PSEN1 and multiple system atrophy: Cohort 1 (neuropathology cohort): n = 81 (AD n = 34, non-AD n = 47) Cohort 2: n = 699 (MCI n = 178, AD dementia n = 121, non-AD dementia: PD/PDD/MSA, PSP/CBS, bvFTD/PPA, VD n = 99, CU n = 301) - Cohort 3: n = 622 PSEN1 mutation carriers n = 365; age- and sex-matched noncarriers: n = 257