Influence of controlled encoding and retrieval facilitation on memory performance of patients with subcortical ischemic vascular dementia and Alzheimer’s disease

Patients with subcortical ischemic vascular dementia (SIVD) perform better than Alzheimer's disease patients (AD) on the Free and Cued Recall Selective Reminding test (FCSRT). In this test, SIVD are able to overcome their strategic retrieval deficit, whereas AD patients, whose memory impairment is due to a hippocampal storage deficit, are not. However, the FCSRT does not assess the advantage passing from free to assisted learning, which is expected to be different in frontal and hippocampal damage. We compared SIVD, AD and healthy subjects on the free recall of a 15-word list not assisted at encoding and on the free and cued recall of the FCRST. Indexes of Encoding, Cueing and Total (measuring the advantage passing from the 15-word list free recall to the free and cued recall of the FCRST) were computed. The two groups performed comparably poorly on the free recall of the 15-word list, but SIVD outperformed AD patients in the free and cued recall of the FCSRT and took greater advantage than AD patients on both learning and recall when passing from the unassisted to the assisted paradigms. All indexes significantly predicted diagnostic group membership, but the Total Index showed the larger classification accuracy with 80% of AD and 71% of SIVD correctly classified. These results confirm that the FCRST is able to differentiate AD and SIVD patients with a good level of accuracy. However, the evaluation of memory performance variation as a function of support to encoding provides additional data able to increase diagnostic reliability.