Age-related differences in brain activity during true and false memory retrieval

Abstract

Compared to young adults, older adults show not only a reduction in true memories but also an increase in false memories. We investigated the neural bases of these age effects using functional magnetic resonance imaging and a false memory task that resembles the Deese-Roediger-McDermott (DRM) paradigm. Young and older participants were scanned during a word recognition task that included studied words and new words that were strongly associated with studied words (critical lures). During correct recognition of studied words (true memory), older adults showed weaker activity than young adults in the hippocampus but stronger activity than young adults in the retrosplenial cortex. The hippocampal reduction is consistent with age-related deficits in recollection, whereas the retrosplenial increase suggests compensatory recruitment of alternative recollection-related regions. During incorrect recognition of critical lures (false memory), older adults displayed stronger activity than young adults in the left lateral temporal cortex, a region involved in semantic processing and semantic gist. Taken together, the results suggest that older adults' deficits in true memories reflect a decline in recollection processes mediated by the hippocampus, whereas their increased tendency to have false memories reflects their reliance on semantic gist mediated by the lateral temporal cortex.

Figure 1

During encoding, participants were presented with short DRM lists. At retrieval, they viewed words from the list (targets), new words from different, unpresented categories (unrelated lures), and new words from presented categories (related lures). Participants were asked to make a recognition with confidence decision for each word presented at retrieval.

Figure 2

Age-related differences in TRA. The hippocampus (A) shows an age-related decrease in true retrieval, whereas the retrosplenial cortex (B) shows an age-related increase in true activity. Bar graphs represent functional activation (and standard error) associated with high- and low-confidence true memory for both age groups (see Table 4 for coordinates).

Figure 3

Negative correlation between activity associated with high-confidence true memory in the hippocampus and in the retrosplenial cortex in older adults (A) across participants and (B) across trials (in one randomly chosen participant).

Figure 4

Age-related increase in false retrieval in the left middle temporal gyrus. Bar graphs represent functional activation (and standard error) associated with high- and low-confidence false memories for both age groups (see Table 4 for coordinates).