In AD, one of the hallmark neurochemical findings is a loss of cholinergic neurons, especially in the basal forebrain, leading to: ↓ ChAT activity ↓ Acetylcholine (ACh) levels ↓ Cognitive function (especially memory and attention) Many AD drugs aim to increase ACh levels by: -Inhibiting acetylcholinesterase (AChE) (which breaks down ACh), e.g., donepezil, rivastigmine.