Nature of personal semantic memory: evidence from Alzheimer's disease

Personal semantic memory is factual knowledge about a person's own past. Although personal semantic memory is assumed to have features of both semantic memory and episodic memory, the relationship to episodic memory and to semantic memory have not been well documented. In patients with Alzheimer's disease, episodic memory, semantic memory, and personal semantic memory are all defective. In this study, the hypothesis that defective personal semantic memory is related to both semantic and episodic memory dysfunction was tested in patients with Alzheimer's disease. Functions of episodic, semantic, and personal semantic memory were examined by using the Wechsler Memory Scale-Revised (WMS-R), subtests of the WAIS-R (Information, Vocabulary, Comprehension and Similarities), and the Family Line Test (FLT) in 62 patients who met the NINCDS/ADRDA criteria for probable Alzheimer's disease. Specific effects of episodic and semantic memory on personal semantic memory were examined by using multiple linear regression analysis with the total score of the FLT as the dependent variable and the WMS-R Delayed Recall weighted sum score and the WAIS-R Semantic Memory score (a composite of standardized scores of the four subtests) as the independent variables. Personal semantic memory function was significantly correlated with both the episodic and semantic memory functions, after controlling age, sex, educational attainment, and severity of dementia. This result supports the hypotheses that personal semantic memory has features of both episodic and semantic memory, and that semantic memory is transformed from episodic memory.