Why Our Eyes Dart About When We Sleep

When awake, our eyes are taking in a lot of visual information that necessitate these to dart in every possible direction.  When asleep, though, our eyes do not process any visual data.  Or do they?  Have you ever wondered then why our eyes seem to flick here and there under our eyelids during sleep, as if seeing something?  If dream images could be considered visual info, then this may possibly explain the phenomena of REM or rapid eye movement.

What is REM?

REM sleep or rapid eye movement sleep is a sleep phase in mammals that is characterized by brisk, erratic eye movements, relaxed and paralyzed muscles, and intense neurological activity...  We undergo five stages of sleep of which REM is a short phase cycling about 4-5 times a night.  Dreaming is believed to transpire during the REM phase.  Dreams at the REM phase are supposed to be at their most vivid.

Do Our Darting Eyes Actually See Anything During Sleep?

Ever since the concept of REM sleep came to the fore in the 50’s, scientists have been wondering whether our eyes are actually seeing images from our brain.  Some people have acted out their dreams by reaching for an object, for instance, when seeing it in a dream.  Most of the time, however, people don’t physically move when dreaming; so, it is difficult to accurately say that eye movements match the dream visuals.  Besides, babies still in the womb and people who have been blind since birth exhibit the same rapid eye movements.  How can their eyes be following, say an object, if these particular persons have never experienced vision nor have really known how to keep an object in sight?

A recent study conducted by Tel Aviv University researchers confirms that brain signals during the dreaming state are very similar to those when we are awake and seeing an image or even imagining something new.  Whenever a sleeping person’s eyes flickered or moved, the researchers recorded bursts of neuron activity.

The study published in Nature Communications  offers proof of the links between rapid eye movement, dream images, and accelerated neuronal activity.  The Tel Aviv researchers took the advantage of monitoring the brain activity during sleep of 19 epileptic participants who needed brain implants of electrodes for monitoring prior to their surgery.

The research focused on the medial temporal lobe which serves as a bridge between visual recognition and memories.  According to Yuval Nir, the lead author of the study, prior research have confirmed that when people are shown popular images such as the Sydney Opera House or Hugh Jackman, the neurons in the medial temporal lobe become highly active about 0.3 seconds after the image is seen.  When we close our eyes and imagine images, these neurons also become activated.

Now the research showed similar neuronal activity during REM.  The brain acts the same way it does when our eyes see an actual image or when we just see the image in our imagination (or in dreams, too.)  Nir says that the neurons burst into activity right after eye movements in sleep as much as they do when the eyes are presented with new actual images.

During the REM phase, the darting eye movements do not really mean that the eye is scanning a dream scene.  The movements are believed to be responses to scene changes or the introduction of new images in the dream.  Each flick of the eyes signal an incoming new dream visual.  This may explain why blind people undergo REM too.  Instead of visuals, they may receive sounds and emotions in dreams.  When these stimuli take on some variations, the eyes will dart about the same way normal eyes do when seeing something new.

Satoru Miyauchi, manager of the Advanced ICT Research Institute in Japan, supported the above study with his own with the fMRI (Functional Magnetic Resonance Imaging).  A test subject is made to sleep inside the machine which records images of his brain during the REM stage.  The results of Miyauchi’s research shows particular activity in the primary visual cortex of the brain during REM sleep.  This area of the brain receives the visual information from our eyes when we are awake.  This has led Miyauchi to conclude that “at least part of this vigorous eye movement is related to watching images in our dreams.”