Glucose effects on declarative and nondeclarative memory in healthy elderly and young adults

Peripheral glucose ingestion enhances performance on explicit declarative verbal memory tasks in healthy elderly people. In the present experiment, healthy young and elderly adults were administered glucose (50 g) or saccharin followed by tests of declarative verbal memory (free recall and recognition of a word list) and a nondeclarative priming test (word-stem completion). In the elderly, glucose significantly enhanced performance on the declarative but not on the nondeclarative portions of the test. Performance by the young subjects was equivalent in the glucose and saccharin conditions. These findings, that glucose enhances memory for a declarative/explicit but not nondeclarative/implicit task, support the notion that declarative and nondeclarative memory systems are separate functional and anatomic systems.