It's no secret that rats which spend much of their lives navigating narrow, often lightless passages need more than a good sense of smell to get around. They also need a sense of touch, and it's their whiskers that do most of that work for them. What researchers never knew was precisely how elaborate that tactile system is, nor exactly how it operates. But in research that will be published in the Feb. 28 issue of Neuron, investigators at MIT have come up with an imaginative tool for finding out: high-speed video technology that works at 3,200 frames per second approximately 100 times faster than home video. "There were hypotheses before," says Christopher Moore, member of the McGovern Institute for Brain Research at MIT and senior author of the study. "But now we can actually see how these whiskers work and what they are sensing."
Scientists already knew that similar to the way a fingertip moves across a surface, the 50 or so hairs on a rat's cheek vibrate against an object to perceive its shape and texture. The video technology revealed the fluid micromotions of the whiskers, which send signals to the brain where they're interpreted as a sensory experience. What's more, the scientists were also able to study how different kinds of whiskers transmit different kinds of sensations. Short hairs, which are located on the front of the snout, transmit higher frequencies and vibrate fastest, while longer whiskers, which are further back, move slower and transmit lower frequencies. Says Moore: "They behave like the strings on a harp."
Since rats are used in many laboratory experiments and their whiskers function in a similar way to the human sense of touch, it is important to understand how they perceive objects and sense surfaces. "Most of modern biology is based on studying rodents," says Moore. "It is crucial to understand them." While MIT's research has figured out much of the unknown about the mechanics of the rats' whiskers, future research still needs to be done to understand how their brains actually decode and interprets the information.