Memory and Database

Sunday, November 12, 2006

Artificial Human Memory

The world's first brain prosthesis - an artificial hippocampus.

This silicon chip implant will perform the same processes as the damaged part of the brain it is replacing.

Way to help people who have suffered brain damage due to stroke, epilepsy or Alzheimer's disease.

What does the Hippocampus do?
It "encodes" experiences so they can be stored as long-term memories elsewhere in the brain.

"If you lose your hippocampus you only lose the ability to store new memories," says Berger (Theodore Berger of the University of Southern California in Los Angeles.) That offers a relatively simple and safe way to test the device: if someone with the prosthesis regains the ability to store new memories, then it's safe to assume it works.

The inventors of the prosthesis had to overcome three major hurdles:
1). Devise a mathematical model of how the hippocampus performs under all possible conditions.
2). Build that model into a silicon chip.
3). Interface the chip with the brain.

It is not understood how the hippocampus encodes information. So the team simply copied its behavior. Slices of rat hippocampus were stimulated with electrical signals, millions of times over, until they could be sure which electrical input produces a corresponding output. Putting the information from various slices together gave the team a mathematical model of the entire hippocampus.

They then programmed the model onto a chip, which in a human patient would sit on the skull rather than inside the brain. It communicates with the brain through two arrays of electrodes, placed on either side of the damaged area. One records the electrical activity coming in from the rest of the brain, while the other sends appropriate electrical instructions back out to the brain.

The hippocampus can be thought of as a series of similar neural circuits that work in parallel, says Berger, so it should be possible to bypass the damaged region entirely (see graphic).

It will first be tested on rats and then monkeys.

While trials on monkeys will tell us a lot about the prosthesis's performance, there are some questions that will not be answered.

For example, it is unclear whether we have any control over what we remember. If we do, would brain implants of the future force some people to remember things they would rather forget?

"Forgetting is the most beneficial process we possess," Williams says. It enables us to deal with painful situations without actually reliving them.

Another ethical conundrum concerns consent to being given the prosthesis, says Anderson. The people most in need of it will be those with a damaged hippocampus and a reduced ability to form new memories. "If someone can't form new memories, then to what extent can they give consent to have this implant?"


  • Thanks for the information on how this brain prothesis works.

    We recently wrote an article on using the same microchip to replace a part of the brain on Brain Blogger. Would our brains reject the foreign object? How many people would evven be willing to try the chip out in the first place?

    We would like to read your comments on our article. Thank you.


    By Blogger K, at 9:01 AM  

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