Recollection and familiarity in amnestic mild cognitive impairment: a global decline in recognition memory

Abstract

Despite memory failures being a central feature of amnestic mild cognitive impairment (a-MCI), there is limited research into the nature of the memory impairment associated with this condition. A further understanding could lead to refinement of criteria needed to qualify for this designation and aid in prediction of who will progress to development of clinical Alzheimer's disease. Dual process models posit that recognition memory is supported by the dissociable processes of recollection and familiarity. The present study sought to evaluate recognition memory in a-MCI in the framework of the dual process model. Patients with a-MCI and age- and education-matched controls were tested on three memory paradigms. Two paradigms were modifications of the process-dissociation procedure in which recollection required either memory of word-pair associations (associative) or the font color of words at study (featural). A final paradigm utilized the task-dissociation methodology comparing performance for item and visual spatial source memory. All three tasks revealed that familiarity was impaired to at least the same extent as recollection. As familiarity is thought to be spared in normal aging, its measurement may provide a relatively specific marker for the early pathological changes of Alzheimer's disease.

Figure 1. Experimental paradigms

Schemas for the (a) associative process-dissociation procedure task, (b) the item versus visual spatial source task, and (c) the featural process-dissociation task are displayed. For the two process-dissociation tasks, only included items are to be given an old response. In the study phase of the featural task, the outlined and grey fonts represent green and red words on the actual task, respectively. For the displayed version, subjects are asked to only call words studied in red “old.”

Figure 2. Measures of recollection and familiarity for the three experimental paradigms

For experiment 2, the recollection measure is derived from the proportion of correct visual spatial source judgments over the number of correctly recognized items (this calculation is perhaps closest to the independence assumption used for calculation of recollection with the other two experimental paradigms). The familiarity measure for experiment 2 is based on item memory performance, which is not process pure, but presented here given its greater dependence on familiarity relative to the source memory task.