When Kundalini awakens in the spine, the vibration/sensation of “mirth” is—to me—an unusual frequency of Her “resonance.” What I mean by this is that when Kundalini builds up to a certain threshold in the spine, the body may shake, contort, move in unusual ways…and the mind, as observer/witness of this strange “dance,” is able to watch itself merge with the strong current of what I think of as “mirth.”
To me, mirth is a connecting with a bubbly, high frequency, child-like energy that brings out an aspect of the personality that is like a “crackpot,” or “Divine Fool.” Movements of the body can become very fast, moving automatically, rhythmically with the delicious sensations felt within.
In the context of Kundalini, for me the experience of mirth (and its ensuing exuberance) happens only during certain conditions, usually right before going to bed. I believe the textures of sheets, blankets and the luxurious sensations of “melting” into pillows and blankets has a way of activating the mirth response in the spine.
I also think it interesting that this “activation” right before sleep does not usually impede the process of falling asleep. Rather, it has become a wonderful way to enter the realms of sleep!