Recognition memory is associated with hippocampal volume in aging population: new evidence from brain imaging study

Introduction. The hippocampus is crucial for episodic memory, especially for recollection and
pattern separation (i.e., the ability to store similar episodes as distinct memory traces).
Episodic memory declines with aging and this has been associated with hippocampal
dysfunction. The main objective of our study was to explore how performance on a
recognition memory task designed to assess pattern separation is associated with hippocampal
volume in aging population. Methods. Fourteen healthy late middle-aged participants (52-69
years-old) were evaluated on a Mnemonic Similarity Task (MST). In this task, participants
study pictures and then have to discriminate between targets, similar lures, and unrelated foil
objects. Recognition memory (RM) is assessed as the difference between hits and false alarms
to unrelated foils, while pattern separation Bias metric (BPS) is the difference between the
rate of ‘‘Similar’’ responses given to the lure items minus ‘‘Similar’’ responses given to the
foils. Hippocampal volume was calculated using ASHS software, which uses T1-weighted
and T2-weighted MRI to obtain optimal segmentation of hippocampal subfields. Results.
Correlation analysis of preliminary data revealed that RM was significantly positively
associated with the volume of the left subiculum and left perirhinal area 35, while there were
no significant correlations in the right hemisphere. BPS was positively correlated with the
volume of right CA2 region, but negatively associated with the volume of right CA3 region,
what is more contradictory according to the current literature. No significant link was found
between BPS and the volume of hippocampal subfields in the left hemisphere. Conclusion. In
a middle-aged population, better visual recognition memory is associated with larger volume
of the left subiculum and perirhinal area 35, two regions supporting representation of objects