Part of the Mouse Brain is Made "Sleeping" While the Body Remains Awake

JAKARTA - Researchers have managed to trigger a sleep-like recovery process in certain parts of the brain of mice that are still awake. In a memory test, the stimulus helped reduce the impact of sleep deprivation.

The National Institutes of Health or NIH quoted from its official website on Tuesday, July 21, saying the research team triggered a special pattern of activity in a small part of the mouse's brain. This pattern mimics the activity that usually appears during non-rapid eye movement or NREM sleep.

"Basically, we force one part of the brain to sleep," said Chiara Cirelli, a professor of psychiatry at the University of Wisconsin-Madison who was a corresponding author of the study.

According to Cirelli, the stimulated part of the brain can strengthen memories and restore learning abilities. At the same time, other parts of the brain remain conscious, alert, and connected to the environment.

He compared the process to dolphins being able to sleep using one hemisphere of the brain at a time.

NREM sleep is a phase of sleep without rapid eye movement and accounts for about 80 percent of an adult's sleep time. During this phase, the brain reassesses the connections between nerve cells that form memories.

Important relationships are retained for long-term storage. Relationships that are less needed are reduced to make room for new information.

Previous research has shown that sleep-deprived mice and humans can experience slow wave activity in small parts of the brain even while awake. Slow waves are a pattern of brain activity that is an important feature of NREM sleep.

However, its appearance is too short and irregular so that it is likely not enough to provide benefits. Researchers then tried to trigger a similar pattern for longer and more directed.

They used a small implant that emits light as well as genetic modifications in the mouse nerve cells. Stimulation was given on one side of the brain for 30 minutes with alternating patterns between active and inactive.

When the mice then slept, the slow wave activity in the part of the brain that had been stimulated was lower. This indicates that the part no longer needs as much recovery during sleep as before.

Further experiments found that the benefit did not just come from decreased neural cell activity. The recovery effect depends on the pattern of alternating activity regularly.

The researchers then tested tactile memory, which is the ability to recognize and remember stimuli through touch. This ability is strongly influenced by sleep.

Sleep-deprived mice who received stimulation to the part of the brain that regulates movement and processes tactile stimuli showed results almost identical to mice who got enough rest.

In contrast, sleep-deprived mice without stimulation showed much worse results.

The findings are still from animal studies and cannot be applied directly to humans. This method also does not mean that sleep can be replaced with brain stimulation.

Cirelli plans to investigate the possibility of producing a similar effect in humans through transcranial stimulation. The technology provides stimulation from outside the head and is not as intense as the method used on mice.

"This research further explains why we sleep and how we learn," said Amy Bany Adams, acting director of the National Institute of Neurological Disorders and Stroke or NINDS, an agency under the NIH that funded the research.

According to Adams, the findings can help further research on the prevention and treatment of cognitive decline.