February 28, 2008

Whiskers Allow Animals to “˜See in the Dark’

Scientists at the Massachusetts Institute of Technology (MIT) in Boston believe they have discovered how whiskers communicate with the brain.

The researchers performed their study with rats, and said the tiny twitches the whiskers make effectively allow the rats to "see" in the dark.  

To study the movements, the team worked over the course of several years to develop a high-speed video system that captured the whisker movements 100 times faster than home video, at a rate of 3,200 frames per second.

"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, the study's co-author and a neuroscientist at MIT, in a telephone interview with Reuters.

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

Because these tiny whisker flicks occur so rapidly, researchers have been for years unable to isolate the micro-motions that allow rats to find their way in the dark.  But the new video provided a way to finally solve the puzzle.

Jason Ritt, a researcher in Moore's lab, had been working on the problem since 2003 and developed the new video system. However,  Ritt and his colleagues then had to get the rats to perform on camera.

Some of the rats were trained to sweep their whiskers against a smooth surface, while others went to a rough surface. The rats were rewarded with a sip of chocolate milk whenever they hit their mark.

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

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

Moore explained the rat whisker system works very similar to 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 believes the study's results will help guide researchers studying the brain, who often use the rat for studies that cannot be performed with humans.  He hopes to study a type of brain cell called the interneuron, which 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.

Studying how this neuron works could help researchers gain a better understanding of the schizophrenic brain, he said.


Video: High-speed videography, developed by MIT researchers, reveals how a rat uses its whiskers to explore a textured surface. An automated algorithm is used to analyze the whisker micromotions, which are thought to underlie rats' highly developed abilities to perceive tactile objects and distinguish textures.  This video was captured at 3202 frames per second, so on most computers the playback will be slowed down by about 100x. Watch This Video Now


Photo Caption: This frame from a time-lapse movie shows multiple traces (red) of a single rat whisker, captured at 3,200 frames per second, as it moves from left to right across a rough surface and then a smoother one. (For clarity, only every 3rd trace is shown, or about one per millisecond). Clusters and gaps of the traces correspond to this whisker's rapid sticking and slipping movements during ~175 milliseconds of surface contact. The lower end of the whisker trace corresponds to the rat's face, which moves closer as it encounters a change from rough to smooth texture. Image courtesy / Jason Ritt, McGovern Institute for Brain Research at MIT


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Massachusetts Institute of Technology

The study appears in the journal Neuron.  An abstract of the report can be viewed here.