Associative working memory and subsequent episodic memory in Alzheimer's disease.

Recent studies indicate deficits in associative working memory in patients with medial-temporal lobe amnesia. However, it is unclear whether these deficits reflect working memory processing or are due to hippocampally mediated long-term memory impairment. We investigated associative working memory in relation to subsequent episodic memory formation in patients with early Alzheimer's disease to examine whether these findings reflect deficits in long-term encoding rather than 'pure' working memory processing. Nineteen patients with Alzheimer's disease and 21 controls performed a working memory task in which objects had to be searched at different locations. The subsequent episodic memory test required participants to reposition objects to their original locations. Patients with Alzheimer's disease were impaired on associative working memory and subsequent episodic memory, but they performed above chance at high-load episodic memory trials. This suggests that when working memory capacity is exceeded, long-term memory compensates.