There was a fascinating demonstration on the last _Scientific American
Frontiers_ (like the magazine, the show is more concerned with liberal
politics and entertainment than scientific integrity, but an occasional
gem slips though the fog). They read lists of words to the subjects,
then had then read back the list from memory while being PET scanned.
Each word list had a theme, and each one left out some words obviously
belonging to that theme, so naturally some people "remembered" those
words. The PET scans, though, were clearly distinguishable--especially
by activity in the auditory region--between those words actually heard
and those "remembered" falsely. Something like this is bound to show
up in a courtroom before long.