Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)



First Advisor

William F. Waters


Episodic and semantic memory tasks were administered to patients with Alzheimer's disease (AD) and patients with multi-infarct dementia (MID). The MID group had multi-focal lesions predominantly in the subcortical regions. Episodic memory is recall of events in a particular temporal-spatial context, whereas semantic memory is "knowledge" memory regarding words and their associations. The AD and MID groups were comparable in terms of level of dementia. A control group of healthy elderly subjects was comparable to the dementia groups in regard to age and years of education. The experimental measure of semantic encoding involved presentation of six 14-word lists composed of exemplars drawn from specific semantic categories (e.g., vegetables). Following each list, the subjects were required (1) to rate on a six-point scale the number of exemplars presented for each category, and then (2) to perform a two-alternative, forced-choice recognition (episodic memory) task. Although the MID patients were impaired on the recognition task, this deficit was not as profound as that seen in the AD patients. Contrary to predictions, the AD patients were not markedly insensitive to categorical frequency as compared to the MID patients, and the measure of semantic processing was correlated with episodic memory in the normal control and MID groups but not in the AD group. The results suggest that poor semantic encoding is insufficient to explain the episodic memory deficits in AD.