A team of UC Berkeley and Stanford University neuroscience researchers can move a sleeping mouse into a dream state and back again, simply by pointing a laser at its brain.
The researchers inserted genetically modified viruses into certain portions of the mice’s brains to make them more sensitive to light. The mice were then primed for scientists to activate and deactivate those portions responsible for REM sleep, the highly active sleep state in which vivid dreams occur.
Their work could have significant implications, not just for understanding the complex and still unclear processes behind REM and non-REM sleep, but for medical applications, according to Franz Weber, a postdoctoral researcher and one of the authors of the study, published earlier this month.
“Many psychiatric disorders are visible in REM sleep … (It) is a very sensitive marker of mental and emotional health,” said Weber, who went on to explain that if we can better understand the precise links between brain activity and psychiatric disorders, scientists may one day have a “new venue to treat psychiatric health.”
In the paper reporting their findings, the team — which includes UC Berkeley professor of neurobiology Yang Dan and three campus postdocs — discussed how the brains of mice function during sleep.
The work has focused on understanding which regions of the brain are active during REM sleep compared with non-REM sleep, according to Weber.
“The function of sleep is not very fully understood,” said Min Xu, another UC Berkeley postdoc and a co-author of the paper, discussing why the group has been conducting this research. “This will help us to understand internal mechanisms of being asleep and awake,” he added.
Through their experiments with rodents, the researchers were able to determine that the brain’s ventral medulla is highly active during REM sleep. They then altered the rodents’ brains so that neurons — which show an increase in activity during REM sleep — would respond more readily to laser light.
The group’s recent paper is the product of several years of research. According to Weber, who joined Dan’s lab three and a half years ago, the lab began studying sleep a year after he arrived.
In November 2013, Weber determined which portion of the brain was most directly linked to REM sleep. Following this breakthrough, the team successfully induced REM sleep in mice for the first time.
The team has since been able to move mice in and out of REM sleep, among other actions — such as inhibiting certain neurons in the ventral medulla and experimenting with different structures within the brain.
Members of the team are currently examining how to move mice in and out of sleep through the direction of brain activity, according to Shinjae Chung, a UC Berkeley postdoc and co-author.