The junctions between neurons and other nerve cells in the brain (what are called synapses) form networks that can be quite large in order for the brain to process a multitude of tasks.

However, in some cases only a few neurons could be used to perform a simple task.

Howard Hughes Medical Institute researcher Karel Svoboda, a leader of one of the studies, stated, “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. But it turns out that a remarkably small number—on the order of 50 or so activated neurons—is sufficient to drive reliable behaviors." [U.S. News and World Report “Brain Cells More Powerful Than You Think”]

The Svoboda study has been written up in the December 20, 2007 issue of Nature. Specifically, within their experiment, the Svoboda team, which consists of Daniel Huber and colleagues at the Janelia Farm Research Campus, Virginia, and Cold Spring Harbor Laboratory, New York, used mice to show that less than fifty brain cells were needed in order to react to a light stimulus.

They stated that while a mouse reacts to the light, its brain is also dealing with a hundred thousand or so electrical signals that are producing other activities. In humans, a trillion or so signals are being constantly produced.

The study also found that as electric impulses travel between neurons they strengthen the connection (synapse) between those two neurons. Even more important, electrical impulses also strengthen the synapses between neighboring neurons. This strengthening action helps the brain to learn faster and better.

Svoboda says that such action had been predicted by previous medical studies, but had not been previously proven. In order to accomplish this task, Svoboda’s team used a highly precise technique to guide a laser deep within the memory portion of the mouse’s brain. With this knowledge, Svoboda’s team contends that such action may be the mechanism by which memory is created and enhanced.

The information learned from the Svoboda study, and other similar studies, could help the scientific world learn how the brain organizes information, how it learns and remembers things, and how it breaks down sometimes and forgets things.

Additional information about the small number of neurons needed for the brain to act is found in the Telegraph article “Why you are cleverer and simpler than thought.”

More information about the synapses connection to memory is provided in the Scientific American article “Signaling Neurons Make Neighbor Cells ‘Want In’.”


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