Getting enough sound sleep is very crucial in maintaining the health of both the mind and body. It helps the brain in recuperating and refreshing itself; it also gives it the break to process memories. Sleep is also important to keep the body's immune system sound.
A paper published in the Proceedings of the National Academy of Sciences, it was revealed that researchers at MIT were successful in producing natural sleep patterns in mice using optogenetics. For this technique light was shone directly on mouse neurons and it triggered a period of rapid eye movement (REM)
Emery Brown, the Edward Hood Taplin Professor of Medical Engineering at MIT and the leader of the research team said that the different stages of sleep offer different benefits. There have been studies in rodents which reveal that learning occurs in the REM sleep, while the non-REM sleep is the one that makes one feel rested and refreshed. He further added that in a sound natural sleep there is an alternating 90 minutes period of non-REM and REM sleep. Currently, no drug is known that can induce that state of sleep. The present methods to induce sleep only create sedation and if one is lucky sedation allows the natural sleep mechanisms to take over.
Brown said that the goal of their research is to create natural sleep. For that researchers need to experiment to find the extent to which the various sleep stages can be created first separately and finally together.
Christa Van Dort, a postdoc in Brown’s group in the Department of Brain and Cognitive Sciences at MIT and the study's lead author said that there have been previous studies which indicated that neurons called cholinergic cells are active during both wakefulness and REM sleep. But, it was not known whether the firing of these neurons was responsible for the transition to REM sleep. In order to ascertain if cholinergic neurons had the ability to induce REM sleep, the team made use of a technique called optogenetics. In this technique a head-mounted fiber optic device is used to shine light onto a specific group of neurons.
The neurons are first sensitized to light using a protein found in algae. The protein when inserted into certain types of neurons activates when shine a light is shone on them. By shining the light one can control the firing of the brain, at a single-cell level. Van Dort and her colleagues used the technique on a mouse known to express this algae protein in cholinergic neurons and they were able to trigger dream sleep in the mice. It was also discovered that activation of cholinergic neurons during non-REM sleep increased the number of REM sleep episodes the mice experienced. On further analysis it was found the REM sleep episodes matched natural periods of REM sleep.
Van Dort said that the technique is a step toward understanding how to design natural sleep in humans. Brown added that by knowing how to trigger more episodes of REM sleep could also be used to enhance people’s learning and memory.
The researchers now aim to investigate how the cholinergic system connects with other areas of the brain that have also been identified as important in REM sleep production. They are also in the process of developing experiments with the aim to produce better non-REM sleep.
Van Dort said that the long-term goal of their study is to really understand what controls each phase of non-REM and REM sleep, and how to selectively induce both of them. With the help of this study they hope to reproduce the normal cycling of sleep stages.