Oh H, Mormino E, Jagust W.
Effects of Age and Beta-Amyloid Deposition on Brain Activity and Functional Connectivity during Episodic Memory Encoding in Cognitively Normal Elderly.
Human Amyloid Imaging Abstract. 2012 Jan 1;
Objectives: To examine how brain activity and effective connectivity underlying episodic encoding change as a function of age and amyloid deposition measured by [11C] Pittsburgh compound B (PIB) positron emission tomography (PET).
Method: Eleven young (“YOUNG”, mean age=22.8, 7 males), 18 PIB-negative (“PIB−OLD”, mean age=76.8, 7 males) and 11 PIB-positive (“PIB+OLD”, mean age=77.5, 4 males) older adults performed an episodic encoding task of visual scenes during fMRI scans, followed by a surprise recognition task outside of the scanner where subjects made an old/new judgment. 200 encoding trials were sorted based on recognition judgment as correct recognition with high (“HC”) or low (“LC”) confidence or incorrect (“INCORRECT”) recognition (i.e., misses).
Results: Whole-brain analyses revealed that, for the HC versus INCORRECT, YOUNG showed increased activity in frontal, parietal and visual association areas compared to both PIB−OLD and PIB+OLD. PIB−OLD showed increased activity in hippocampus and medial frontal cortex compared to YOUNG. Psychophysiological interaction (PPI) analyses was performed to evaluate connectivity with a seed region in the right parahippocampal gyrus (rPHG), which is implicated in visual processing and which was defined by a HC-INCORRECT contrast in each subject (mean coordinates X = 27, Y = -26, Z = -18). This revealed stronger coupling between rPHG and the left posterior hippocampus in YOUNG than PIB−OLD while, for the same contrast, PIB−OLD showed stronger coupling than YOUNG between the rPHG seed and the left frontal and parietal cortices, middle temporal cortex and the lateral occipital cortices. Within the older subjects, PIB−OLD showed stronger coupling between the rPHG and frontal and parietal cortices than PIB+OLD.
Conclusion: These preliminary results indicate that activity in prefrontal cortices, hippocampus, and visual association areas undergoes age-related alterations in support of successful visual encoding and that connectivity across these regions are further affected by age and amyloid deposition.