In nature, rodents are afraid of cats when they smelled their presence. But this may be a thing in the past as scientist found how to genetically erase the mice's phobia! Scientist at the University of Tokyo used genetic engineering to successfully switch off a mice instinct to run at the presence of cats. This new method shattered common believes that fear is learned through experience.

Mice are naturally terrified of cats and usually panic or flee at the moment they smelt its presence. Humans will shy away at certain smell too, we are born with a dislike of curdled and moldy food and when we detect rotten food we will distance ourselves from the smell instinctively. The findings suggest that the human aversion to dangerous smells could also be genetically predetermined, according to research leader Ko Kobayakawa.

The genetic surgery had only affected the nerve cells in the nose (dorsal zone olfactory sensory neurons) that can trigger fear, but they did not lose the feeling of fear entirely. They found that the altered mice still froze if they heard a cat meow. "This observation may suggest that the mice only lacked the innate fear responses to cats' odors, but they did not lose the feeling of fear," said Dr Kobayakawa.

The technique has great potential in neuroscience, he said "We think it as the power to clarify many unrevealed principles of the brain, those which generate emotions and behaviors in mammals." There is increasing evidence that humans do respond to the smell of signaling chemicals - pheromones, - added Dr Denise Chen, of Rice University, Houston. "Only a few years ago, many in the scientific community would not even entertain the idea of a human pheromone.

"The past couple of years have witnessed a paradigm shift in this belief, as a result of an explosion of findings about the involvement of the main olfactory system in pheromone sensing." The idea of the presence of both learned and innate systems for processing smells within the main olfactory system may shed light on understanding and elucidating the differences in which humans process salient social chemo signals (for example, fearful sweat) and other types of smells (for example, non-emotional body odor or non-social smells)."

Source : news.nationalgeographic.com
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