Memories are stored in pieces all over the brain

Recalling a happy memory seems like popping a favorite movie in the VCR, but Harvard's Dan Schacter shows Alan Alda that human memories are much less dependable than videotape.

In "True or False," Schacter has Alan watch a staged scene in which a couple enjoys a picnic. When Alan leaves, a photographer take pictures of the scene, including some things Alan never witnessed.

Recalling true events lights up the auditory cortex

Three days later, Schacter shows Alan the photos, asking him to identify which things really happened and which he'd seen only in the photographs. Alan mistakenly "recalls" a few scenes he never witnessed, proving that memory is malleable.

That's not surprising, given that memory is stored in bits and pieces all over the brain, with the hippocampus acting as an index. Armed with that knowledge, Schacter PET scans a brain as it is remembering, and actually sees the difference between real and false memories.