A method for establishing a five odorant identification confusion matrix task in rats

Using a cross-modal association paradigm, rats were trained to associate a particular tunnel and response location with one of five different odorants (isoamyl acetate, propyl acetate, acetic acid, phenethyl alcohol, and anethole). Each of the five tunnels differed with respect to: 1) the illuminated pattern on the response key; 2) the brightness of the illuminated pattern; and 3) the somesthetic quality of the tunnel floor. Standard operant techniques were used to train trial initiating and sampling behavior at a central odorant presentation point. Following acquisition training, the animals were tested using a standard 5 X 5 confusion matrix design. The results showed for the first time that rats are capable of performing, with a high degree of accuracy, an odorant identification confusion matrix task analogous to humans. Furthermore, using multidimensional scaling techniques, these data represent the first instance in which the perceptual odor space of an animal can be determined. With the animal model in hand, we can begin to examine how, in the presence of neural dysfunction, one odorant may be correctly identified as another.