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Study Finds Twitches during Sleep Activate the Brain in a Unique Way

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Have you wondered about the twitches baby do while asleep and their possible connection with development of brain? That might seem like an unlikely hypothesis, but a recent study at the University of Iowa which appeared this month in the journal Current Biology is pointing towards the same. The research reveals that twitches during the rapid eye movement (REM) sleep activates the brain in a unique way and it is different from the movement made while awake. There is significant evidence that sleep twitches teaches new born babies about their bodies.

The researchers say that the twitches during REM sleep consists of a different class of movement and it activates circuits throughout the developing brain and thus it educates newborns about their limbs and what they can do with them. Alexandre Tiriac, a fifth-year graduate student in psychology at the UI and first author of the study said that every time we move while we are awake, we understand that it is we who made the movement because there is a mechanism happening in the brain which lets us understand the same. But, twitches do not work the same way because our brain is unaware that it is self-generated.


The study says that these self-generated twitches which are more frequent in early infancy have something to do with the brain development. Mark Blumberg, a psychology professor at the UI and senior author of the study remarked that this discovery is further evidence that sleep twitches, be it in dogs, cats or human are not connected to dreams but to brain development.

In order to carry out this study, Blumberg, Tiriac and fellow graduate student Carlos Del Rio-Bermudez studied the brain activity of unanesthetized rats which were around 8 and 10 days of age. The brain activity of these animals while awake and when they were moving was measured. Their brain activity while they were in REM sleep and twitching was also measured.

The results of these observations were somewhat puzzling. It was noticed that there was a lot of brain activity when the rats were sleeping but not when they were awake and moving. The researchers hypothesized that sensations as a result of the twitching limbs during REM sleep were being processed differently in the brain than the movements made by them while awake. That is because the movements lacked what is known as “corollary discharge.”

Corollary discharge was first introduced by researchers in 1950. It is actually a split-second message sent to the brain that allows animals like rats, crickets, humans and more, to recognize and filter out sensations generated from their own actions. This filtering of sensations is what that lets animals to distinguish between sensations that arise from their own movements and those that are a result of stimuli from the outside world.

The researchers carried out several follow-up experiments to determine whether sleep twitching is a unique self-generated movement that is processed as if it lacks corollary discharge. The experiments supported the idea consistently that the sensations arising from twitches are not filtered. And since, the filtering is not provided by the corollary discharge, the sensations which results due to twitching limbs activate the brain and teach the newborn brain about the structure and function of the limbs. If the twitches during sleep were same as the wake movements, the signals should have been filtered out. Since, they are not filtered; they suggest that they are different. The researchers at the University of Iowa were also surprised to find the filtering system functioning so early in development.