Abstract
Successful memory encoding depends on the ability to intentionally encode relevant information (via differential encoding) and intentionally forget that which is irrelevant (via inhibition). Both cognitive processes have been shown to decline in aging and are theorized to underlie age-related deficits in the cognitive control of memory. The current study uses the Directed Forgetting paradigm in conjunction with fMRI to investigate age-related differences in both cognitive processes, with the specific aim of elucidating neural evidence supporting these theorized deficits. Results indicate relatively preserved differential encoding, with age differences consistent with previous models of age-related compensation (i.e., increased frontal and bilateral recruitment). Older adults did display noticeable differences in the recruitment of brain regions related to intentional forgetting, specifically exhibiting reduced activity in the right superior prefrontal cortex, a region shown to be critical to inhibitory processing. However, older adults exhibited increased reliance on processing in right inferior parietal lobe associated with successful forgetting. Activity in this region was negatively correlated with activity in the medial temporal lobe, suggesting a shift in the locus of inhibition compared to the frontally mediated inhibition observed in younger adults. Finally, while previous studies found intentional and incidental forgetting to be dissociable in younger adults, this differentiation appears to be reduced in older adults. The current results are the first to provide neural evidence for an age-related reduction in processes that support intentional forgetting.
Highlights
Do older adults have difficulty forgetting? At first glance this may appear to be a nonsensical question, especially when considering the vast literature documenting age-related memory impairments [2,3,4]
This study is the first to examine age differences in the neural correlates that mediate the cognitive control of memory encoding using the Directed Forgetting (DF) paradigm
The data extend previous findings by identifying possible mechanisms by which older adults execute both intentional encoding and intentional forgetting processes, that differ from those observed in younger adults
Summary
Do older adults have difficulty forgetting? At first glance this may appear to be a nonsensical question, especially when considering the vast literature documenting age-related memory impairments [2,3,4]. While the oft-investigated incidental forgetting may be a by-product of poor encoding operations, thereby impairing successful encoding, intentional or goal-directed forgetting is considered to be a strategic process, benefitting memory by reducing interference associated with the processing of irrelevant information. This latter form of forgetting falls under the realm of control operations that influence memory performance. While the majority of behavioral evidence shows an increased rate of incidental forgetting in older adults, the ability to engage cognitive control processes to support intentional forgetting has been shown to diminish with age [1,5,6]. The current study seeks to fill this gap in the literature by elucidating age-related differences in the neural correlates mediating both encoding and inhibition as they pertain to intentional forgetting
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