In a study published in the journal Nature Communications, researchers offer first scientific evidence linking rapid eye movement (REM), accelerated brain activity and dream images.
REM is the period of sleep in which people experience vivid dreams. It was discovered in the 1950s and has been associated with dreaming and eye movement but scientists have not been able to prove that eye movement coincides with a particular dream image. According to the study, however, eye movement during REM sleep occurs alongside sudden activity surges in the brain resembling patterns observed when a new image is seen while awake.
Dr. Yuval Nir from the Sackler Faculty of Medicine at the Tel Aviv University explained that the goal of the study was to explore what happens deep within a person's brain during REM sleep, particularly when rapid eye movement occurs. Thanks to research on epilepsy patients carried out by Prof. Itzhak Fried, also from TAU, the study was able to acquire the data it needs about neuron activity in the human brain.
For the study, the researchers worked with 19 patients with epilepsy, all of which needed invasive brain activity monitoring before potential surgical removal of areas of their brain causing their seizures. Electrode implants were used to monitor the subjects' brain activity for 10 days.
Nir and colleagues focused on electrical activities recorded for individual neurons located in the medial temporal lobe, the part of the brain that bridges memories and visual recognition. Based on research done by Fried, neurons in the region are shown to turn active almost immediately after people view pictures of famous places and people, even when eyes are closed and concepts are simply imagined.
Additionally, the researchers also gathered other information about the subjects, including data on scalp EEGs, eye movements and muscle tone, which was used for identifying REM sleep periods and detecting the exact moment that each rapid eye movement occurred.
According to the results of the study, electrical brain activity when rapid eye movements are observed has similarities to what is registered when a person sees a new image. Nir added that the burst of activity is also present in neurons in the hippocampus.
"How and why eye movements occur are important," said Nir, adding that every moment a movement occurs is an opportunity for researchers like him to study brain activity.
Other authors of the study include Thomas Andrillon, Chiara Cirelli and Giulio Tononi.
Photo: Pedro Ribeiro Simoes | Flickr
