In Alzheimer's disease, which brain process is reduced in several key regions?

• A. Cerebral blood flow
• B. Glucose metabolism
• C. Oxygen delivery
• D. Neurotransmitter synthesis

Answer: (D)

The main idea is that loss of cholinergic neurons in Alzheimer's disease leads to a drop in neurotransmitter synthesis, especially acetylcholine, across several key brain regions. The nucleus basalis of Meynert normally sends cholinergic signals widely to cortex and hippocampus, supporting learning and memory. When these neurons degenerate, acetylcholine production and release decline, and this deficit tracks with the characteristic memory and cognitive impairments. Although other brain changes occur—such as reduced glucose metabolism and some regional blood flow changes—the most consistent and spreading disruption is neurotransmitter synthesis, reflecting the widespread loss of cholinergic communication that underlies the cognitive symptoms. This is also why cholinesterase inhibitors, which boost acetylcholine levels by slowing its breakdown, can provide symptomatic benefit.