The distinctiveness of neural information representation is crucial for successful
memory performance but declines with advancing age. Computational models implicate
age-related neural dedifferentiation on the level of item representations, but previous
studies mostly focused on age differences of categorical information representation
in higher-order visual regions. In an age-comparative fMRI study, we combined univariate
analyses and whole-brain searchlight pattern similarity analyses to elucidate age
differences in neural distinctiveness at both category and item levels and their relation
to memory. Thirty-five younger (18-27 years old) and 32 older (67-75 years old) women
and men incidentally encoded images of faces and houses, followed by an old/new recognition
memory task. During encoding, age-related neural dedifferentiation was shown as reduced
category-selective processing in ventral visual cortex and impoverished item specificity
in occipital regions. Importantly, successful subsequent memory performance built
on high item stability, that is, high representational similarity between initial
and repeated presentation of an item, which was greater in younger than older adults.
Overall, we found that differences in representational distinctiveness coexist across
representational levels and contribute to interindividual and intraindividual variability
in memory success, with item specificity being the strongest contributor. Our results
close an important gap in the literature, showing that older adults' neural representation
of item-specific information in addition to categorical information is reduced compared
with younger adults.
