Déjà vu is the phenomenon that a person experiences when they feel that they’ve experienced an event in their past. Studies show it’s not a psychic experience, but rather a little trick the brain does. Déjà rêvé, however, is something different and there’s no trick to it.

A new study in the journal Brain Stimulation explained a phenomenon epileptic patients experienced where they were able to recall a dream or have a dream-like feeling while awake called déjà rêvé. Déjà vu is French for “already seen” while déjà rêvé means “already dreamed.”

For the study, researchers searched through reports from 1958 to 2015 of epileptic patients who experienced the phenomena after being induced with electrical brain stimulation (EBS).

Although this sounds like something out of A Nightmare On Elm Street, the researchers view this study as a way to separate the feeling of déjà vu from déjà rêvé and learn more about our dreams.

“EBS-induced déjà rêvé could be an interesting approach to better understanding physiological dreams that cannot be reproduced under laboratory conditions,” says lead author Jonathan Curot, a Ph.D. student at Toulouse University Hospital. “Most studies focus on REM (rapid-eye movements) sleep period and dream reports obtained by awakening a sleeping subject. However, non-REM sleep dreams account for a significant portion of all typical dreams and several factors might render dream reports less trustworthy — especially the sleep stage before awakening — when compared with reports of waking experience.”

Three Kinds of Déjà Rêvé

The study states déjà rêvé happens in three different ways. In one, referred to as “episodic-like,” a patient is spontaneously able to specify that they had a certain dream on a definite date.

“‘I saw something, a dream, a nightmare I had a couple years ago. A dream of an object lying on a table,” said one subject about their event.

The second is refereed to as “familiarity-like,” or when a patient reminisces of a vague dream. One subject explained that they had a vision of a scene from a recent dream.

Lastly, researchers found many patients in their literature experienced a “dreamy-state.” They would have a feeling of being in a dream, or nightmare. A subject tried to explain it as feeling like they passed out and floating.

Déjà rêvé is still a new phenomenon, but this study is the first step to explaining those strange, unexplained dreamy feelings that people have.