Circuit mechanism for suppression of frontal cortical ignition during NREM sleep. (https://pubmed.ncbi.nlm.nih.gov/38070510/)

These scientists wanted to understand why our brain works differently when we are asleep compared to when we are awake. They focused on a specific process called conscious perception, which is how we become aware of things around us. They studied mice because they have similar brain structures to humans.

They used a special type of imaging called functional ultrasound imaging to see how the mouse brains were working. They also used a technique called calcium imaging to look at specific types of cells in the brain. To control the activity of these cells, they used a method called optogenetics, which involves using light to turn them on or off.

The scientists found that a process called cortical ignition, which is important for conscious awareness, was strongly suppressed during a specific stage of sleep called non-rapid-eye-movement (NREM) sleep. They discovered that this suppression happened because of reduced activity in a part of the brain called the basal forebrain, which normally helps to activate the cortex.

They also found that during NREM sleep, the activity between different parts of the brain, specifically from the visual cortex to the frontal cortex, was greatly reduced. This was because the frontal pyramidal neurons, which are important for communication between these areas, were strongly inhibited.

The scientists then focused on a specific type of brain cell called parvalbumin-expressing interneurons. They found that these cells were more active during sleep compared to when the mice were awake. They also discovered that these cells were important for controlling the activity of the frontal pyramidal neurons.

By manipulating the activity of these parvalbumin interneurons, the scientists were able to show that they strongly influenced the process of cortical ignition during sleep and wakefulness. This means that these cells play a big role in how our brain switches between being awake and asleep.

Overall, this study helped the scientists understand how our brain works differently during sleep, particularly in terms of conscious perception. They discovered that certain brain cells and their activity patterns are important for this process, and they hope that this knowledge can help us understand sleep better and potentially find ways to improve our sleep in the future.

Li B., Ma C., Huang YA., Ding X., Silverman D., Chen C., Darmohray D., Lu L., Liu S., Montaldo G., Urban A., Dan Y. Circuit mechanism for suppression of frontal cortical ignition during NREM sleep. Cell. 2023 Dec 21;186(26):5739-5750.e17. doi: 10.1016/j.cell.2023.11.012. Epub 2023 Dec 8.