New research reveals that neurons in the preoptic hypothalamus—the region of the brain that regulates sleep and body temperature—are rhythmically activated during non-rapid eye movement sleep (NREM). Stress activates these brain cells out of turn, causing “microarousals,” that interrupt sleep cycles and decrease the duration of sleep episodes, according to research from Perelman School of Medicine, published in Current Biology.
While our bodies are at rest when we are asleep, our brains are still very active during four different stages of sleep. In each 90-minute sleep cycle, there are three stages of NREM sleep, and one stage of rapid eye movement (REM) sleep. During the first two stages of NREM sleep, brain waves, heartbeat, and breathing slow, and body temperature decreases. Stage two also includes unique brain activity, called spindles and K-complexes, which are short bursts of activity responsible for processing outside stimuli, as well as for consolidating memory. Stage three of the NREM sleep cycle is when the body releases growth hormone, which is important for repairing the body, keeping the immune system healthy, and further improving memory. During phase three, brain waves are larger, called delta waves. REM sleep, which happens in this phase when dreaming normally occurs, is also critical for memory formation, emotional processing, and brain development.
“When you have a bad night of sleep, you notice that your memory isn’t as good as it normally is, or your emotions are all over the place—but a bad night of sleep interrupts so many other processes throughout your body. This is even more heightened in individuals with stress-related sleep disorders,” says senior author Shinjae Chung, an assistant professor of neuroscience. “It’s crucial to understand the biology driving the brain activity in these crucial stages of sleep, and how stimuli like stress can disrupt it, so that we might someday develop therapies to help individuals have more restful sleep that allows their brain to complete these important processes.”
Read more at Penn Medicine News.
