1. Age effects on hippocampal functional connectivity during multifeatural encoding Chris Foster 1, Milton Picklesimer 1, Neil Mulligan, Ph.D. 1, and Kelly Giovanello, Ph.D. 1,2 1 University of North Carolina at Chapel Hill, Department of Psychology; 2 Biomedical Research Imaging Center Background Several recent studies have suggested that aging leads to a alteration in the ability for older adults (OAs) to utilize task positive networks (TPN) and to simultaneously deactivate the default mode network (DMN) during working memory and episodic memory as compared to young adults (YAs) 1. The hippocampus is critical for encoding and retrieval of episodic memories and is thought to decouple with the DMN during encoding but couple with the DMN during retrieval 2. Importantly, prior research investigating functional connectivity differences between OAs and YAs have not equated performance, leaving open the question of whether changes occur due to effort or qualitative differences in the types of memory. The current study investigated task related functional connectivity changes between a group of OAs and YAs during multifeatural encoding. The left hippocampus was used as a seed to test whether DMN decoupling would be altered by age. Methods Discussion Results Behavioral Results References Cited 1 Sambataro et al., (2010). Age-related alterations in default mode network: Impact on working memory performance. Neurobiology of Aging, 31, 839-852. 2 Huijbers et al., (2011). The hippocampus is coupled with the default mode network during memory retrieval but not during memory encoding. PLoS One, 6(4), 1-9. 3 Rissman, et al., (2004). Measuring functional connectivity during distinct stages of a cognitive task. Neuroimage, 23, 752 - 763. Participants Eleven OAs (mean age = 73.94 years; 60 - 86) and eleven YAs (mean age = 21.29 years; 19 - 23) participated in this study. According to the hippocampal decoupling hypothesis, the hippocampus should be recruited as a part of a task positive network during encoding. Results suggest that YAs are able to successfully deactivate the DMN during encoding and that the hippocampus is part of a localized network during multifeatural encoding. Despite matched behavioral performance OAs recruit a diffuse encoding network that contains many regions associated with both TPN and DMN. The hippocampal network associated with encoding during this task suggests OAs exhibit the well established dedifferentiation of activity as well as an inability to decouple the hippocampus from the DMN. Procedure No main effects and no interaction. Functional Connectivity Results ICL>all: For successful multifeatural encoding both groups recruited a hippocampal correlated network including the bilateral middle temporal, superior temporal, and occipital lobe. No significant main effect of age or age x hit-type interaction. Main effect of hit type where IC had the lowest proportion hits. 5.5 sec Animacy Decision + Study 500 ms ITI fixation Example Study Trial 6 sec Old/New Decision 8 sec Color Decision 8 sec Location Decision Example Test Trial OA > YA: OAs recruited a hippocampal correlated network that included several DMN regions (Posterior Cingulate, Inferior Parietal, and Precuneus) as well as TPN regions (occipital, lateral frontal, and temporal). YA > OA: YAs recruited a localized TPN that correlated with hippocampal activity including the Occipital lobe, Bilateral middle frontal, Left superior temporal gyrus, and Caudate. Analysis A beta series correlation analysis was used to analyze trial-by-trial functional connectivity between the left hippocampus (-30, -15, -19 MNI coordinates; 6mm sphere) and all other voxels in the brain 3. DMN Connectivity Results Using the posterior parietal cortex as a seed, both groups show the typical DMN including posterior cingulate, angular gyrus, and parietal cortex ; however, YAs recruit more medial frontal regions including bilateral frontal pole and superior frontal gyrus while OAs recruit middle and inferior frontal, paracingulate, and bilateral anterior parietal regions Using a mask created from each groups DMN, only OAs exhibited overlap between activity during multifeatural encoding and their DMN. This occurred in the left superior temporal gyrus, bilateral posterior cingulate, left angular gyrus, and right precuneus.