Expression of game-related and generic knowledge by dementia patients who retain skill at playing dominoes

Patients with dementia who remain skilled at musical performance or playing bridge fail explicit memory tests for information related to their skills, suggesting that implicit memory mediates their preserved skills. To reexamine this issue, 23 dementia patients and 15 elderly controls of comparable domino-playing skill were compared on tests of naming, verbal fluency, and domino knowledge. On an explicit test of domino knowledge, the patients scored well below the elderly controls, performing no better than students who were unfamiliar with the game. But when game-like situations were created with real dominoes, both the skilled controls and the patients with dementia chose optimal moves and verbally explained their choices equally well. On naming and fluency tests, the skilled patients showed no advantage over patients of comparable dementia severity who had no retained skill. In dementia, some complex knowledge seems intact but is accessible only in particular contexts.