Odor psychophysics in vertebrates.

The methods used to obtain psychophysical data on the nasal chemosensory systems of all classes of vertebrates are critically reviewed and a summary of the available data on their odor detection and discrimination abilities is provided. Although there are reliable methods for training at least one member of each class to respond differentially to the presence or absence of odor stimuli, very little is known about the limits of the capacity of any of the three major nasal chemosensory systems (olfactory, vomeronasal and trigeminal) to detect pure compounds. Furthermore, studies in which rigorous procedures are followed for both the maintenance of discriminative responding and the presentation of odor stimuli often fail to determine the sensory system(s) mediating the psychophysical results. This lack of information has impeded progress on several fundamental problems in the study of nasal chemoreception.