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As if losing their memories weren't bad enough, some amnesia patients can't imagine the future, either.
Scientists have known that damage to the brain's hippocampus, known to play a crucial role in learning and memory, can lead to amnesia. The hippocampus can be damaged when oxygen supply to the brain is temporarily cut off or by certain illnesses such as Alzheimer's disease. (Amnesia can also be caused by sudden head trauma, of course.)
In a new study of people with a damaged hippocampus, researchers asked the patients to describe plausible future events, such as a Christmas party or a future meeting with a friend.
"We found that the role played by the hippocampus in processing memory was far broader than merely reliving past experiences," said Eleanor Maguire of the University College London. "It also seems to support the ability to imagine any kind of experience including possible future events. In that sense, people with damage to the hippocampus are forced to live in the present."
Patients also reporting being unable to visualize an entire experience in their mind's eye, seeing instead a collection of separate images, Maguire said.
The hippocampus might provide the spatial context or environmental setting into which the details of our experiences are bound, Maguire and colleagues write this week in the Proceedings of the National Academy of Sciences.