Text 876, 107 rader
Skriven 2004-10-22 17:51:54 av Geo (1:379/45)
Ärende: Just what the doctor ordered
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From: "Geo" <georger@nls.net>

http://www.wired.com/news/medtech/0,1286,65422,00.html/wn_ascii

In this era of high-tech memory management, next in line to get that memory
upgrade isn't your computer, it's you.

Professor Theodore W. Berger, director of the Center for Neural Engineering at
the University of Southern California, is creating a silicon chip implant that
mimics the hippocampus, an area of the brain known for creating memories. If
successful, the artificial brain prosthesis could replace its biological
counterpart, enabling people who suffer from memory disorders to regain the
ability to store new memories.

And it's no longer a question of "if" but "when." The six teams involved in the
multi-laboratory effort, including USC, the University of Kentucky and Wake
Forest University, have been working together on different components of the
neural prosthetic for nearly a decade. They will present the results of their
efforts at the Society for Neuroscience's annual meeting in San Diego, which
begins Saturday.

While they haven't tested the microchip in live rats yet, their research using
slices of rat brain indicates the chip functions with 95 percent accuracy. It's
a result that's got the scientific community excited.

"It's a new direction in neural prosthesis," said Howard Eichenbaum, director
of the Laboratory of Cognitive Neurobiology at Boston University. "The Berger
enterprise is ambitious, aiming to provide a prosthesis for memory. The need is
high, because of the prevalence of memory disorder in aging and disease
associated with loss of function in the hippocampus."

Forming new long-term memories may involve such tasks as learning to recognize
a new face, or remembering a telephone number or directions to a new location.
Success depend on the proper functioning of the hippocampus. While this part of
the brain doesn't store long-term memories, it re-encodes short-term memory so
it can be stored as long-term memory.

It's the area that's often damaged as a result of head trauma, stroke, epilepsy
and neurodegenerative disorders such as Alzheimer's disease. Currently, no
clinically recognized treatments exist for a damaged hippocampus and the
accompanying memory disorders.

Berger's team began its research by studying the re-encoding process performed
by neurons in slices of rat hippocampi kept alive in nutrients. By stimulating
these neurons with randomly generated computer signals and studying the output
patterns, the group determined a set of mathematical functions that transformed
any given arbitrary input pattern in the same manner that the biological
neurons do. And according to the researchers, that's the key to the whole
issue.

"It's an impossible task to figure out what your grandmother looks like and how
I would encode that," said Berger. "We all do a lot of different things, so we
can't create a table of all the things we can possibly look at and how it's
encoded in the hippocampus. What we can do is ask, 'What kind of transformation
does the hippocampus perform?'

"If you can figure out how the inputs are transformed, then you do have a
prosthesis. Then I could put that into somebody's brain to replace it, and I
don't care what they look at -- I've replaced the damaged hippocampus with the
electronic one, and it's going to transform inputs into outputs just like the
cells of the biological hippocampus."

Dr. John J. Granacki, director of the Advanced Systems Division at USC, has
been working on translating these mathematical functions onto a microchip. The
resulting chip is meant to simulate the processing of biological neurons in the
slice of rat hippocampus: accepting electrical impulses, processing them and
then sending on the transformed signals. The researchers say the microchip is
doing exactly that, with a stunning 95 percent accuracy rate.

"If you were looking at the output right now, you wouldn't be able to tell the
difference between the biological hippocampus and the microchip hippocampus,"
Berger said. "It looks like it's working."

The team next plans to work with live rats that are moving around and learning,
and will study monkeys later. The researchers will investigate drugs or other
means that could temporarily deactivate the biological hippocampus, and implant
the microchip on the animal's head, with electrodes into its brain.

"We will attempt to adapt the artificial hippocampus to the live animal and
then show that the animal's performance -- dependent in these tasks on an
intact hippocampus -- will not be compromised when the device is in place and
we temporarily interrupt the normal function of the hippocampus," said Sam A.
Deadwyler, "thus allowing the neuro-prosthetic device to take over that normal
function." Deadwyler, a professor at Wake Forest University, is working on
measuring the hippocampal neuron activity in live rats and monkeys.

The team expects it will take two to three years to develop the mathematical
models for the hippocampus of a live, active rat and translate them onto a
microchip, and seven or eight years for a monkey. They hope to apply this
approach to clinical applications within 10 years. If everything goes well,
they anticipate seeing an artificial human hippocampus, potentially usable for
a variety of clinical disorders, in 15 years.

Overall, experts find the results promising.

"We are nowhere near applicability," said Boston University's Eichenbaum. "But
the next decade will prove whether this strategy is truly feasible."

"There is a big gap in making the microchip work in a slice preparation and
getting it to work in a human being," added Norbert Fortin, a neuroscientist
from the Cognitive Neurobiology Lab at Boston University. "However, their
approach is very methodical, and it is not unreasonable to think that in 15 to
20 years such a chip could help, to some degree, a patient who suffered from
hippocampal damage."

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