Researchers at the University of Liège used 7 Tesla magnetic resonance imaging (MRI) to discover the role of ganglia in regulating sleep, especially REM sleep. They found that activity in this cerebellar nucleus is related to the quality of REM sleep, with its function diminished to initiate and allow REM sleep, a pattern that was particularly pronounced in people aged 50 to 70 years.
A study carried out by a research team at the Institute of the University of Liège (Belgium) using ultra-high magnetic field 7 Tesla MRI technology has deepened the understanding of the mechanisms of sleep regulation. We've long known that sleep is good for the brain. We also know that light is not only useful for seeing, but also plays an important role in mood and other aspects.
What we don't know is how this happens in our brains. Researchers at the University of Liège conducted two separate studies using a 7-Tesla MRI machine on the GIGA-Centre de Recherche du Cyclotron (Cyclotron Research Center) platform, which provides us with the premise for an explanation.
A scientific team from the Liège Cyclotron Research Center/In Vivo Imaging (GIGA-CRC-IVI) has just demonstrated that the quality of REM sleep (the stage of sleep in which we dream most) is related to the activity of the ventricular lobules. This cerebellar nucleus, which is about the size of a 2-centimeter-long noodle, is located at the base of the brain (brainstem).
In Latin, it means "spot coeruleus," so named because of the color it appears when dissected. It projects to nearly all areas of the brain (as well as the spinal cord), secreting a neuromodulator called norepinephrine. Norepinephrine is important not only for stimulating neurons and keeping them awake, but also for a range of cognitive processes such as memory, emotional processing, stress and anxiety. Its stimulating activity must subside to initiate sleep and cease before rapid eye movement sleep can occur.
Gilles Vandewalle, co-director of GIGACRC-IVI, explains: "This way, REM sleep can work without norepinephrine, sorting out the synapses that need to be preserved or eliminated during sleep, thus facing a new day full of new experiences."
Animal studies have shown that the function of this small nucleolus is critical for sleep and wakefulness. Ekaterina Koshmanova, a researcher in the laboratory and the first author of the article published in "JCI Insight", explained: "In the human body, due to the small size and deep location of nerve nuclei, it is difficult to observe them in vivo with traditional magnetic resonance imaging. Therefore, There are few confirmed results. Thanks to the higher resolution of 7 Tesla MRI, we were able to isolate this nucleus and extract its activity while performing a simple cognitive task in the waking state, showing that the more strongly our outer cerebellar lobe responds during the day, the worse our sleep quality and the lower the intensity of REM sleep."
This appears to be particularly true with age, as the effect was only found in the study among people aged 50 to 70, but not among younger adults aged 18 to 30. This finding could explain why some people develop progressive insomnia as they age. These preliminary results also pave the way for future research into the activity of this small nucleus during sleep and its possible role in insomnia and the link between sleep and Alzheimer's disease.
Meanwhile, the same research team is also trying to better understand how light stimulates our cognition. Light is like a cup of coffee, helping us stay awake. Therefore, we recommend not using too much light on smartphones and tablets at night. This can disrupt our sleep. On the other hand, the same light helps us during the day.
Many studies have shown that good lighting can help school students, hospital staff and patients, and corporate employees. The most effective at this is the blue part of the light, since we have blue light detectors in our eyes that tell our brains about the quality and quantity of light around us.
Likewise, the brain regions responsible for this stimulating effect of light (also known as the "non-visual" effects of light) are not well understood.
In 7T magnetic resonance imaging, parietal (A) and thalamic (B) regions were involved in more complex auditory cognitive tasks while participants were illuminated. The image on the right is a time course reconstruction of activity during a 25-minute recording period. (C) Location of different nuclei in the thalamus and the thalamic regions used for analysis. It is this latter area that receives light information and changes activity in parietal areas. Image source: University of Liège/GIGACRCIVI
"They are small and located under the cerebral cortex," explains Ilenia Paparella, an FNRS doctoral student in the lab and first author of the article published in Communications Biology. The research team from GIGA-CRC-IVI once again used the high resolution of 7 Tesla MRI technology to demonstrate that the thalamus, a subcortical region located beneath the corpus callosum (connecting the two hemispheres of the brain), plays a role in transmitting non-visual light information to the parietal cortex, the area that controls attention levels.
"We know its important role in vision, but its role in non-visual aspects is less certain. This study demonstrates that the thalamus stimulates parietal regions, and not the other way around as we thought. These new advances in understanding the role of the thalamus will ultimately allow us to come up with lighting solutions that aid cognition when we need to be fully awake and focused, or promote better sleep with relaxing light."