Investigators at Penn used SPECT imaging to look at women subjects speaking in tongues. Quite a fascinating result (click on the link to the NY Times report).
Money quote:
[The] frontal lobes — the thinking, willful part of the brain through which people control what they do — were relatively quiet, as were the language centers. The regions involved in maintaining self-consciousness were active. The women were not in blind trances, and it was unclear which region was driving the behavior.
Interestingly the caudate nucleii had relatively lower activity.
Jim
Discoverers and Discoveries 