I just learned an interesting theory about the physical mechanics behind what artists call being "in the zone". It seems that our brains' neurons can only process data at a rate of about 120 bits per second. By way of comparison it takes 60 bits per second to just listen to someone speaking. Which means that it is hard to understand for us to listen with comprehension to more than two people talking at the same time. So when we perform a complex action visualizing a subject while simultaneously rendering on a canvas there isn't enough "bandwidth" for us to notice our physical sensations or our surroundings. Hence the feeling of being outside ourselves when we are fully absorbed in the painting process. Same thing applies to any other fully engrossing activity like playing jazz or doing yoga. Cool Heh?
Click on the following link for Wikipedia 's more detailed, but understandable explanation, of what Mihaly Cjkszentmihalyi called his Flow Theory : http://en.wikipedia.org/wiki/Mihaly_Csikszentmihalyi