Unitization improves source memory in older adults: An event-related potential study

Aging-related decline in episodic memory, particularly in associative memory, is attributed to an impaired recollection of the specific details of a study episode. Fortunately, familiarity is relatively preserved in older adults. Previous studies have indicated that unitization is a specialized form of learning that increases the contribution of familiarity to associative retrieval. Here we examined whether older adults' associative memory could be improved when employing an encoding strategy that encouraged unitization. Young and older adults encoded items and background colors either in a unitized condition (i.e., by imagining the color as an internal feature of the item) or in a non-unitized condition (i.e., by imagining the color as a contextual feature of the item). The participants then performed a source recognition test. The effects of unitization on the neural correlates of familiarity were measured by event-related potentials (ERPs). The age differences in source memory performance were lower in the unitized condition than in the non-unitized condition. The older adults only demonstrated neural correlates of familiarity-based source recognition in the unitized condition. These findings suggest that a unitized encoding strategy could improve source memory performance in older adults by enhancing the involvement of familiarity in source recognition.