Monday, February 13, 2006

Rats smell in stereo

A recent article in Science (reviewed in the NewScientist) reports experimental results that show that rats are able to smell in stereo. In their introduction, the authors discuss two ways to localize odor sources. One is by comparing odors at different locations, much the same as one might do to locate a burning smell in a house, by moving from room to room to test for the smell. The other is by comparing simultaneous samples taken at different parts of the body. Since most animals only smell with their noses and not with their feet for instance, this mode is more unusual.

The study showed that rats are definitely able to tell which direction a smell comes from by using this stereo sense. The rats were trained to poke their tiny noses into a hole and associated odors from the left with the left water bottle and odors from the right with the right water bottle. A video shows the rat choosing the correct side 5 out of 6, (as indicated by an LED placed there just for the demonstration, caution, link loads an mpeg).

The article also mentions the need for parallel neuronal pathways which then combine for comparison, much like the two optic nerves combine when they enter the brain to produce stereo vision. Imagine being able to build a three dimensional smell model of the world just like we do with stereoscopic vision. In so far as rats think about the world around them, how might their perceptions be different from ours with the aditional overlay of the stereolfaction sense.

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