Memories can't be recovered from long dead brain matter, the brain after a few minutes would begin to break down, including the neurons, making memories unrecoverable. So, a brain after it's been dead for hours would not be able to give out any memories like is shown in the movie when one is "eaten".
When Julie and R are running away from the Bonies, they run through the parking garage to use the red convertible to get away. As Julie is getting into the car, she grabs the windshield to sling herself in the driver's seat. Since the windshield is dusty, you can see where she grabbed the windshield from past takes of filming.