Episodic memory deficits in vascular and non vascular mild cognitive impairment

Persons with mild cognitive impairment (MCI) have a cognitive deficit that is insufficient to support a diagnosis of dementia, but have a high risk of developing Alzheimer's disease. Recently, it has been proposed that the presence of cerebrovascular anomalies in addition to MCI could index a prodromal phase of subcortical vascular dementia. The goal of this study was to test the hypothesis that persons with vascular MCI (V-MCI) showed impairment in strategic memory processes whereas persons with non vascular MCI showed a deficit in both strategic and non-strategic memory processes. This was tested in twenty-five persons with V-MCI, twenty-one persons meeting criteria for amnestic MCI and twenty-one matched controls. Three tasks comparing strategic and non-strategic episodic memory processes were used in this study: 1) strategic retrieval was assessed by comparing free recall to recognition; 2) contextual encoding was assessed by comparing item memory to memory for the temporal context of encoding; 3) retroactive interference was measured with an AB/AC paired-associated learning task using either semantically or semantically unrelated word pairs. Both V-MCI and non vascular MCI were impaired relative to controls in free recall and recognition. The two groups also showed lower recall for both item and their temporal context. Finally, both groups were more sensitive than controls to interference in the AB/AC paired-associated paradigm when using semantically related word pairs. Our results indicate pervasive memory impairment in both V-MCI and non vascular MCI. They also indicate that the memory deficit observed in persons with V-MCI is quantitatively and qualitatively similar to what is found in non vascular MCI, and includes a deficit in both strategic and non-strategic memory processes.