The Neural Correlates of Recollection and Post-Retrieval Monitoring in Younger and Older Adults
Episodic retrieval is not a homogeneous process, but rather involves the engagement of several dissociable cognitive processes. These processes include those specialized for memory functions, such as hippocampally mediated pattern completion processes, as well as generic cognitive control processes linked with activity in the frontal cortex. Thus, age-related decline in episodic memory performance is not consistent across all aspects of retrieval, but dissociable subprocesses contributing to successful retrieval are affected to differing extents. To examine agerelated differences in processes contributing to retrieval, we investigated the neural correlates of recollection and post-retrieval monitoring in samples of younger and older adults using ERP (experiment 1: Ns 20 per group) and fMRI (experiment 2: Ns 28 per group). In experiment 1, we focused on modulation of recollection-related activity (operationalized as subjective report using the RKN procedure) as a function of source accuracy. In experiment 2, we examined how varying the global task demand of an associative recognition task by adding a secondary tone detection task might modulate prefrontal monitoring effects in younger and older adults. Across experiments, we found that both age groups activated a common set of regions supporting memory retrieval (in most cases), but that older adults demonstrated less modulation of recollection- and monitoring-related activity. This finding suggests that a breakdown in the ability to dynamically modulate activity supporting retrieval according to online task demands may be a key factor underlying the decline in memory performance with advancing age.