By implanting electrodes to stimulate the brain in a specific area of the cortex, doctors have been able to trigger complex and vivid hallucinations of past memories.
From New Scientist:
A 22-year-old man has been instantaneously transported to his family’s pizzeria and his local railway station – by having his brain zapped. These fleeting visual hallucinations have helped researchers pinpoint places where the brain stores visual location information.
Pierre Mégevand at the Feinstein Institute for Medical Research in Manhasset, New York, and his colleagues wanted to discover just where in the brain we store and retrieve information about locations and places. They sought the help of a 22-year-old man being treated for epilepsy, because the treatment involved implanting electrodes into his brain that would record his neural activity.
Mégevand and his colleagues scanned the volunteer’s brain using functional MRI while he looked at pictures of different objects and scenes. They then recorded activity from the implanted electrodes as he looked at a similar set of pictures.
In both situations, a specific area of the cortex around the hippocampus responded to images of places, but not to images of other kinds of objects, such as body parts or tools. “There are these little spots of tissues that seem to care about houses and places more than any other class of object,” says research team member Ashesh Mehta, also at the Feinstein Institute.