ISLAMABAD: What if dreams could be turned on or off with the flick of a switch? This possibility may be not be too far off, after researchers from the University of California-Berkeley say they may have uncovered a way to do just that.
Researchers found that activating GABAergic neurons in the medulla of the brain immediately induced REM sleep - the dream phase - in mice.
Yang Dan with other colleagues found that activating certain neurons in a brain region called the medulla induced rapid eye movement (REM) sleep in mice in a matter of seconds, while deactivating the neurons impaired their ability to enter REM sleep.
REM is a stage of mammalian sleep that makes up around 25% of our sleep cycle, with the first phase normally occurring around 70-90 minutes after falling asleep.
As well as being characterized by fast, random eye movements and temporary muscle paralysis, REM is involved in the dreaming process. Researchers hypothesize that the lack of muscle control that occurs during REM sleep is to stop us from acting out our dreams.
For their study, Dan and colleagues set out to gain a better understanding of whether GABAergic neurons in the medulla - which are active during REM sleep - play a role in REM sleep generation.
The team used a technique called optogenetics on mice that were genetically engineered to express a marker protein in GABAergic neurons only. The optogenetics method involved placing a light-sensitive ion channel into the GABAergic neurons using a virus. Once inserted, the researchers activated the GABAergic neurons in mice by stimulating them with a laser light via an optical fiber placed in the brain. The team was able to deactivate the GABAergic neurons with laser light by inserting an inhibitory ion pump into the neurons.
The researchers tracked the activity of GABAergic neurons in the medulla of the mice during both activation and deactivation with optogenetics. They also assessed how switching these neurons on or off for short periods affected the sleep and wake behavior of the mice.
The team found that activating the GABAergic neurons in the medulla of sleeping mice induced REM sleep within seconds, while deactivating these neurons during sleep either reduced their ability to enter REM or stopped that sleep phase completely.
Findings could shed light on psychiatric, neurological disorders.
While activating the GABAergic neurons in mice that were awake did not impact their wakefulness, it did affect their appetite, causing them to eat more. The researchers note that in normal mice, activity of GABAergic neurons is highest during waking periods and during eating and grooming - which the team notes are two enjoyable activities for mice.
"Other people have found that noradrenergic neurons, which are active when you are running, shut down when eating or grooming," says Dan. "So it seems like when you are relaxed and enjoying yourself, the noradrenergic neurons switch off and these GABAergic neurons in the medulla turn on."