion of the investigator, unsuitable to complete lumbar puncture. For example: history of vertebral deformities, major lumbar back surgery, clinically significant back pain, clinically significant abnormal x-ray, and/or injury or taking blood thinners or lab results that would preclude the subject/patient participation or CSF collection during study.
* MRI exclusion criteria include: findings that may impact cognition such as significant evidence of cerebrovascular disease (more than two lacunar infarcts, any territorial infarct \>1cm3, or deep white matter abnormality corresponding to an overall Fazekas scale of 3, with at least one confluent hyperintense lesion on the FLAIR sequence that is ≥20 mm in any dimension), infectious disease, space-occupying lesion, normal pressure hydrocephalus, CNS trauma, or any other structural abnormality that may impact cognition.
* Veins are not suitable for repeated puncture.
* Implants such as implanted cardiac pacemakers or defibrillators, insulin pumps, cochlear implants, metallic ocular foreign body, implanted neural stimulators, CNS aneurysm clips and other medical implants that have not been certified for MRI, or history of claustrophobia in MRI.
* Daily treatment with anticholinergic antidepressants, typical antipsychotics, or barbiturates, daily treatment with benzodiazepines, opiates, or opioids; treatment with soporifics, stimulants, atypical antipsychotics, centrally acting anticholinergic antihistamines, or centrally acting anticholinergic antispasmodics is prohibited, unless administered intermittently and on a short-term basis and not used within 5 half-lives prior to screening or any neurocognitive assessment.
* Treatment with soporifics, stimulants, atypical antipsychotics, centrally acting anticholinergic antihistamines, or centrally acting anticholinergic antispasmodics is prohibited unless (a) administered daily that initiation or discontinuation of therapy or dose change does not occur within 5 half-lives prior to screening or at any point during the study, or (b) administered intermittently and on a short-term basis and not used within 5 half-lives prior to screening or any neurocognitive assessment.
* Treatment with any therapeutic molecule or treatment that targets Aβ or Tau within 12 months prior to screening.
* Have participated in a clinical trial within 30 days prior to screening or within 5 half-lives since last administration of investigational drug (whichever is greater).
* Researchers consider that other diseases or causes might prevent subjects from completing the entire study.
* Others that do not meet the specific inclusion/exclusion criteria of each part of this study.