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Starchild
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a raving alcoholic drama queen with a penchant for the biosciences
Jan 1970
time: 00:26
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19:00 12 March 03
Exclusive from New Scientist Print Edition
The world's first brain prosthesis - an artificial hippocampus - is about to be tested in California. Unlike devices like cochlear implants, which merely stimulate brain activity, this silicon chip implant will perform the same processes as the damaged part of the brain it is replacing.
Hippocampus replacement
The prosthesis will first be tested on tissue from rats' brains, and then on live animals. If all goes well, it will then be tested as a way to help people who have suffered brain damage due to stroke, epilepsy or Alzheimer's disease.
Any device that mimics the brain clearly raises ethical issues. The brain not only affects memory, but your mood, awareness and consciousness - parts of your fundamental identity, says ethicist Joel Anderson at Washington University in St Louis, Missouri.
The researchers developing the brain prosthesis see it as a test case. "If you can't do it with the hippocampus you can't do it with anything," says team leader Theodore Berger of the University of Southern California in Los Angeles. The hippocampus is the most ordered and structured part of the brain, and one of the most studied. Importantly, it is also relatively easy to test its function.
The job of the hippocampus appears to be to "encode" 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. 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.
Model, build, interface
The inventors of the prosthesis had to overcome three major hurdles. They had to devise a mathematical model of how the hippocampus performs under all possible conditions, build that model into a silicon chip, and then interface the chip with the brain.
No one understands how the hippocampus encodes information. So the team simply copied its behaviour. 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).
Memory tasks
Berger and his team have taken nearly 10 years to develop the chip. They are about to test it on slices of rat brain kept alive in cerebrospinal fluid, they will tell a neural engineering conference in Capri, Italy, next week.
"It's a very important step because it's the first time we have put all the pieces together," he says. The work was funded by the US National Science Foundation, Office of Naval Research and Defense Advanced Research Projects Agency.
If it works, the team will test the prosthesis in live rats within six months, and then in monkeys trained to carry out memory tasks. The researchers will stop part of the monkey's hippocampus working and bypass it with the chip. "The real proof will be if the animal's behaviour changes or is maintained," says Sam Deadwyler of Wake Forest University in Winston-Salem, North Carolina, who will conduct the animal trials.
The hippocampus has a similar structure in most mammals, says Deadwyler, so little will have to be changed to adapt the technology for people. But before human trials begin, the team will have to prove unequivocally that the prosthesis is safe.
Collateral damage
One drawback is that it will inevitably bypass some healthy brain tissue. But this should not affect the patient's memories, says Berger. "It would be no different from removing brain tumours," where there is always some collateral damage, says Bernard Williams, a philosopher at Britain's University of Oxford, who is an expert in personal identity.
Anderson points out that it will take time for people to accept the technology. "Initially people thought heart transplants were an abomination because they assumed that having the heart you were born with was an important part of who you are."
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?
The ethical consequences of that would be serious. "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?"
Duncan Graham-Rowe
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Richard Bruns
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NC, USA
Nov 1999
time: 06:26
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I notciced they didn´t even mention immune rejection. The body´s defenses hate solid things next to soft tissue; previous tests result in any implanted electrodes being surrounded by a gunk of immune cells that prevent connection to neurons. They´d have to keep the rat´s immune system seriously suppressed to have any hope of getting this to work, and trying it in people simply wouldn´t work, unless they were already immunosuppressed for some other reason.
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Richard Bruns
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NC, USA
Nov 1999
time: 06:26
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Of course, if you want something really scary, check this out. It is pure mind control:
quote:
Brain "pacemaker" has long-term effects on depression
A surgically implanted "pacemaker for the brain" significantly improves depression - and its benefits last for at least two years, according to the results of the first long-term follow-up study of the treatment.
Vagus nerve stimulation is conventionally used to treat severe cases of epilepsy. But after patients using the device showed notable improvement in mood, the manufacturer, Cyberonics, commissioned a pilot study of its effectiveness in depression, which was completed in 1999.
The study found that 60 people who had failed to improve after taking two or three existing anti-depression medications showed a 60 per cent improvement after surgery to implant a VNS device. However, the most treatment-resistant - those who failed on more than eight medications - did not respond to the surgery.
Two years later, the results of a follow-up study by Mark George of the Medical University of South Carolina and A. John Rush of the University of Texas Medical Center in Dallas show that those who initially responded to VNS therapy have maintained their improvements - and some of those who initially did not respond went on to report less severe depression.
Side-effects
The VNS device consists of an electrode, which is wrapped around the vagus nerve in the neck, and a pulse generator. The pulse generator is inserted into an opening in the chest. It is programmed to stimulate the nerve in 30-second bursts, sending impulses into the limbic area of the brain - an area linked to mood.
Anthony Cleare, head of the department of neurobiology of mood disorders at the UK's Institute of Psychiatry says he is still uncertain over the role VNS has in treating depression. "I don't think it will be used widely, because it requires surgery and the device is there for life. Also it has side-effects. Every five minutes the box discharges for 30 seconds, which causes the patient's voice to become hoarse," he told New Scientist.
Cyberonics is currently conducting an international double-blind clinical trial of the effectiveness of VNS for treating depression and the results are expected in spring 2002.
Cleare says: "We are just starting to evaluate the suitability of using VNS. Most people are waiting for the results of controlled trials before deciding whether to use it."
Depression is estimated to effect up to 12 per cent of men and 25 per cent of women worldwide.
The research was presented at the American College of Neuropsychopharmacology's annual meeting in Hawaii.
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It is also from New Scientist Online:
http://www.newscientist.com/news/news.jsp?id=ns99991665
The difference between this pulse generator and the hippocampus implant is that it doesn´t rely on nerve cell connections, it just delivers an electric jolt that can pass through immune cells. But it is still spooky; I didn´t know they could implant something in someone´s head that alters moods like that.
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CerberusIV
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Looking at the bonanza the legislators and lawyers (at least in the UK) have had with issues about cloning and rights to genetic information the prospect of them getting loose and ruling on the legalities of memory implants is awful!
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13-03-2003 01:23
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