BOLD fMRI activations and LC contrast associated with successful episodic memory in healthy older adults and MCI.

INTRODUCTION

We examined whether locus coeruleus (LC) contrast, an indirect proxy for neuronal density and structural health, was related to delayed episodic memory in healthy older adults (OAs) and those with mild cognitive impairment (MCI) and its association with encoding-related brain activity, controlling for emotional salience.

METHODS

Participants (27 younger adults, 26 OAs, and 24 MCI) memorized emotional and neutral images during functional magnetic resonance imaging (MRI). Delayed memory was tested after 4 h and compared to immediate memory. LC contrast was measured via LC-sensitive MRI.

RESULTS

Memory was lower, independent of delay or emotional valence, and LC contrast was more strongly reduced in those with MCI compared to OAs. In OAs, LC contrast correlated with delayed memory and was mildly associated with LC activity during successful encoding. All groups remembered emotional images better than neutral ones, though memory was greatly impaired in those with MCI.

DISCUSSION: LC contrast was associated with lower brain activity during encoding and emotional salience processing. Its relationship to delayed memory was evident in those with MCI.