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Neurons with a Sixth Sense

When rats are touched at their facial whiskers, nerve cells in the brain become active even before the contact is made, Berlin researchers report (March 2015).

Conspecific or rat trap? To answer this question, rats use their whiskers, or vibrissae. With their help, they can perceive different objects and textures even in the dark. In this process, each whisker sends information to nerve cells in the primary sensory brain area: the so-called barrel cortex. Scientists at the Bernstein Center Berlin and the Humboldt-Universität in Berlin now show that neurons in the barrel cortex recognize touch even before actual physical contact.

“In our study, we measured the electrical potential that exists across the cell membrane of brain cells. It is the basis for the transmission of signals and virtually establishes the “language” of nerve cells,” explains first author Constanze Lenschow. “When we examined the membrane potential while striking the vibrissae, we discovered: the potential starts to fluctuate prior to the actual touch. This basically means: the nerve cells begin to talk before they know the topic of the conversation.” This finding stands in contrast to the idea that the barrel cortex simply represents touch information. The neurobiologists suggest that the brain area processes other sensory stimuli as well.

“Socially induced sniffing of the rat might be responsible for the pre-touch activity in the barrel cortex,” says lead author Michael Brecht. It is also conceivable that odors in the form of pheromones or acoustic sounds emitted by the rodents in the ultrasonic range play a role. This hypothesis is supported by the fact that contact with conspecifics and non-conspecific causes different effects.

“When the vibrissae are touched by another rat, there are much larger membrane potential fluctuations than when they are struck by a stuffed rat or the hand of the experimenter,” Lenschow reports. Until now, little was known about how the whisker-to-barrel system processes biologically meaningful information, such as social contact. The result of the scientists indicates a difference between simple and complex social stimuli. An important finding for the research field: so far, many studies have examined the role of the barrel cortex using artificial stimuli to stimulate the whiskers. The result of the current study is published in the journal Neuron.

Nervenzellen mit sechstem Sinn_image_25-03-15

Rats use their whiskers to orientate themselves. In the study, the researchers recorded the membrane potential (Vm) of single nerve cells while the animals interact with their environment. There are much larger membrane potential fluctuations when the animals interact with a living conspecific (A) than with a stuffed rat (B).
Copyright (including icon): Evgeny Bobrov, 2015

 


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Prof. Dr. Michael Brecht
Bernstein Center Berlin
Humboldt-Universität zu Berlin
Philippstr. 13, House 6

Tel: +49 (0)30 2093 6718
Email: michael.brecht@bccn-berlin.de







C. Lenschow & M. Brecht (2015): Barrel cortex membrane potential dynamics in social touch. Neuron, 85(4), 718 – 725.
doi: 10.1016/j.neuron.2014.12.059