Fearless Mice
Eric Dover, 30/04/2009
Researchers at the University of Tokyo have discovered that there are different smell pathways to the brain for innate and learned fear and that they are both controlled by the olfactory neurons in the epithelium of the nose and the bulb of the brain. Discovered in mice, the researchers changed several of the genes in the olfactory bulb so that several of its functions were disabled. This means that the mice not only were not afraid of bad things such as cats and rotten food, but they also showed little interest in other mice and good food.
There are two regions of the olfactory epithelium, the dorsal and ventral and until now no one knew what the difference was between them in how the brain experienced smell. It is now known that the dorsal region controls innate fear responses and the ventral controls learned aversion.
This is helping scientists to explain how odours are translated into actions; this was shown with the mice again. Usually when mouse smells a fox the brain is stimulated to release adrenocorticotropic hormone, which is a sign of stress, however the fearless mice released no such hormone.
Reference: http://www.nature.com/news/2007/071107/full/news.2007.224.html
Additional: http://www.pinktentacle.com/2007/11/scientists-create-fearless-mouse/
