The effects of aging on material-independent and material-dependent neural correlates of contextual binding.

Previous behavioral research suggests that older adults exhibit impairments in source memory across a multitude of stimuli and associated details, possibly due to a deficit in contextual binding. However, it is unclear whether this binding deficit results from alterations in processes that are material-independent, processes that are specific to particular materials, or some combination of the two. We used event-related fMRI to investigate the effect of aging on contextual binding and associated neural activity for words and objects. Behavioral data showed similar age-related deficits in source memory accuracy for both words and objects. Imaging results revealed that young and older adults recruited similar networks of regions in support of contextual binding, independent of material, including the lateral prefrontal cortex (PFC) and hippocampus. Material-dependent binding effects were also present for both groups in ventrolateral prefrontal and parahippocampal cortices for words and objects, respectively. Older adults showed smaller material-independent contextual binding effects in frontal regions, namely the left dorsolateral PFC, and larger binding effects in the hippocampus. Further, age-related declines in object processing effects in extrastriate regions correlated with poorer source accuracy for objects. Collectively, these results suggest that age-related source memory deficits may be primarily due to changes in material-independent contextual binding processes. However, these impairments may be further impacted by impoverished item representations in material-specific processing regions.