| 
      Note: cerebrospinal fluid amyloid beta peptide 42 (AB42), fractional anisotropy (FA), and radial diffusivity (RD)
        |  | N | Mean (SD) |  
        | Age | 186 | 62.0 (9.5) |  
        | CSF AB42 | 150 | 636.2 (215.9) |  
        | Education | 171 | 16.0 (2.6) |  
        | Mini–mental state    examination (MMSE) | 171 | 29.3 (1) |  
        | Whole brain volume | 154 | 0.80 (0.02) |  
        | Pittsburgh Compound B (PIB) | 152 | 0.06 (0.16) |  
        | FA corpus callosum genu    region | 165 | 0.84 (0.09) |  
        | RD corpus callosum genu    region | 165 | 0.24 (0.15) |  |