Activation studies using functional brain mapping are almost all subtractive, in that they report on the difference in brain activity between two tasks. For the most part, we can't say anything about performing one task; we have to compare two.
At the Human Brain Mapping meeting in San Francisco, there is a presentation today on the difference, in the brains of deeply religious people, between praying to God and talking to Santa Claus. The point of this, according to the authors, is that these people know that God is "real" while Santa Claus is "fictitious". (Although a friend of mine insists that just the opposite is true.)
Thought for the day: If yesterday's presentation on functional brain mapping in a dead fish resembles Monty Python's "Dead Parrot" sketch, perhaps today's presentation on God vs. Santa resembles the infamous 1995 South Park "Spirit of Christmas" pilot, in which Jesus does battle with Santa over the meaning of Christmas.