Caught on tape: Rat videos reveal whisker secrets

CHICAGO (Reuters) - Tiny twitches of their whiskers allow rats to "see" in the dark, helping them to find their way home or back to a particularly savory garbage pile.

Now, after years of trying, U.S. researchers said on Wednesday they have caught the whole thing on film, allowing them finally to understand what the rat whiskers are telling the brain.

"There is a huge amount of work but nobody really has understood what it is they are actually seeing with their whiskers," said Christopher Moore, a neuroscientist at Massachusetts Institute of Technology in Boston, whose study appears in the journal Neuron.

"For a rodent, this is the Mercedes-Benz of high-performance sensory pathways," Moore said in a telephone interview. "They can detect things with their whiskers that we can't see."

Because these tiny whisker flicks are so rapid, researchers have been unable to isolate the micro-motions that allow rats to find their way in the dark.

Jason Ritt, a researcher in Moore's lab, has been working on the problem since 2003. He painstakingly developed a high-speed video system that captures whisker movements at a rate of 3,200 frames per second, or about 100 times faster than a home video.

FAST AND FINELY TUNED

Ritt and colleagues then had to figure out how to get the rats to perform on camera. Some of the rats were trained to sweep their whiskers against a smooth surface. Others went to a rough surface. They got a sip of chocolate milk if they hit their mark.

When the researchers slowed down the video and analyzed it, they were astonished at just how finely tuned these whisker motions were. "We had no idea," Moore said.

He said the motions rats make when they touch something are up to 10 times faster than researchers had assumed. "The richness of what they are perceiving with their whiskers is far more complex than we ever would have thought."

Moore said the rat whisker system works much like the visual system in humans. "It has more kinship with the human visual system than it does with the rodent visual system," he said.

Moore said this new understanding should help guide researchers studying the brain, who often use the rat for studies that cannot be done on humans.

For example, Moore hopes to study a type of brain cell called the interneuron, which he said is fundamental to the rat's whisker system. "That same type of interneuron is exactly the one thing that is damaged in schizophrenia," he said.

Knowing how this neuron works may help researchers understand what is missing in the schizophrenic brain, he said.

(Editing by Will Dunham and Sandra Maler)