Poster Session A, Saturday, March 23, 1:30 pm - 3:30 pm, Pacific Concourse
Age-related modulation of functional connectivity along the long-axis of the hippocampus
Shauna Stark1, Amy Frithsen1, Craig Stark1; 1University of California, Irvine
A number of lines of evidence, from neuroanatomical through functional imaging, have supported the notion that the hippocampus demonstrates circuit-level specificity of function, both when segmented based on subfields (CA1, CA3, DG, and subiculum) and along the longitudinal axis. There is also evidence that aging may have differential effects affects across subfields (e.g., DG/CA3) and along the longitudinal axis. For example, there is evidence for an age-related shift in functional connectivity in the hippocampus from anterior to posterior regions (Blum et al., 2014; Damoiseaux et al., 2016). However, the ratio of hippocampal subfields varies along the longitudinal axis of the hippocampus and may better capture these age-related alterations in connectivity. Here, we sought to evaluate the functional connectivity profile between the hippocampus and the medial temporal lobe to determine how these segmentation models capture age-related changes in this circuit. We calculated subfield-level volume and functional connectivity during an incidental recognition memory task in 31 young (20-39 years) and 31 older (70-87 years) adults, controlling for differences in regional volume. We replicated the age-related functional connectivity shift (e.g., hippocampus to parahippocampal cortex) from the anterior to the posterior hippocampus. The degree of this shift also predicted mnemonic discrimination performance in older adults. Critically, the DG/CA3 is most represented in the anterior portions, suggesting that the anterior to posterior shift can be accounted for, in part, by subfield-specific computations as they are disproportionally represented along the long axis of the hippocampus.
Topic Area: LONG-TERM MEMORY: Development & aging