In Parkinson's disease acetylcholine activity is increased; in Alzheimer's disease it is decreased.

• A. Increased in both
• B. Increased in Parkinson's and decreased in Alzheimer's
• C. Decreased in Parkinson's and increased in Alzheimer's
• D. Decreased in both

Answer: (B)

Neurotransmitter balance in movement circuits is governed by dopamine and acetylcholine. In Parkinson’s disease, loss of dopamine reduces its inhibitory control over acetylcholine release in the striatum, so acetylcholine activity becomes relatively higher, contributing to motor symptoms like tremor and rigidity. In Alzheimer's disease, degeneration of basal forebrain cholinergic neurons leads to a marked decrease in acetylcholine, which underlies memory and cognitive impairments. Because the changes occur in opposite directions for these two diseases, the statement that acetylcholine activity is increased in Parkinson's and decreased in Alzheimer's best fits the neurochemical patterns seen in each condition. This also explains why treatments target acetylcholine differently: anticholinergic drugs can help manage Parkinsonian symptoms, while cholinesterase inhibitors are used to support cognition in Alzheimer's.