Neuroscientists today know a lot about how individual neurons operate but remarkably little about how large numbers of them work together to produce thoughts, feelings and behavior. What is needed is a wiring diagram for the brain—known as a connectome—to identify the circuits that underlie brain functions. The challenge is dizzying: There are around 100 billion neurons in the human brain, which can each make thousands of connections, or synapses, making potentially hundreds of trillions of connections.
So far, researchers have typically used microscopes to visualize neural connections, but this is laborious and expensive work. Now in a paper published March 28 in Nature, an innovative brain-mapping technique developed at Cold Spring Harbor Laboratory (CSHL) has been used to trace the connections emanating from hundreds of neurons in the main visual area of the mouse cortex, the brain’s outer layer.
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Perhaps most important, the technology may help in understanding neuro-developmental disorders like autism and schizophrenia. Some theories assume brain wiring goes awry during development in these conditions, especially in autism. Whereas MAPseq cannot be used in humans (who do not like to be genetically tinkered with), numerous animal models could be studied. Many such models of autism reproduce symptoms by mimicking genetic mutations linked to the human condition. One possibility is that the huge diversity of autism-linked mutations may all point to common wiring defects. “If we could find that, we might have a handle to understand the condition and maybe do something about it genetically,” Kebschull says. “We’re starting to work on that in the lab now.”
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