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Rats Smell... in Stereo

Rats zero in on a whiff of banana oil and other scents with the help of a stereo processing system that takes in differences in smell intensity and the time that the smell arrives in each nostril, a process that is similar to the stereo processing of sounds, reports Science.

Rat sniffing.

Rat licking water spout
Rat licking water spout.

Download video of the 6 trials performed by one of the rats. A video camera was placed in front of the sniff port and the performance of the rat was recorded at 25 frames/second.

Two air streams were delivered continuously from either side of the sniff port, and odor was added to one of the air streams for each trial. The rat was supposed to lick the left water spout if the odor came to the left, and lick on the right if the odor came to the right. One of the odor tubes is visible on the right side.

The two light emitting diodes (LEDs) mounted on the side indicate time and side of odor onset. These LEDs were placed there only for this video and were not present during the experimental method. In this video, the rat performed 6 trials, and made a mistake only on the second trial.

Photos and video courtesy of Science.

In the olfactory bulb of the rat brain, 90 percent of the neurons respond differently to smells coming from the left and right sides of the rat, Raghav Rajan and colleagues from India discovered. The researchers trained rats to lick different water spouts after taking a quick sniff of their surroundings to indicate whether a piped-in scent came from their right or left sides. The rats usually needed only one sniff, processed in 50 milliseconds, to determine the direction of the smell.

For rats, Rajan and colleagues say, “each sniff is a perceptually complete snapshot of the olfactory world, including both odor identity and stereo-based location.”

2 February 2006


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