Vannini P, Hedden T, Sullivan C, Ward A, Becker JA, Johnson KA, Sperling RA.
Age and amyloid deposition are associated with functional alterations in posteromedial cortex during encoding and retrieval processes.
Human Amyloid Imaging 2011 Meeting Abstracts. 2011 Jan 15;
Cortical s-amyloid deposition is a major histopathological finding in Alzheimer's disease and a likely contributor
to the observed memory impairment. The posteromedial cortices are particularly vulnerable to early amyloid
pathology and are thought to play a key role in both memory encoding and retrieval processes. The extent to
which aging and amyloid influence modulation of fMRI activity during encoding vs retrieval remains an open
question. In this study, we used in vivo amyloid imaging to investigate the impact of fibrillar amyloid burden on
fMRI activity during encoding and retrieval in clinically normal older individuals.
Twenty-six young (M = 23.3) and 41 elderly (M = 70.9) subjects underwent fMRI scanning while performing a facename
associative encoding and retrieval task. Elderly subjects were imaged with 11-C PiB-PET and each individualfs
mean cortical PiB retention ratio was calculated. A conjunction analysis of deactivation during encoding and
activation during retrieval revealed anatomical overlap in bilateral posteromedial cortices (p = 0.001). In this region,
a negative correlation (r = -0.43, p = 0.02) was observed between the modulation of functional response (ƒ¢ change of
the functional response elicited during retrieval minus encoding) and age, suggesting that older individuals have a
restricted dynamic range in the modulation between deactivation and activation in these regions. Among the older
subjects, amyloid deposition was inversely correlated with modulation of functional response (r = -0.55, p Our study supports the hypothesis that the posteromedial cortices represent a critical node in episodic memory
function and exhibit a dynamic response to encoding and retrieval processes. As these regions are vulnerable to
early amyloid deposition, our findings may serve to elucidate the neural underpinnings of memory dysfunction
seen in aging and neurodegenerative disease.