The effect of semantic relations on the memory deficit associated with Parkinson's disease.

Analysis of a series of verbal memory experiments reveals a systematic performance deficit in subjects with Parkinson's disease, relative to matched normal and right-hemisphere stroke controls, in both recall and recognition tasks. Parkinson patients benefit less from semantic recall cues; they find semantically mediated synonym detections particularly difficult; and they show reduced benefits from the introduction of semantically novel material in a recall task. Their recall is as well organized semantically as that of normal controls, but reduced in amount. Recognition deficits arise principally from increases in false positive responses.