When we were children, my siblings and I spent summers in the woods of northern Canada. Sleeping in a rustic cabin, and listening to mice scamper across the rafters just above us, my fondest dream was that one of the rodents would stumble and plop right into my little sister's mouth. But for reasons I didn't appreciate at the time, she never had to contend with such an assault, even on the darkest nights. It seems that mice and rats have an unusual sensory system that works in total darkness: their whiskers. One research team is trying to unravel the workings of this hairy, touch-based system, partly in a push for better robotic sensors, and partly out of an interest in basic neurobiology.
Rats and mice "whisk" as they walk. Dozens of long hairs flank their noses, and animals rapidly sweep them forward and backward, exploring their environment the way a blind person might probe with a flexible cane. [See illustration on this page.] Rats are known to gather a remarkable amount of information about objects they whisk--remarkable because the hairs themselves are dead keratin without any sensors, just like the hairs on your head. Rats usually whisk objects in the dark at a frequency of about five to twelve hertz; that is, they sweep their whiskers back and forth between five and twelve times a second. Sensitive tissue at the base of each whisker receives the sensory information gathered in these swipes and transmits it to the brain. There, a kind of environmental map is assembled
