Each subject's brain is comprehensively imaged once a year using magnetic resonance imaging (MRI), a technique that employs an electromagnetic field to detect the shape and density of tissue. After analysis, the images will be preserved alongside the subject's clinical data, including genetic information and scores on cognitive tests.

1. First, each image is preprocessed to remove noise introduced by the scanning equipment and to strip out irrelevant details such as the skull.

2. Next, the brain shape and structure are mapped, including the grooves--called sulci, shown in pink--in the folded cortex.

3. Software measures the neuron-rich gray matter in the brain's outer cortex, the underlying fibers of the white matter, and the clear fluid that fills the cavities.

4. A composite is created by averaging the shape and size of all the healthy elderly brains in the ADNI database.

5. Researchers can compare individual subjects' brains to the standard brain.