Neurocognitive mechanisms of guided item and associative encoding in young and older adults

A hallmark of aging is a decline in episodic memory that is especially pronounced for memory for associations. To examine the neurocognitive mechanisms, young and older adults completed an item encoding task involving a semantic judgment on individual objects and an associative encoding task involving a judgment whether one of two objects could fit into the other, while their EEG was recorded. Item and associative recognition were equally reduced in older adults, unexpectedly yielding no disproportionate age-related associative deficit. A behavioral follow-up experiment did reveal an associative deficit when item and associative memory were both tested for the stimuli encoded in an easier version of the associative task, although this effect tended to be smaller than the deficit in an interactive imagery task. The behavioral and ERP results together suggest that in the item task, older adults failed to bind together perceptual object features, leading to low item memory performance. In the association task, both age groups engaged shallow, perceptual encoding processes, which appeared to be less efficient in older adults. These results suggest that the age-related associative deficit is modulated by the extent to which both item and associative memory depend on low-level feature binding and higher-level strategic processes.