Scientists have uncovered a new method of activating dream state during sleep.

Scientists have uncovered a new method of activating dream state during sleep. (Source: Library of Congress Prints and Photographs Division)

Sleep is regarded as a necessary but uncontrollable aspect of daily life. That description may change, however, owing to the work of a team of neuroscientists at the University of California, Berkeley.

The team developed a method to activate rapid eye movement (REM) in sleeping mice. REM sleep and non-REM sleep are the two fundamental components of the sleep cycle (1). In addition to being associated with rapid eye movements, REM sleep is characterized by complete muscular paralysis, activation of the brain’s cortex, and dream formation (2).

Due to the cortical activation that occurs, the brain during REM sleep more closely resembles the awake brain than the brain in non-REM sleep (2). It is logical, then, that humans dream in this state, as dreams appear as depictions of life when awake.

This research on REM sleep may help scientists better understand when and why humans dream (2). However, understanding REM sleep has implications far beyond the scope of the sleep cycle: REM sleep patterns tend to be altered by drug use, mood disorders, and diseases such as Alzheimer’s disease and Parkinson’s disease (2).

The researchers at the University of California, Berkeley began to tackle these issues by identifying what controls REM sleep in mice. As it turns out, the secret lay with a group of neurons in the medulla, a region of the brain stem (2). These neurons – deemed GABAergic due to their release of gamma-amino butyric acid (GABA) – were also found to stimulate eating and grooming while the mice were awake, suggesting their role in controlling pleasurable actions (2).

Additionally, these neurons had been previously shown to invoke the muscular paralysis associated with REM sleep. However, this team demonstrated that the neurons are in fact responsible for the immediate triggering of all aspects of REM sleep (2). In fact, Yang Dan – one of the neuroscientists on the team – claimed that “94 percent” of the mice “entered REM sleep within seconds of activating the neurons” (2).

These results mimic the process of flicking a light switch on or off, which is actually not far from the technique used for this experiment. The technique used is called optogenetics and offers a way to control neurons using light. The researchers first used a virus to tag the GABAergic neurons with a light-sensitive ion channel (2). This was possible because the mice in the experiment were genetically engineered to display a specific protein only on those exact neurons (2). Finally, the scientists shined a laser light into the brain via an optical fiber, and this light triggered the ion channels to open and allow GABA to flow through, activating the neurons and resulting in REM sleep (2).


  1. Robinson, J. (2014, October 22). What are REM and non-REM sleep? Retrieved October 18, 2015, from
  1. University of California – Berkeley. (2015, October 15). Dreams turned off and on with a neural switch: Activating small group of neurons in medulla causes rapid transition to REM sleep. ScienceDaily. Retrieved October 18, 2015 from