'Royal College of Obstetricians & Gynaecologists (RCOG)'
Abstract
Older adults and particularly those at risk for developing dementia typically show a
decline in episodic memory performance, which has been associated with altered
memory network activity detectable via functional magnetic resonance imaging
(fMRI). To quantify the degree of these alterations, a score has been developed as a
putative imaging biomarker for successful aging in memory for older adults (Functional Activity Deviations during Encoding, FADE; Düzel et al., Hippocampus, 2011; 21:
803–814). Here, we introduce and validate a more comprehensive version of the
FADE score, termed FADE-SAME (Similarity of Activations during Memory Encoding),
which differs from the original FADE score by considering not only activations but
also deactivations in fMRI contrasts of stimulus novelty and successful encoding, and
by taking into account the variance of young adults' activations. We computed both
scores for novelty and subsequent memory contrasts in a cohort of 217 healthy
adults, including 106 young and 111 older participants, as well as a replication cohort
of 117 young subjects. We further tested the stability and generalizability of both
scores by controlling for different MR scanners and gender, as well as by using different data sets of young adults as reference samples. Both scores showed robust agegroup-related differences for the subsequent memory contrast, and the FADE-SAME
score additionally exhibited age-group-related differences for the novelty contrast.
Furthermore, both scores correlate with behavioral measures of cognitive aging,
namely memory performance. Taken together, our results suggest that single-value
scores of memory-related fMRI responses may constitute promising biomarkers for
quantifying neurocognitive aging