Science
News
Mapping
the fruit fly brain
New
digital atlas demystifies complex neuron shapes and connections
May
8th, 2010; Vol.177 #10 (p. 16)
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A new analysis technique creates a digital neuron atlas of the
fruit fly brain, highlighting how individual brain cells link up.Hanchuan Peng
WASHINGTON
— A new computer-based technique is exploring uncharted territory in the
fruit fly brain with cell-by-cell detail that can be built into networks for a
detailed look at how neurons work together. The research may ultimately lead to
a complete master plan of the entire fly brain. Mapping the estimated 100,000
neurons in a fly brain, and seeing how they interact to control behavior, will
be a powerful tool for figuring out how the billions of neurons in the human
brain work.
The
program has already found some new features of the fruit fly brain, said study
coauthor Hanchuan Peng of the Howard Hughes Medical Institute’s Janelia
Farm Research Campus in Ashburn, Va. “We can see very beautiful and very
complicated patterns,” said Peng, who presented the results April 9 at
the 51st Annual Drosophila Research Conference. “If you look at neurons
at a better resolution, or look at regions you’ve never looked at before,
you’ll find something new.”
Peng and
his colleagues developed a method, also described in the April Nature Biotechnology,
which incorporates many different images of fruit fly brains. The brains come
from flies that were genetically programmed so that select neurons glow when
struck with a particular type of laser light. By combining thousands of these
digital images from different flies, the researchers can create maps of how
these different neuronal populations fit together. The full map of the fly
brain isn’t yet complete, but it will grow as more images are added.
These
kinds of large-scale studies that focus on how neurons are connected are
“very important for the future,” commented geneticist Wei Xie of
Southeast University in Nanjing, China. Understanding how all of the neurons
work together is much more meaningful than studying how a single brain cell
connects to another cell, Xie said. “Just a neuron is not enough.”
“What
we want to do in the next few years is to add more and more neuron
reconstructions into this map,” Peng said. He likened the process to a
Google Earth resource. “If you think about the fruit fly brain as the
Earth, the little neurons will be the streets. We want to map a lot of neuron
streets onto the Earth,” he said.
Peng and
his colleagues have started combing their preliminary brain map for interesting
features and comparing different flies’ brains to one another. For the
most part, patterns of neuron-connecting pathways don’t vary much from
brain to brain, the researchers found.
On the
other hand, the shapes of cells in the same brain structure can differ
dramatically. For example, the variety of shapes found in the neurons of a
wheel-shaped brain structure called the ellipsoid body “are just
amazing,” Peng says. In the same fly, some of the cells spread inside the
ring, while others point outward in a complex lock-and-key arrangement.
The
results are preliminary, but finding such unexpected variation could mean that
these neurons — which were thought to be nearly carbon copies of each
other — have important functional differences.