Inclusion Criteria:    

• The criteria for normal subjects are:
  • No active neurological or psychiatric conditions;
  • No cognitive complaints;
  • Normal neurological exam;
  • No psychoactive medications;
  • If a prior neurological or psychiatric condition was present, they must have returned to normal;
  • They may have chronic medical conditions that do not affect cognition, and are ≥ 18 years old.
• Criteria for patients receiving the diagnosis of MCI have been published (26) and are:
  • Memory complaint documented by patient and collateral source;
  • Normal general cognitive function as determined by measures of general intellectual function and screening instruments-MMSE and Short Test of Mental Status;
  • Normal activities of daily living as documented by history and Record of Independent Living;
  • Not demented by DSM-III-R criteria, and do not meet NINCDS-ADRDA criteria for AD;
  • CDR=0.5 (7,8);
  • Objective memory impairment determined by clinical judgment of the neuropsychologists and neurologists (typically this represents performance at 1.5 SD below age and education matched normals from our community on Auditory Verbal Learning Test and Wechsler Memory Scale – revised, however the diagnosis is not based on rigid cutoffs); and age ≥ 18 years;
  • The diagnosis of dementia is made according to DMS-III-R criteria and AD according to DMS-III-R criteria and AD according to NINCDS/ADRDA criteria. Subjects must be ≥ 18 years of age;
  • The diagnoses of neurodegenerative and demyelinating spectrum diseases are made according to the diagnostic criteria such as McDonald Criteria for MS or Okuda Criteria for radiologically isolated syndrome or diagnostic criteria for neuromyelitis optica spectrum disorders.
• All participants of this study should have had MRI (IRB# 963-97) and PiB PET (IRB# 08-005553) imaging within the last two years so that their PiB status is known.

Exclusion Criteria:   

• Potential study participants will be excluded from enrollment in the study and will be deleted from data analyses if any of the following conditions are present (or become evident):
  • Early onset AD (before age 60);
  • Familial AD due to known genetic mutations;
  • AD with Parkinsonian features;
  • Major depression,;
  • Primary or metastatic intracranial neoplasm;
  • Head trauma;
  • Intra-cerebral hemorrhage;
  • Change in classification from probable AD to any other dementia classification.
• We will exclude individuals with hemispheric stroke; i.e., embolic occlusion of one of the major cortical vessels, as this would confound morphometric analyses.
• Individual with leukoaraiosis or lacunar infarcts, or who develop new lacunar infarcts, after initial enrollment, will not be excluded.
• Medical contraindications to MRI scanning such as a cardiac pacemaker, or the presence of intraocular or intracranial metallic objects, will exclude patients from participation.
• Pregnant women will be excluded from the study.
• Women of Child Bearing Potential (WOCBP) will be given a urine pregnancy test prior to the scan.  Results will be shared with the participant.  If the pregnancy test is positive, the participant will not be able to take part in this study.