Real-time talk with a sleeping person is possible -- and they can even understand it

A study participant sleeps in the lab as electrical signals from his brain and eyes are displayed on a computer monitor.

(CNN)People can say all sorts of strange things in their sleep, but a new study suggests that someone in the middle of a vivid dream can understand questions -- and even answer them.

Dreams have been widely studied, and experts are still trying to understand why we have them, how dream scenarios are created, and whether dreaming benefits brain function.
But remembered dreams are often full of forgotten details and distortions, so experts from Northwestern University wanted to speak to people as they dreamt in real time, to learn more about why dreams happen, and how they might be useful for mental function.
    Scientists attempted to speak to people during lucid dreams. While lucid dreaming, people report that they are aware that they are dreaming, and often say they are able to direct or manipulate the dream's content to some degree.
    In separate experiments in the US, France, Germany and the Netherlands, scientists studied 36 people with varied experiences of lucid dreaming, establishing two-way communication between subjects and asking questions using sensory stimulation, including touching, beeping noises and flashing lights.
    "We presented questions to individuals in the midst of lucid dreams, and they were able to answer with eye movements or muscle contractions," Karen Konkoly, cognitive neuroscientist at Northwestern and one of the paper's authors, told CNN over email.
    A study participant in a full EEG rig just before a sleep session in the lab. The electrodes on his face will detect the movement of his eyes as he sleeps.
    Researchers found the dreamers could follow instructions to do simple mathematical equations, answer "yes-no" questions, and differentiate between visual tact