What Happens to the Brain During Sleep? Answering this question is a bit like trying to find out if the light in the fridge stays on when you close the door … A mystery, then. Except for researchers of Inserm, ESPCI Paris, CNRS and Sorbonne. To better understand what happens when we sleep, they filmed the brain of a sleeping rat using an ultrasound imaging technique, reports the Nature Communications journal.
In particular, researchers have explored REM sleep. The study explains that this moment of sleep is characterized both by cerebral activity close to that of awakening, and by totally inhibited muscle activity. At this stage of sleep, the eyes are very active. While it is often associated with the dream phase, recent studies have pointed out that it was also the moment of sleep that allowed neurons to reconfigure their connections, notes the Inserm site.
Filming the brain during REM sleep
Two related technologies have been used in the brains of mice. On the one hand, the technique of electroencephalography to analyze the electrical activity of neurons, and imaging via extremely fast ultrasound. This innovative technique of biomedical ultrasound makes it possible to visualize the blood flows linked to neuronal activity.
Thanks to this device, the researchers realized that REM sleep is a phase of cerebral hyper-synchronization, in which the body makes significant peaks in blood flow, particularly in the hippocampus. Apart from these phases of sleep, the brains of mice have rather low blood volumes.
In addition, the video of the brain made it possible to see that distant cerebral areas (cortex, hippocampus and thalamus) were experiencing an unprecedented vascular synchronization phenomenon in the paradoxical sleep phase. This discovery advances research on understanding the coupling between electrical and vascular activity. To the extent that this phenomenon occurs in diseases such as epilepsy or stroke, it could help to better understand the mechanism of these dysfunctions, although the technique is not yet usable on humans.
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