Differential decline in word generation from phonemic and semantic categories during the course of Alzheimer's disease: Implications for the integrity of semantic memory

The ability to generate words from phonemic (i.e., words beginning with 'F, ' 'A,' and 'S') and semantic (i.e., animals, fruits, and vegetables) catego ries was assessed longitudinally in patients with Alzheimer's disease (AD; N = 59) and normal controls (NC: N = 59). Patients with AD performed worse than NC participants on both tasks at each of 4 annual evaluations and exhi bited greater impairment relative to controls on the semantic-category task than on the phonemic-category task. In addition, the performance of the pa tients with AD declined over time on both tasks, but the rate of decline wa s faster on the semantic-category than on the phonemic-category task. Exami nation of individual responses across the annual evaluations revealed that patients with AD were more consistent than NC participants in failing to ge nerate previously produced semantic-category, but not phonemic-category, it ems in all years following the Ist year in which the item was not produced. These results are consistent with the notion that patients with AD suffer a gradual deterioration of the organization and content of semantic memory as the disease progresses.