“…In patients dying of nonneurological causes, the activity of choline acetyltransferase (CAT), an enzyme that catalyzes the synthesis of acetylcholine, decreases with age for patients between 20 and 50 (McGeer & McGeer, 1976). After age 60 there is no significant correlation between age and CAT activity, but there is a negative correlation between CAT activity and the degree of neurohistological change characteristic of Alzheimer's disease; specifically, the number of senile plaques and the number of neurofibrillary tangles are inversely related to CAT activity (Bowen et al, 1976;Bowen, Spillane, Curzon, Meier-Ruge, White, Goodhardt, Iwangoff, & Davison, 1979). When they are compared with nondemented, age-matched controls, Alzheimer's patients are found to have significantly lower CAT activity (Bowen et al, 1979;Perry, Tomlinson, Blessed, Bergman, Gibson, & Perry, 1978).…”