Scientists from the University of California-Berkeley have sent a sleeping mouse to the land of dreams with the flip of a switch.
Falling from a mountain? Being chased but can’t scream? We can all recall such vivid bad dreams that caused us to wake up in the middle of the night. Sweating, with a lingering fear that made us spend the rest of the night without sleep. What if there was a switch that we could use to turn off such a dream? The possibility looks closer than ever before, after scientists from the University of California – Berkley said that they have uncovered a neural switch that would turn off or on dreams.
The research team led by Yang Dan, a professor of molecular biology at UC-Berkeleydiscovered that activating certain neurons in medulla – an area of the brain, prompted Rapid Eye Movement (REM) sleep in mice in a matter of seconds. When they deactivated the neurons, it impaired their ability to enter REM sleep.
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In mammals, REM is a stage of sleep that makes up about 25 percent of sleep cycle, with the first phase usually occurring about 70-90 minutes after falling sleep. With characteristics of fast, random eye movements and temporary muscle paralysis, REM is involved in the process of dreaming. Researchers based their study on the hypothesis that the lack of muscle control that occurs during REM sleep should stop us from dreaming.
Some facts about dreaming:
·
We lose 90% of our dreams within 1 minute of
waking up
·
6 years of our lives spent on dreaming
·
Babies start to dream of themselves only after
they reach the age of 3 years.
According to the findings published in the journal Nature, the researchers aimed to get a better perception of whether GABAergic neurons in the medulla – which are active during REM sleep, play a role in generating REM sleep.
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GABAergic neurons stick out from the ventral part of the medulla. This part is at the top of the spinal cord and certain regions of the brainstem and the hypothalamus, a region involved in releasing hormone and other bodily functions.
The mice involved in the research 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, allowing them to activate or deactivate the neurons by using laser light.
After insertion, the researchers activated the GABAergic neurons in mice by kindling them with a laser light through an optical fiber placed in the brain. To deactivate the GABAergic neurons with laser light, they inserted an inhibitory ion pump into the neurons.
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They tracked the GABAergic neurons’ activity during activation and deactivation and also assessed how switching them on or off affected the sleep and wake behavior of the mice.
The researchers found that the activation of GABAergic neurons in the medulla of sleeping mice prompted REM sleep within seconds, while deactivation of these neurons either diminished or even eliminated a mouse's ability to enter REM sleep.
“Because of the strong induction of REM sleep -- in 94 percent of the recorded trials our mice entered REM sleep within seconds of activating the neurons -- we think this might be a critical node of a relatively small network that makes the decision whether you go into dream sleep or not,” said lead author Yang Dan.
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The authors believe that this discovery will not only help them better understand the complex process of sleep and dreaming, but will allow scientists to stop and startdreaming at will in mice to learn why we dream.
Shed light on psychiatric and neurological disorders
The researchers noticed that GABAergic
neurons in awaken mice didn’t impact their wakefulness, but affected their
appetite, causing them to eat more. GABAergic neurons in normal mice are
highest during waking periods and eating and grooming time, which are the two
enjoyable activities for mice.
According to professor Yang, GABAergic
neurons in the opposite effect to nerve cells involved in stress, such as
noradrenergic neurons in a part of the brain called the pons.
“Other people have found that
noradrenergic neurons, which are active when you are running, shut down when
eating or grooming,” says prof. Yang. “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.”
Researchers say that their findings not
only helped them better understand brain mechanisms behind sleep and dreaming,
they are now also able to switch dreaming on and off in mice at will, which
could have clinical implications.
Franz Weber, first author and a
postdoctoral fellow at UC-Berkeley said: “Many psychiatric disorders,
especially mood disorders, are correlated with changes in REM sleep, and some
widely used drugs affect REM sleep, so it seems to be a sensitive indicator of
mental and emotional health.”
Weber believes, studying the sleep
course will not only offer insight into psychiatric disorders, it could also
help scientists understand neurological disorders that impact sleep, such
Parkinson’s disease and Alzheimer’s disease.
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