Neuroscientists from University of California, Berkeley have been able to control when a sleeping mouse enters a dream state by simply flipping a switch. They achieved this by inserting an optogenetic switch into the medulla and activating the neurons with a laser light. Activating the neurons would send the sleeping mouse into REM sleep in under a minute. When the neurons are inactivated, it completely hindered the mouse’s ability to go into REM sleep altogether.
Yang Dan, UC Berkeley professor of molecular and cell biology, says, "People used to think that this region of the medulla was only involved in the paralysis of skeletal muscles during REM sleep. What we showed is that these neurons triggered all aspects of REM sleep, including muscle paralysis and the typical cortical activation that makes the brain look more awake than in non-REM sleep."
This study used a technique called optogenetics, which involves the insertion of light-sensitive ion channels into specific neurons using a virus. The virus was made to target specific neurons by genetically engineering a mouse line that expresses a marker protein. This new discovery will help researchers better understand the nature of dreaming and sleep.