Imaging Tau in Alzheimer's Disease and Normal Aging

This study is being done to determine the relationship between tau tangles and cognitive
impairment in elderly subjects with different clinical and biomarker profiles of Alzheimer's
disease (AD). Subjects will undergo screen that includes neuropsychological testing and brain
MRI. This study uses a special type of scan called a PET scan to take pictures of the brain.
During the PET scan, a special radioactive dye called 18F-THK-5351 is injected into the body.
18F-THK-5351 sticks to abnormal tangles made of the protein tau. Subjects will have the
option to have lumbar puncture performed to measure CSF concentrations of biomarkers.

Inclusion Criteria:

1. Age 50 and older.

2. Meet criteria for either a) amnestic mild cognitive impairment (single or mixed
domain) or mild Alzheimer's disease, or b) have no cognitive impairment, based on
history, exam, neuropsychological testing, and consensus diagnosis. MCI and mild AD
patients must have Clinical Dementia Rating scale score of 0.5 or 1. Unimpaired
subjects must have Clinical Dementia Rating scale score of 0.

3. Subjects unable to provide informed consent must have a surrogate decision maker.

4. Written and oral fluency in English or Spanish.

5. Able to participate in all scheduled evaluations and to complete all required tests
and procedures.

6. In the opinion of the investigator, the subject must be considered likely to comply
with the study protocol and to have a high probability of completing the study.

Exclusion Criteria:

1. Past or present history of certain brain disorders other than MCI or AD.

2. Certain significant medical conditions, which make study procedures of the current
study unsafe. Such serious medical conditions include uncontrolled epilepsy and
multiple serious injuries.

3. Contraindication to MRI scanning.

4. Conditions precluding entry into the scanners (e.g. morbid obesity, claustrophobia,
etc.).

5. History of kidney disease or presence of impaired kidney function based on laboratory
tests at the screening visit.

6. History of liver disease or presence of impaired liver function based on laboratory
tests at the screening visit.

7. Participation in the last year in a clinical trial for a disease-modifying drug for
AD.

8. Inability to have a catheter in subject's vein for the injection of radioligand.

9. Inability to have blood drawn from subject's veins.