Hidden Nook

There were clear differences between the liars and the truth-tellers, Faro's team told a meeting in Chicago of the Radiological Society of North America.

"We found a total of seven areas of activation in the deception
(group)," he said. "We found four areas of activity in the truth-telling arm."

Overall, it seemed to take more brain effort to tell the lie than to tell the truth, Faro found.

Lying caused activity in the frontal part of the brain --- the medial inferior and pre-central areas, as well as the hippocampus and middle temporal regions and the limbic areas. Some of these are involved in emotional responses, Faro said.

During a truthful response, the fMRI showed activation of parts of the brain's frontal lobe, temporal lobe and cingulate gyrus.

Faro said the study was small and limited. Volunteers were not asked to try especially hard to deceive the equipment, he said -- noting that it has been documented that some people can fool a polygraph using various techniques.

Using fMRI as a lie detector is expensive, but it may be worthwhile in some cases -- such as trying to question a terrorism suspect, or in a high-profile corporate crime case, Faro said.