Navigation Links
Brain Cells More Powerful Than You Think

Even single neurons have a big impact on behavior, studies show

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.

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.

Finally, they adjusted the amount of light downward until they found the lowest number of brain cells needed to evoke a measurable response in the mice. That number turned out to be less than 50 -- much fewer than the wide-flung networks of cellular activation neuroscientists had previously assumed would be necessary, Svoboda said.

The mouse brain's ability to tap into a mere 50 cells is even more remarkable when you consider that the activity of this cluster of cells takes place amid a background roar of other neurological "noise" from millions of cells, he said.

"At the same time, the functional brain area just chatters along and produces perhaps a hundred thousand spontaneous action potentials [electrical signals]," he noted. "So, the brain can actually distinguish the tiny, tiny number of action potentials from that huge background."

According to Svoboda, the experiment strongly supports a theory of brain function called "sparse coding," in which "neurons that listen to the neurons that we have activated have to be able to pull out very sparse subsets of activity."

In another study, Svoboda and co-researcher Christopher Harvey, also of the HHMI and Cold Spring Harbor Laboratory, focused on the synapse -- the microscopic gap separating individual neurons. Messages are passed neuron-to-neuron across the synapse by a complex mechanism of electrochemical signaling.

"Scientists had shown that synapses behave rather independently," Svoboda said, so that long-term electrical activation ("potentiation") of one synapse didn't directly affect a neighboring synapse. Long-term potentiation is, in essence, the key cellular step in how the brain lays down memory.

However, computer models had suggested that activation at one synapse might more subtly strengthen the synapses around it. In their experiments, Svoboda and Harvey found this to be true.

They report that "neighborhoods" of 10 or 20 synapses "influence each other cooperatively," strengthening discrete groups of synapses.

What's more, this type of synaptic teamwork happens within a specific time-frame -- about 10 minutes, a perfect amount of time for laying down the kinds of memories that can lead to learning, Svoboda said.

"That's a very behavioral timescale for learning and memory," he said. For example, a mouse can be placed in a chamber, explore it for a few minutes, then be removed from the chamber and yet retain a working memory of that chamber once it has been reintroduced to it.

That's probably due to the fact that the mouse's brain formed synaptic clusters (i.e., memory) specific to the new chamber while it was exploring it, Svoboda explained.

"In this way, they can be dissociated [from the stimulus] over several minutes but still lead to learning," he said.

While many of these experiments were done in mice, the human brain should work similarly, albeit on a much larger scale, Svoboda said. While the mouse brain contains about 100 million neurons, human brains top out at a trillion such cells, he said.

And even though the research looked at healthy brain function, it may have implications for research into aging or diseased brains, as well.

"You need to understand the fundamental mechanisms. Then you can gain better insight into what might go wrong during neurodevelopmental and neurodegenerative disorders," Svoboda said.

Sanberg agreed.

"This work clearly shows us that all cells are important, and we should try and maintain and keep as many brain cells as possible," he said. "But the number is always flexible and, as you can see, even one cell can influence a number of others."

More information

Learn more about the human brain at The Franklin Institute.

SOURCES: Karel Svoboda, Ph.D., Group Leader, Howard Hughes Medical Institute, Ashburn, Va., and Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y.; Paul Sanberg, Ph.D., distinguished university professor and director, Center of Excellence for Aging and Brain Repair, University of South Florida College of Medicine, Tampa; Dec. 20, 2007, Nature

Copyright©2007 ScoutNews,LLC.
All rights reserved  

Related medicine news :

1. Draining away brains toxic protein to stop Alzheimers
2. Vision restoration therapy shown to improve brain activity in brain injured patients
3. Clinical depression linked to abnormal emotional brain circuits
4. Brain imaging reveals breakdown of normal emotional processing
5. Brain cells work differently than previously thought
6. Vaccine Stops Alzheimers Brain Tangles
7. Research may unlock mystery of autisms origin in the brain
8. Scientists Spot Brains Free Will Center
9. Free will takes flight: how our brains respond to an approaching menace
10. Alcoholics With Cirrhosis Have More Brain Damage
11. Brain Lesions Predict MS Progression
Post Your Comments:
Related Image:
Brain Cells More Powerful Than You Think
(Date:11/24/2015)... ... November 24, 2015 , ... All her life, Don Peck’s mother wondered if she was ... she might have been. After a 25-year search for information, Don and his aunt ... shared a last name. Turns out, it was Don’s father who was descended from ...
(Date:11/24/2015)... Pass, OR (PRWEB) , ... November 24, 2015 , ... ... Lose too much body water to perspiration in the hot sun, and heat stroke ... to Fresh water advocate and radio host Sharon Kleyne. Every cell, system and structure ...
(Date:11/24/2015)... ... 2015 , ... The OSHA Training Center at Chabot-Las ... in Northern California, is calling on retail employers to implement safety measures to ... volume of sales and shoppers rapidly expands, retailers are strongly encouraged to develop ...
(Date:11/24/2015)... Miami, Fl (PRWEB) , ... November 24, 2015 , ... ... Farms. Adding houseplants is an easy and affordable way to bring long-lasting style and ... “green heroes” also provide oxygen, clean the air and keep on giving all year ...
(Date:11/24/2015)... (PRWEB) , ... November 24, 2015 , ... Take the audience on a journey with ... 3D camera path through a cloud of images without ever setting a single keyframe in ... the Inspector Window. Then use the controls to change the angle and depth of field ...
Breaking Medicine News(10 mins):
(Date:11/24/2015)... Nov. 24, 2015  Ascendant Solutions, Inc. (Pink Sheets: ... Board of Directors has declared a special 1 percent stock ... is payable December 14, 2015, to shareholders of record December ... of additional shares of common stock. ... is a strong endorsement of our confidence in Ascendant,s growth ...
(Date:11/24/2015)... st  Scientific Assembly and Annual Meeting of ... taking place in Chicago on Nov-29 th ... --> st  Scientific Assembly and Annual Meeting of the Radiological ... in Chicago on Nov-29 th through ... Molecular Dynamics will present its revolutionary whole body CZT digital SPECT/CT ...
(Date:11/24/2015)... November 24, 2015 --> ... Inhibitors, MTTP Inhibitors, ApoB Inhibitors and PPAR Agonists ... to grow at the fastest rates? This visiongain ... data, trends, opportunities and prospects there. ,  ,Our 199-page ... most lucrative areas in the industry and the future ...
Breaking Medicine Technology: