Amnesia and Alzheimer's disease: which neurotransmitter system is responsible?

The cholinergic, noradrenergic, and serotonergic neurotransmitter systems show a consistent pattern of degeneration associated with Alzheimer's disease (AD) and, to a lesser extent, normal aging. The review articles in this section draw a relation between degeneration of one or more of these systems and impairments in learning and memory. Cholinergic hypofunction may underlie the amnesia associated with AD but not that associated with normal aging. The relevance of impaired serotonergic or noradrenergic function to any cognitive impairment associated with aging or AD remains undetermined.