Human brain activity during rapid eye movement (REM) sleep is remarkably similar to activity observed during waking vision reports a paper published this week in Nature Communications. This research may explain why subjects waking from REM sleep often report vivid dream imagery.

During REM sleep our eyes move around much like they do when we are awake and looking at a visual scene. Scientists have long wondered whether REMs reflect the processing of visual information during sleep.

Yuval Nir and colleagues recorded brain activity from 19 people. They found that individual neurons in the medial temporal lobe (an area important for long-term memory formation) of the brain responded similarly when patients made REMs during sleep, wakefulness, as well as during visual stimulation scene. This suggests that REMs during sleep correspond to periods of visual-like processing and may indeed reflect visual imagery during dreams.