A) Older participants have a significantly higher ratio value than young adults, indicating greater DG/CA3 activity relative to alEC. Conversely, young participants have a near-zero mean ratio, indicating relatively balanced engagement of both regions. B) Object discrimination performance negatively correlates with this normed ratio in older adults, indicating greater DG/CA3 activity relative to alEC is associated with poorer object mnemonic discrimination. Despite a qualitatively similar relationship in young participants, the relationship does not yield a significant correlation. (Solid regression lines indicate significant whole-sample correlations, whereas broken regression lines indicate significance for a given age group).