Decoding human brain,with a flys help

Taiwanese researchers have managed to bar code some 16,000 of the 100,000 neurons in a fruit flys brain and to reconstruct the brains wiring map.

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Taiwanese researchers have managed to bar code some 16,000 of the 100,000 neurons in a fruit flys brain and to reconstruct the brains wiring map.

In terms similar to those that define computers,the team describes the general architecture of the flys brain as composed of 41 local processing units,58 tracts that link the units to other parts of the brain,and six hubs. Biologists see this atlas of the fly brain as a first step toward understanding the human brain. Six of the chemicals that transmit messages between neurons are the same in both species. And the general structuretwo hemispheres with copious cross-linksis also similar.

I think this is the beginning of a new world, said Ralph Greenspan,a neurobiologist at the University of California,San Diego. Biologists should now be able to match the fruit flys well-studied behaviours to the brain circuits established by the new atlas,he said. The atlas is maintained on a supercomputer in Taiwan which fly biologists around the world can query.

The Taiwan team is led by Ann-Shyn Chiang,who has been working on the project for the last decade. He has assembled a group of 40 people, including computer programmers and engineers,working on a budget of about 1 million a year. The basis of the atlas is a technique for visualising the three-dimensional structure of individual neurons,including the cells nucleus,its long axon,and the little branches,or dendrites,with which it makes contact with other neurons.

The complex structure of a neuron can be made apparent with a green fluorescent protein. The gene for the protein is inserted into the fruit flys genome,along with another gene that represses it. When the gene is expressed,the green fluoprotein reaches every part of the neuron,defining its structure in exquisite detail.

Each flys brain is a different size and shape,so the team had to define average dimensions for the female and the male brain,creating a virtual brain with standard dimensions. They then developed algorithms for recasting the 3D image of each neuron so as to bring it into register with the standard brain.

Each neuron is then given a bar code with the coordinates of where its cell nucleus lies within the standard Drosophila brain. The bar codes are numerical data that can be manipulated by computer. With 16,000 images in hand,the team was able to analyse the general architecture of the female fruit flys brain.

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The fly brain turns out to be a hybrid system of grid computing and a supercomputer,. Chiang said. The fly brain,with its 100,000 neurons,may prove a better starting point for understanding the human brain,which has an estimated 100 billion neurons,each with about 1,000 synapses.

The construction of the fly and mammalian brains seems to follow the same small world principle,that of high local clustering of neurons,together with long-range connections. So theres a commonality and that has to do with the fact that these systems have to accomplish similar goals, said Olaf Sporns who designs computers of neutral circuits at Indiana University.

With a full wiring diagram of the fly brains neurons,researchers could test their ideas about how information flowed in the brain. Its not out of the question that if we had a complete cellular map and a good database,we could create virtual organisms, Sporns said.