[Mark Lapierre]

For a neurological opinion read Descartes' Error by Antonio Damasio. He suggests that there is a constant, poorly defined background feeling "against which we can be aware of myriad other things which manifestly change around [us]." It's a feeling which, in neurological terms, is not mapped to any specific location in the body, but is rather an internal representation of overall body state.

I suspect this feeling is the feeling which we experience when we reach that point of no-thought. The perceptual images which we normally think of as thought are quietened and all that is left is the perception of that persistent awareness of the state of our body. We're not usually aware of it because of the distraction our thoughts and perceptions cause.