Different Types of Deja VuOnline Learning
While most people use the term déjà vu—already seen—to describe a moment that suddenly seems familiar, the more appropriate term might be déjà vecu—already lived through. Déjà vecu is the perception that you already know many details about a particular time and place; occasionally people feel that they can predict what happens next.
The phenomenon of uncanny familiarity can be broken down even further:
• Déjà visité (already visited) —when you are in a new place or landscape and suddenly feel like you’ve been there before
• Déjà senti (already felt)—feeling that you’ve had the same thought or feeling, under the same circumstances, in some previous point in time
• Jamais vu (never seen) —when you don’t recognize something as familiar, though it must be
• Presque vu (almost seen)—when a thought or realization seems imminent, but ends up being elusive
• L’esprit de l’escalier (stairway wit)—when your clever reply to someone suffers a maddening time lag
All of these strange experiences might be categorized as “cognitive feelings.” Cognitive feelings might function to keep the different aspects of memory organized. When there’s a glitch, it shows how fallible memory can be.
Persistent Déjà Vecu
Persistent or repetitive déjà vu sounds like a joke—but people who live with this syndrome can find it extremely debilitating. Usually affecting older people, the sense of déjà vecu—already having lived through the present moment—can make reading a newspaper or watching TV unbearable since people feel like they have already read the same news or watched the same program before. Brain imaging has revealed abnormal temporal lobe damage in these cases, suggesting that this is where a “recollective experience circuit” is located. With déjà vecu, the sense of recollection is no longer tied to a specific memory.
Memory and Pattern Recognition
Scientists at the Picower Institute for Learning and Memory at MIT have proposed that there are two aspects of memory: pattern separation, which distinguishes between similar but different memories, and pattern completion, which allows us to access a whole memory when one aspect of it is triggered. Mice that were missing the gene for pattern separation, for instance, had a harder time differentiating between a room where they had received a mild electric shock and a room without any shock. Déjà vu may result when someone’s pattern separation circuit misfires so that they are unable to keep similar memories properly sorted. The eerie feeling arises because the brain recognizes that something unusual just happened in our neural network—a brain fart, if you like.
While neurobiologists might find déjà vu and other memory system malfunctions useful for what they might tell us about how normal memory is organized, for many of us those surprising moments when we are jolted by a hiccup in the usual linear sequence of time might be eerie—but they are also mysterious and marvelous.