Scientists identify neural switch for dreaming
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. Yang Dan, a professor of molecular and cell biology at UC-Berkeley, and 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.
The team recently published their findings in the journal Nature.
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.
GABAergic neurons protrude from the ventral part of the medulla, situated at the top of the spinal cord and certain regions of the brainstem and the hypothalamus - a brain region involved in hormone release and many other bodily functions.
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.
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