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WEDNESDAY, Dec. 19 (HealthDay News) -- The human brain constantly sorts through its 1 trillion cells, looking for perhaps only one or a handful of neurons to carry out a particular action, a trio of new studies says.
The research, conducted with rodents and published in the Dec. 20 issue of Nature, could rewrite the textbooks on just how important individual brain cells or cell clusters are to the working mind.
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Before these insights, "The thinking was that very large ensembles of neurons [brain cells] had to be activated at some point for the animal to feel or perceive" a stimulus, explained the senior researcher of two of the studies, Karel Svoboda, a group leader at the Howard Hughes Medical Institute in Ashburn, Va.
"But it turns out that a remarkably small number -- on the order of 50 or so activated neurons -- is sufficient to drive reliable behaviors," said Svoboda, who is also associated with the Cold Spring Harbor Laboratory, in New York.
Another study, this one conducted by scientists at Humboldt University Berlin and Erasmus Medical Center in Rotterdam, the Netherlands, found that stimulating just one out of the estimated 100 million neurons in a rat's brain was enough to cause the rodent to act differently.
"The fact that a single cell can influence behavior in the cortex is fascinating," said neuroscientist Paul Sanberg, director of the Center for Excellence for Aging and Brain Repair at the University of South Florida, Tampa. The new findings are "allowing us to answer questions about how the brain controls behavior at the cellular level," added Sanberg, who was not involved in the studies.
In one of the studies, Svoboda and his colleagues genetically engineered a select few brain cells in active mice so that the cells would react to a light stimulus.
Then they exposed a part of the rodent's brain and placed a small light-emitting diode over the area. The experiment "was essentially a trick to stimulate [only] these cells," Svoboda explained.
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