Age differences in episodic associative learning

Compared with young adults, older adults demonstrate difficulty forming and retrieving episodic memories. One proposed mechanism is that older adults are impaired at binding information into nonoverlapping representations, which is a key function of the hippocampus. The current experiments evaluate age differences in acquiring new memories using a novel episodic associative learning (EAL) task designed to tap hippocampal-dependent binding. The task involved repeated exposure of stimuli pairs and required the formation of new representations of each stimulus pair, as each pair was mapped to a unique keypress response. Notably, individual stimuli appeared in multiple pairs, so pair retrieval was necessary for correct response production. Experiment 1 demonstrated that older adults learned more slowly, and less overall, than young adults on this task. We also found that older adults benefited less than young adults from correct responses and as the number of intervening pairs between repetitions of a pair increased, older adults showed larger decrements in accuracy than young adults. Experiment 2 replicated these findings while minimizing motor demands and providing more practice. We also measured processing speed and spatial reconstruction to determine the involvement of specific cognitive mechanisms in observed age effects. We found that young adults with better spatial reconstruction abilities performed better on the EAL task than young adults with lower abilities and older adults overall. These findings suggest that older adults' lower performance on the task may be partly explained by a decline in hippocampal-supported binding processes and a greater reliance on extrahippocampal learning systems.