Deja Vu refers to those odd and usually rare moments when the present feels like the past. Its a hard experience to interpret. Some people search their memories for dreams that might have been like the present.

Others think that the experience is what happens when things from past lives emerge in this one. Both notions are impossible to prove, disprove, or (until recently), investigate.

The belief that its about past lives is a matter of faith. The idea that it has to do with dreams is less a matter of faith - only a few people claim to recall past lives, but almost everybody remembers some of their dreams.

Some recall a lot of them. The theory of reincarnation that is most consistent with modern brain science (Algorithmic Reincarnation) predicts that no memories are passed from one life to the next. What is transferred is a set of signals that reflect states of consciousness.

Memories don't need to go along

*Memories are state-specific. We can have experiences in one state of consciousness (like when we are drunk, for example) that we cannot remember at all when we are in another.

States of consciousness provide a much more direct way for someone to select how they will behave than remembering past behaviors and comparing them to present possibilities.

*There is a fly in the ointment with dreams as well. Both dreams and deja vu experiences happen in non-normal states of consciousness. Most altered states are a fertile ground for confabulations.

This means that in the moment when someone is experiencing deja vu, its easier for them to create a false memory than it would be normally.

In fact, during moments of deja vu , one's consciousness has unusually direct access to long-term memories, and the brain processes that allow us to retrieve them.

*I'm not going to write it here that deja vu doesn't come from past lives or dreams, and that that's just how it is.

But we want to understand what deja vu is, and how we can respond to it when it happens.

If we explain it in terms of past lives and dreams, we are giving ourselves explanations that can't be proven.

Or proved to be false.

It will boil down to a matter of faith.

*There are some people who experience precognitive dreams, but most episodes of deja vu happen without the person having any sense of it relating to a dream.

Precognitive dreams are a different matter altogether.

Having the present moment feel like a repeat of something from the past is not the same as having the present validate a previous precognition.

 I have spoken to some professional psychics about this, and one of them said that he could tell the two apart, but that it took him some time to learn the difference.

I asked him what the difference was, and he said that it was an 'energy.'

That's not really enough to help understand what the difference was, but enough for us to know that there might be one.

How does deja vu happen?

The scientific explanation is that it has to do with memory processes.

I'll make it as simple as I can here. The basic idea is that there are portions of the brain that are specialized for the past, the present and the future.

In general, the frontal lobes are concerned with the future, the temporal lobes are concerned with the past, and the underlying, intermediate portions (the limbic system) are concerned with the present.

When these are all doing their normal thing, in normal states of consciousness, the feeling that something is going to happen will only come up when we are thinking about the future, worrying about it, anticipating it or making plans for it.

The sense of the past will only come up when our memories have been triggered in some way.

*The structure that overwhelms our consciousness when we are 'in the present are 'being here now' is the amygdala. It assigns an emotional 'tone' to our perceptions.

When you step into the street and see a car speeding towards you, and you instantly freeze in terror and jump out of the way, that terror is the amygdala at work.