From a UPI story of the same title on belief.net:

U.S. scientists, in a first-of-its-kind study, have found decreased brain activity in people "speaking in tongues," a condition known as glossolalia.

The unusual mental state is associated with some religious traditions and occurs when people appear to be speaking in an incomprehensible language, yet perceive it to have great personal meaning.

"Our brain imaging research shows us that these subjects are not in control of the usual language centers during this activity, which is consistent with their description of a lack of intentional control while speaking in tongues."