Just as pushing over one domino can topple a line of others, charging one neuron can activate millions of cells in the brain, UC Berkeley researchers found in a recent study.

In the study, published last week in Science Magazine, researchers at a campus lab were able to change brain activity in rats by rapidly firing an electrical charge at one neuron, showing that one cell can change the entire state of the brain.

Through their findings, scientists are able to understand more about how the brain is wired, said Cheng-yu Li, UC Berkeley postdoctoral fellow in the Helen Wills Institute of Neuroscience and the department of molecular and cell biology.

"The novelty of this phenomenon is manipulating a single cell switches the brain state from one stage to another," said Li, who was the first author of the study.

To monitor brain activity for the experiment, researchers anesthetized rats so the rats would lose consciousness but their brain activity could still be viewed.

Scientists had hoped to model brain activity during sleep, when the brain switches from slow wave patterns to periods of rapid eye movement known as REM sleep.

When they charged the cell, they found that the brain switched from producing slow brain waves to producing brain waves that fluctuated rapidly. These rapid brain waves are typical of periods of REM sleep, which is often associated with dreams.

Yang Dan, a UC Berkeley professor of neurobiology who worked on the study, said researchers did not expect to find that the brain changed in response to charging a single cell.

"The real surprise is a single neuron activity can change the brain activity globally," she said. "We used to think one neuron doesn't matter that much, but this study shows that if you drive that neuron really hard that can have a surprisingly big effect."

By studying the rats' brains under anesthesia, Li and his colleagues found that charging a brain cell changed the state of the brain 40 percent of the time, which they said was a significant correlation.

Li said scientists working on this study plan to look deeper into the mechanisms of how one neuron can activate nearby neurons until millions of other cells in the brain are activated as well. Their next study will involve injecting dye into the brains of rats to follow the path of a signal from one neuron to the next.

"We are looking at what the mechanisms (are in this process) by using calcium dye imaging to look at other cell activity in the cortex," Li said.

Craig Heller, a biology professor at Stanford University, said the study shows that the brain is able to process a large volume of information at one time because it can pick up the little details.

"It is really interesting that a single cell can result in a cascade of events that alert or activate the cortex," he said.

Tags: NEUROSCIENCE