From the twitching whiskers of babes: Naptime behavior shapes the brain

"We found that even whiskers twitch during sleep—and they do so in infant rats long before they move their whiskers in the coordinated fashion known as whisking," said Mark Blumberg of The University of Iowa. "This discovery opens up new avenues for investigating how we develop critical connections between the sensors in our body and the parts of the brain that interpret and organize sensory information."

In fact, the baby rats' whiskers don't just twitch, they twitch very rapidly and in complex ways. Those twitches during sleep are tied to bursts of activity in the brain, which aren't often observed when rats are awake.

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Sample video clips of individual, dual, and multiple whisker twitches are shown, as is an example of a mystacial pad movement. See Figure 1A to orient the whiskers on the snout and to identify each of the 11 whiskers and Figure 1B for the associated quiver plots. Each clip was recorded at 200 frames/s and is played back at 50 frames/s. The white light in the lower-right-hand corner indicates that the experimenter observed twitching of the distal limbs or tail, indicative of active sleep. Note that these clips only show those 11 whiskers that were monitored in these tests. Credit: Current Biology, Tiriac et al.

Other parts of the body twitch spontaneously during sleep, too, including the eyes (think "rapid eye movements") and the limbs. "Spontaneous motor activity can play many different roles in early development and even throughout life," Blumberg explains. "It can be a source of brain activity in general as well as a source of highly specific, patterned activity that can help shape specific neural circuits."

But no one had given much thought to this activity in the very special case of whiskers, which are as important to rats as eyes are to humans. Each individual whisker maps to discrete regions of the brain that process information from that individual whisker alone. The whisker-specific brain regions form arrangements that map beautifully to the physical arrangements of whiskers on the snout.

That precise organization has made the study of whiskers very popular amongst neuroscientists seeking a basic understanding of the developmental mechanisms linking peripheral sensors and brain, and that's what makes this new discovery all the more intriguing. It might also give us a new appreciation for the important work infants are doing even as they sleep.

"One of the jobs of the infant is to learn how all the parts of the body function even as those parts are growing in size and proportion," Blumberg says. "It is a difficult job."

More information: Tiriac et al.: "Rapid whisker movements in sleeping newborn rats." DOI:10.1016/j.cub.2012.09.009

Journal reference: Current Biology

Provided by Cell Press