Phrase repetition in Alzheimer's disease: effect of meaning and length.

Repetition ability depends in part on the intactness of semantic memory. If the conceptual contents of semantic memory are lost as a function of Alzheimer's disease (AD) pathology, meaningfulness of stimuli should have progressively less effect on the ability to repeat as the disease worsens. This study was designed to evaluate the effects of meaningfulness and length of phrasal stimuli on repetition ability in mild and moderate AD patients and normal elderly subjects. Fifty-seven AD patients and 52 normal subjects were given six- and nine-syllable phrases that were meaningful, improbable in meaning, or meaningless. Cross-sectional and longitudinal data analyses were conducted and results failed to confirm a performance pattern consistent with a semantic memory loss theory. Meaningless nine-syllable phrases were those most difficult to repeat for moderate as well as mild AD patients and normal controls.