Summary: Researchers have shed light on the vital role of the locus coeruleus in regulating REM sleep and its effects on cognitive processes. Located deep in the brain, this nucleus manages noradrenaline, influencing memory, emotions, and sleep initiation.
Using advanced 7 Tesla MRI, the studies revealed a correlation between locus coeruleus activity during the day and REM sleep quality. Intriguingly, this connection seems more prominent in individuals aged 50-70, potentially explaining age-linked insomnia.
The locus coeruleus, dubbed the “blue spot”, regulates REM sleep through its management of noradrenaline.
A reactive locus coeruleus during wakefulness correlates with reduced REM sleep quality, especially in those aged between 50 and 70.
The findings could pave the way for understanding the role of this nucleus in sleep disorders and its connection with Alzheimer’s disease.
Source: University of Liege
We’ve known for a long time that sleep is good for the brain. We also know that light is not just for seeing, but also plays an important role in other aspects such as mood. What we don’t know is how all this happens in our brains.
Two separate studies, carried out by researchers at the University of Liège using the 7 Tesla MRI on the GIGA-Centre de Recherche du Cyclotron platform, offer the premises of an explanation.
A scientific team from the ULiège Cyclotron Research Centre /In Vivo Imaging (GIGA-CRC-IVI) has just demonstrated that the quality of our REM sleep (the part of sleep during which we dream the most) is linked to the activity of the locus coeruleus. This small brain nucleus, the size of a 2cm-long spaghetti, is located at the base of the brain (in the brainstem).
The locus coeruleus – Latin for “blue spot” – owes its name to its color when observed in autopsy. It projects to just about every area of the brain (and to the spinal cord) to secrete a neuromodulator called noradrenaline.
Noradrenaline is not only important for stimulating neurons and keeping them awake, but also for a whole series of cognitive processes such as memory, emotional processing, stress and anxiety. Its stimulating activity must diminish to initiate sleep and stop to allow REM sleep.
“This allows REM sleep to work without noradrenaline, sorting out the synapses that need to be retained or eliminated during sleep and enabling a new day, full of new experiences,” explains Gilles Vandewalle, co-director of the GIGA CRC-IVI.
Animal research has already shown that the functioning of this small nucleus is essential for sleep and wakefulness.
“In humans, little has been verified because the small size of the nucleus and its deep position make it difficult to observe it in vivo with conventional MRI,” explains Ekaterina Koshmanova, a researcher in the laboratory and first author of the article published in JCI Insight.
“Thanks to the higher resolution of 7 Tesla MRI, we were able to isolate the nucleus and extract its activity during a simple cognitive task during wakefulness, and thus show that the more reactive our locus coeruleus is during the day, the poorer the perceived quality of our sleep and the less intense our REM sleep”.
This seems to be particularly true with advancing age, as this effect was only detected in the individuals aged between 50 and 70 included in the study and not in young adults aged between 18 and 30. This finding could explain why some people become progressively insomniac with age.
These initial results also lay the foundations for future studies on the activity of this small nucleus during sleep and the role it could play in insomnia and in the link between sleep and Alzheimer’s disease.
About this neuroscience, sleep, and memory research news
Locus Coeruleus activity while awake is associated with REM sleep in older individuals
BACKGROUND. The locus coeruleus (LC) is the primary source of norepinephrine in the brain and regulates arousal and sleep. Animal research shows that it plays important roles in the transition between sleep and wakefulness, and between slow wave sleep and rapid eye movement sleep (REMS). It is unclear, however, whether the activity of the LC predicts sleep variability in humans.
METHODS. We used 7 Tesla functional Magnetic Resonance Imaging, sleep electroencephalography (EEG) and a sleep questionnaire to test whether the LC activity during wakefulness was associated with sleep quality in 33 healthy younger (~22y; 28 women) and 19 older (~61y; 14 women) individuals.
RESULTS. We found that, in older, but not in younger participants, higher LC activity, as probed during an auditory attentional task, was associated with worse subjective sleep quality and with lower power over the EEG theta band during REMS. The results remained robust even when accounting for the age-related changes in the integrity of the LC.
CONCLUSION. These findings suggest that LC activity correlates with the perception of the sleep quality and an essential oscillatory mode of REMS, and that the LC may be an important target in the treatment of sleep and age-related diseases.
FUNDING. This work was supported by Fonds National de la Recherche Scientifique (FRS-FNRS, T.0242.19 & J. 0222.20). Action de Recherche Concertée – Fédération Wallonie-Bruxelles (ARC SLEEPDEM 17/27-09), Fondation Recherche Alzheimer (SAO-FRA 2019/0025), University of Liège, European Regional Development Fund (Radiomed & Biomed-Hub).