But in a certain sense, a set of blank scans could be far more interesting. What would it mean if someone had an intense emotional experience that didn't show up on a brain image? What if you loved vanilla ice cream, but your cortex was indifferent to it? Even Andrew Newberg admits that "the most interesting result from a brain scan of someone in prayer would be to find no significant change in the brain," especially at the moment of the most profound spiritual experience.
Believers might take a negative result in the glossolalia study as proof of divine intervention. I'd be more inclined to wonder about the design of the experiment or suspect the subjects had lied about their experiences. Either way, the scanner won't give the final answer. It merely tells us what's already inside our heads.