Amnestic disorders. Pathophysiology and patterns of memory dysfunction.

A wide variety of conditions seen in medical practice can produce memory impairment (amnesia). Normal aging, depression, and anxiety are commonly associated with memory difficulties, as are many neurologic conditions. Systemic illnesses can impair memory by injuring vulnerable limbic regions sensitive to hypoxia or hypoglycemia. Commonly used over-the-counter and prescription medications can likewise cause amnesia. These conditions disrupt memory in characteristic ways. Recent studies suggest that immediate, recent, and remote memory functions have different neuroanatomic substrates, as do the processes of registration, retention, and retrieval. New classifications have emerged to explain the evidence for multiple memory subsystems. The neuropharmacology of memory now includes several peptides in addition to cholinergic and noradrenergic pathways. Critical limbic regions have been discovered that mediate memory consolidation, and neuronal mechanisms such as long-term potentiation are being implicated in the unique capacity of these areas to permit new learning to take place.