Scientists have long known that when we enter the phase of sleep in which dreams occur, our eyes dart about rapidly. But what exactly are eyes doing when we experience rapid eye movement (REM) sleep?
A new study suggests that our eyes are essentially visualizing new images that we "see" in our dreams. In fact, our eyes seem to respond to those images in much the same way they would respond to seeing something while awake.
"Our goal was to examine what happens inside the brain when we dream, specifically at moments when rapid eye movements occur," Dr. Yuval Nir, a neuroscientist at Tel Aviv University in Israel and co-author of the study, said in a written statement. "We discovered that the electrical brain activity during REM sleep is very similar to what occurs when the viewer sees new images for the first time."
For the study, the brain activity of 19 epilepsy patients whose brains had been fitted with electrodes was monitored for two weeks -- both while the patients were awake and while they were asleep.
The researchers observed that neurons in the medial temporal lobe -- a brain region associated with visual perception and memory -- showed a surge of activity around a quarter of a second after patients moved their eyes during REM sleep, New Scientist reported. The researchers concluded that after the rapid eye movements occur the dreaming brain produces new images.
"Even people who are congenitally blind... can still dream about their aunt coming to visit from Florida: her voice, the emotions and all the associations that go with that," Nir told BBC News. "And when the dream changes from meeting this aunt to, say, taking your dog for a stroll in the park, then the brain activity changes and this happens in sync with eye movements."
The scientists hope that, with additional research, they might be able to link brain activity in dreaming patients to specific dream imagery.
The study was published online in the journal Nature Communications on August 11, 2015.
Why do we dream? Check out the "Talk Nerdy To Me" video below to learn more about the elusive world of dreaming.