What does deja vu

Sometimes, as we experience a new event or place, we get that creepy feeling that it's not the first time.

That explanation is perfect for cyberpunk science fiction, but it doesn't give us any scientific understanding of the phenomenon. But scientists have tried using tricks like hypnosis and virtual reality. In a study by Leeds Memory Group, researchers would first create a memory for patients under hypnosis. That memory was usually something simple like playing a game or looking at a printed word in a certain color.

For example, all of the bushes in a virtual garden were replaced with piles of trash to create a junkyard with the same layout. So our brain recognizes the similarities between our current experience and one in the past. Beyond this general explanation, there are dozens of theories that attempt to explain why our memories might malfunction in this way. Others blame the rhinal cortex—the area of the brain that signals that something feels familiar—for somehow being triggered without the memories to back it up.

However, researchers have begun to push back on this idea. The first time you see something, you might take it in out of the corner of your eye or while distracted. Your brain can begin forming a memory of what you see even with the limited amount of information you get from a brief, incomplete glance. So, you might actually take in more than you realize. In other words, it can happen as a sort of mix-up when the part of your brain that tracks present events and the part of your brain that recalls memories are both active.

When your brain absorbs information, it generally follows a specific path from short-term memory storage to long-term memory storage. The theory suggests that, sometimes, short-term memories can take a shortcut to long-term memory storage.

Another theory offers the explanation of delayed processing. You observe something, but the information you take in through your senses is transmitted to your brain along two separate routes.

One of these routes gets the information to your brain a little more rapidly than the other. This delay may be extremely insignificant, as measurable time goes, but it still leads your brain to read this single event as two different experiences.

This process of implicit memory leads to the somewhat odd feeling of familiarity. You may have experienced this yourself. The reddish wood of the desk, the scenic calendar on the wall, the plant in the corner, the light spilling in from the window — it all feels incredibly familiar to you. Cleary also explored this theory. They can last for a minute or two, but they could end after only a few seconds.

You might also experience other symptoms, such as:. Experts generally agree this phenomenon probably relates to memory in some way. Crystal Raypole has previously worked as a writer and editor for GoodTherapy. These signals can move through cells in the brain like dominoes, each one knocking over the ones that it is next to.

In people with temporal lobe epilepsy, we know that seizures start in the temporal lobe. This is a part of the brain just inside from the top of your ears, and it is important for making and remembering memories look at Figure 2 to see where the temporal lobe is.

The familiarity is signaled by brain cells in the temporal lobe, but is noticed and ignored by another part of the brain that checks whether all the signals coming to it make sense. The part of the brain that does this checking may well be in the frontal lobe, a part of the brain in from just above your eyes. We know the frontal lobe is important for making decisions.

The experience is important because it shows us that remembering happens with a series of steps, some of which can go wrong.

Our thanks go to Cassie Teale, who created all the artwork used in Figure 1.