Is there an energy center located at the base of the skull? I thought I had read somewhere that there was a chakra there. How important is this energy center?

I've noticed at times when I'm in deep thought and arrive at an enlightening revelation, that this area will feel like it's expanding. It's a massive rush of energy isolated to this area.

The chakra, if thats what it truely is, is not like the major chakras that one can "turn on". This one seems to be noticable only when I'm in deep thought about spiritual matters. More importantly, the intensity of the energy becomes greater when I approach an answer I feel is correct, and fades when I feel I'm drawing the wrong conclusion.

I'd be grateful for any information you can share about this energy center.
Thanks!