New tool may illuminate brain's inner workings.
European researchers have developed a new tool for studying nerve
cells in the brain. The implanted tool can simultaneously inject fluid
into individual cells, shine light on them, and record their electrical
activity.
Stieglitz's team is one of several participating in the new field
of optogenetics. It involves inserting genes from certain types of algae
into other organisms, such as mice, to make the cells of those
organisms responsive to light. Scientists can then influence the cells'
electrical activity in a controlled manner by shining pulses of
different colors of laser light onto them.
"We also plan to have better integration of connectors to light,
electrical plugs, and fluids to provide superior handling properties and
to allow for use in really freely moving animals," said Stieglitz.
-Peter Gwynne, Inside Science News Service
A former science editor of Newsweek, Peter Gwynne is a freelance science writer based in Sandwich, Massachusetts.
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The researchers demonstrated the value of the device, called an
optrode, in experiments on mice. Laser pulses allowed them to influence
the activity of nerve cells in the rodents' brains in a controlled
manner.
"Proof of concept has been achieved," said Thomas Stieglitz, of the
Laboratory for Biomedical Microtechnology at the University of Freiburg
in Germany.
The team reported that its implant was the first multiple-use
device to record the activity of single brain cells onto which it had
transmitted light.
The team used a technique called transfection to insert genetic
material from one organism into another. The optrode monitors the
transfected cells for electrical activity as well as providing a channel
for the laser light.
This new technology "has the potential to revolutionize the fields
of neuroscience and neuroprosthetics," the researchers reported earlier
this year in the journal Lab on a Chip.
"Optogenetics facilitates the science of investigating the behavior
of nerve cells and fundamental research to better understand neural
networks and brain behavior," said Stieglitz. "Scientists can use
optogenetic experiments to study brain behavior and function – in
anxiety disorders, for example."
Scientists and engineers from Freiburg and the Friedrich Miescher
Institute for Biomedical Research in Basel, Switzerland, worked together
to create the device.
"Scientists need knowledge of genetic engineering to design
'shuttles' – the so-called vectors – for nerve cell transfection. This
is the job of biologists," said Stieglitz. "In addition, engineers are
sometimes asked to develop tools to optically stimulate the transfected
cells and to record electrical nerve activity. The challenge is to
develop the optrodes that combine electrical and optical activity."
One broad area where the device may be used is improving
understanding of anxiety, depression, and motivation. Stieglitz's group
aims to do that by applying its technology to networks of cells in the
hippocampus, the part of the brain responsible for memory, and nuclei,
which show up as gray matter. They will carry out the research in
experimental animals.
"We will transfect cells that are candidates to malfunction in
these disorders, and perform studies to modulate cell behavior by
optical stimulation to understand the fundamental mechanisms," said
Stieglitz.
The device, unlike current tools in optogenetics, combines all the
required components into a single, self-contained device. This means
only a single surgery is needed to implant the probe in an experimental
animal, unlike some optogenetic devices, which require multiple
surgeries.
The material that the team used to create the probe confers other advantages.
"It is made out of polymers only, plus a little bit of thin-film
metal," said Stieglitz. "Polymers are more flexible than silicon in
general and can follow the movements of the brain better because of that
flexibility."
Previous studies had established the safety of the polymers for use in implantation in the nervous system.
David Lyon, assistant professor of anatomy and neuroscience at the
University of California, Irvine School of Medicine, pointed out another
advance achieved by the device. "A novel feature is the mechanism for
delivering fluids through the chronically implanted optrode," said Lyon.
"The fluidic channel allows precise injection of the vector-carrying fluid," said Stieglitz.
The device also has the advantage of minute size. Its tip is only a
quarter of a millimeter wide and a one-tenth of a millimeter thick.
However, Lyon, who is starting up an optogenetic research group,
pointed out one disadvantage of the new optrode: It needs to be
implanted semi-permanently to be most effective.
"You don't want an implant in the brain for several weeks," Lyon said.
The risk is that the implant can influence brain activity by its presence over a period of time.
One of the Freiberg-Basel team's goals for a second version of its
optrode is an injection channel that dissolves over time. That would
reduce the probe's size significantly.
-Peter Gwynne, Inside Science News Service
A former science editor of Newsweek, Peter Gwynne is a freelance science writer based in Sandwich, Massachusetts.
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