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Metal heads
The last word Metal heads John McCrone http://www.btinternet/~neuronaut
Could the neurosurgeons of tomorrow be mostly employed as hardware installers for IBM and GlaxoSmithKline? You begin to wonder when you hear of the range of neuroprosthetic and cognitive implant technology under development. There are some truly outrageous research projects about. At the University of Southern California (USC), for instance, they are talking about an artificial hippocampus. Electrode arrays slice across a rat’s hippocampus at two points to either side of a damaged region. A chip with hippocampus mimicking circuitry then attempts to bridge the gap, creating artificial pathways to restore the neural traffic. Even patching across damaged brain like this would be an impressive feat. But the researchers hope to pave the way for true memory implant devices. Alzheimer’s disease could be fixed they say. City traders might buy them as a memory upgrade allowing them to remember the details of every deal. Well, the odds against such a chip are pretty clear. But the USC team are right in saying that if neuroscientists are going to build an artificial anything then the highly regular neural architecture of the hippocampus is a good place to start. And such is the wealth of neuroprosthetics work underway, and the number of venture capital start-ups being spawned, that perhaps brain implanting could one day become as routine as pacemakers and knee-joint replacements. Deep brain stimulation (DBS) as a treatment for Parkinson’s disease is already old hat. Two other fast developing areas are implants to help the blind see and the paralysed operate computers and artificial limbs. Vision aids range from the relatively simple—a 5000 photodiode array glued to the back of the eyeball which directly converts incoming light to electrical signals and so artificially replaces receptor cells lost in retinitis pigmentosa—to a true bionic eye where a miniature camera mounted on spectacles feeds signals by a wire to electrodes embedded in the visual cortex. For vision aids, it is unclear whether it is really patient need or technological hubris that is driving the work. For even with several thousand electrodes poked into the visual cortex, all a person would see is a grainy pattern of phosphenes. As with cochlear implants, it may prove that most would prefer to remain blind rather than get stuck with the kind of distractingly unnatural visual experience that even the shiniest
444
technology is likely to provide. However the prospects look much better for implants to aid those with quadriplegia or “locked-in” syndrome. Researchers at Duke University and elsewhere have shown that even modest arrays of a few hundred electrodes can pick up enough of a signal from motor cortex areas to control a computer cursor by “thought” alone. The technological hurdles for such implants are also rapidly being overcome. Ordinary metal electrodes are too dangerous as they eventually slice up neural tissue as the brain moves inside the cranium. But the circuitry can be safely embedded in porous glass pellets. Smearing a pellet with growth factors encourages nearby neurons to sprout connections direct to it. A bigger problem is getting the signal out of the brain. But one neat solution is a skullcap that both supplies power and reads data from transmitters cemented to the scalp bone by magnetic-current induction. So, no permanently trailing wires. Such implants have a big future. It is one of the tragedies of modern medicine that improved life support systems have meant that many with diseases like amyotrophic lateral sclerosis (ALS) now live a long time, yet are unable to talk or communicate the simplest wish. Given the tenacity with which some people persevere with more rudimentary aids, such as EEG biofeedback systems that can take 10 h to generate a few hundred words, even modestly improved technology would be a boon. And there seems no reason why cortical implants could not eventually be capable of driving wheelchairs, operating light switches, and maybe even working prosthetic hands. Other gizmos are under development. Chips with micropumps that can deliver precisely timed and located doses of psychoactive chemicals could have huge application. Of course, it still seems doubtful that any of this neuroimplant technology will ever move out of a strictly clinical setting to become an everyday consumer item. I mean, who would risk a brain operation to insert hardware for cognitive enhancement? What do you do when you want to upgrade 6 months later? On the other hand, 100 years ago the thought of people subjecting themselves to major surgery to remove body fat or get a larger penis would have seemed weird beyond belief. Never say never as long as there is a willing patient and a willing doctor.
Neurology Vol 3 July 2004
http://neurology.thelancet.com
For personal use. Only reproduce with permission The Lancet Publishing Group.
Could the neurosurgeons of tomorrow be mostly employed as hardware installers for IBM and GlaxoSmithKline? You begin to wonder when you hear of the range of neuroprosthetic and cognitive implant technology under development. There are some truly outrageous research projects about. At the University of Southern California (USC), for instance, they are talking about an artificial hippocampus. Electrode arrays slice across a rat’s hippocampus at two points to either side of a damaged region. A chip with hippocampus mimicking circuitry then attempts to bridge the gap, creating artificial pathways to restore the neural traffic. Even patching across damaged brain like this would be an impressive feat. But the researchers hope to pave the way for true memory implant devices. Alzheimer’s disease could be fixed they say. City traders might buy them as a memory upgrade allowing them to remember the details of every deal. Well, the odds against such a chip are pretty clear. But the USC team are right in saying that if neuroscientists are going to build an artificial anything then the highly regular neural architecture of the hippocampus is a good place to start. And such is the wealth of neuroprosthetics work underway, and the number of venture capital start-ups being spawned, that perhaps brain implanting could one day become as routine as pacemakers and knee-joint replacements. Deep brain stimulation (DBS) as a treatment for Parkinson’s disease is already old hat. Two other fast developing areas are implants to help the blind see and the paralysed operate computers and artificial limbs. Vision aids range from the relatively simple—a 5000 photodiode array glued to the back of the eyeball which directly converts incoming light to electrical signals and so artificially replaces receptor cells lost in retinitis pigmentosa—to a true bionic eye where a miniature camera mounted on spectacles feeds signals by a wire to electrodes embedded in the visual cortex. For vision aids, it is unclear whether it is really patient need or technological hubris that is driving the work. For even with several thousand electrodes poked into the visual cortex, all a person would see is a grainy pattern of phosphenes. As with cochlear implants, it may prove that most would prefer to remain blind rather than get stuck with the kind of distractingly unnatural visual experience that even the shiniest
444
technology is likely to provide. However the prospects look much better for implants to aid those with quadriplegia or “locked-in” syndrome. Researchers at Duke University and elsewhere have shown that even modest arrays of a few hundred electrodes can pick up enough of a signal from motor cortex areas to control a computer cursor by “thought” alone. The technological hurdles for such implants are also rapidly being overcome. Ordinary metal electrodes are too dangerous as they eventually slice up neural tissue as the brain moves inside the cranium. But the circuitry can be safely embedded in porous glass pellets. Smearing a pellet with growth factors encourages nearby neurons to sprout connections direct to it. A bigger problem is getting the signal out of the brain. But one neat solution is a skullcap that both supplies power and reads data from transmitters cemented to the scalp bone by magnetic-current induction. So, no permanently trailing wires. Such implants have a big future. It is one of the tragedies of modern medicine that improved life support systems have meant that many with diseases like amyotrophic lateral sclerosis (ALS) now live a long time, yet are unable to talk or communicate the simplest wish. Given the tenacity with which some people persevere with more rudimentary aids, such as EEG biofeedback systems that can take 10 h to generate a few hundred words, even modestly improved technology would be a boon. And there seems no reason why cortical implants could not eventually be capable of driving wheelchairs, operating light switches, and maybe even working prosthetic hands. Other gizmos are under development. Chips with micropumps that can deliver precisely timed and located doses of psychoactive chemicals could have huge application. Of course, it still seems doubtful that any of this neuroimplant technology will ever move out of a strictly clinical setting to become an everyday consumer item. I mean, who would risk a brain operation to insert hardware for cognitive enhancement? What do you do when you want to upgrade 6 months later? On the other hand, 100 years ago the thought of people subjecting themselves to major surgery to remove body fat or get a larger penis would have seemed weird beyond belief. Never say never as long as there is a willing patient and a willing doctor.
Neurology Vol 3 July 2004
http://neurology.thelancet.com
For personal use. Only reproduce with permission The Lancet Publishing Group.