Memory: Clinical Disorders

Althoughmemory is usually robust and accurate, different disease processes can disrupt memory and cause either distortions or outright failure. The goal of this article is to provide an overview of the six basic memory systems, their relevant neuroanatomy (Figure 1) and the clinical disorders that disrupt them (Table 1). By ‘memory system’, wemean a way in which the brain processes information that is available for use at a later time, with or without conscious awareness (Schacter and Tulving, 1994). These memory systems can, at least in theory, be dissociated from one another. As we will see, several disease states primarily affect onememory system, andmany others affectmultiple systems. Memory systems can be divided into those that are declarative and those that are nondeclarative. Declarative or explicit memory is memory for events that can be consciously recalled. Nondeclarative or implicit memory, by comparison, is memory that is expressed as a change in behaviour, and is often unconscious.