to AD, another group has mild memory problems known as mild cognitive impairment (MCI), and the final control group consists of healthy elderly participants. ADNI-1 initially enrolled 200 healthy elderly, 400 participants with MCI, and 200 participants with AD. ADNI-GO, ADNI-2 and ADNI -3 added additional participants to augment the cohort, for final cohort size of over 1000 participants (Table 1). Table 1: Testing of participants ADNI uses a variety of techniques to study its participants. After obtaining informed consent, participants undergo a series of initial tests that are repeated at intervals over subsequent years (Table 2): a clinical evaluation to assess overall health and relevant history such as education neuropsychological tests to assess aspects of brain function affected by AD such as memory, executive function, and the ability to perform activities of daily living. genetic testing for the major AD genetic risk factor, APOE ε4, the gene for a form of apolipoprotein E, and other studies lumbar puncture to collect cerebrospinal fluid (CSF) which is tested for the AD biomarkers β-amyloid, the main component of amyloid plaques, and tau protein, which forms Alzheimer's brain tau tangles. Magnetic resonance imaging (MRI) scans to assess brain structure, connectivity, and the extent of white matter disease Positron emission tomography (PET) scans to assess how well the brain uses glucose, and the extent of amyloid plaques and tau tangles. Neuropathological examination if a participant dies and has consented to autopsy. This definitively diagnoses AD by identifying amyloid plaques and tau tangles, and also notes other common comorbidities. Table 2 Data sharing One defining characteristic of ADNI is the commitment by all participating research groups to share ownership of the data prior to the completion of the research and by collaborators to forgo any patent opportunities. This has been described by the head of the ADNI and data publications committee as "a radical experiment in open data access". All data generated by the ADNI study are entered into the data archive hosted at the Laboratory of NeuroImaging (LONI) at the University of Southern California. In 2013, whole genome sequencing data for the entire ADNI cohort were added to the LONI database. Qualified researchers worldwide can access image and clinical data sets that have undergone quality control procedures. To date nearly 1800 applications for data use have been received from investigators in multiple disciplines, and over 7 million brain scan images and clinical data sets