Associations between Locus Coeruleus integrity, sleep physiology, and attention in humans using 7T MRI

Given its extensive noradrenergic ramifications, the locus coeruleus (LC) is implicated in several processes, including sleep-wake regulation and cognition. Whether variability in LC integrity is related to sleep quality and cognitive performance in humans is not established. Here, we assessed whether age-related changes in LC structural integrity, assessed with 7 Tesla Magnetic Resonance Imaging (MRI), is related to sleep electroencephalography (EEG) and selective attention.
72 healthy participants (45 young, 22.5±3y; 27 late middle-aged, 61±6y) underwent structural 7T MRI to image the LC and compute the LC-contrast, related to its integrity. A night of sleep was monitored in-lab, from which we extracted Rapid Eye Movement (REM) theta energy, sigma-power preceding REM, and sleep spindles density. Besides, participants completed the D2 test for selective attention, from which we extracted processing speed ₋ errors (Gz₋F) and concentration performance (KL). Statistical analyses consisted of Linear and Generalized Linear Models.
Regarding sleep physiology, sigma-power preceding REM was positively associated with LC-contrast (p=0.039). Spindle density showed a significant positive main-effect of LC-contrast (p=0.026), LC-contrast*Age (p=0.034) and LC-contrast*Age2 (p=0.039) interactions. No significant associations were observed with REM theta energy (ps>0.47). Regarding cognition, the integrity of the LC was not associated with the attention-related metrics (p=0.88 and p=0.92, respectively for Gz-F and KL), and no significant LC-contrast*Age or LC-contrast*Age2 were detected.
These results suggest that the integrity of the LC is related to sleep physiology depending on age, but not to selective attention. In future analyses, we will assess potential triadic relationships between LC, sleep, and cognition.