Common and unique components of reward and frustrative nonreward odor emissions in the rat

Abstract

Evidence for the production of differential odors by laboratory rats exposed to rewarded and nonrewarded goal events has been accumulating in recent years. While studies have shown that the odors arising from these treatments are discriminable by conspecifics introduced into the treatment environment, attempts to transfer the odors on paper flooring collected from the treatment area have not been particularly successful in achieving discriminations by conspecifics. The present studies were designed to provide data bearing on this discrepancy, and, in the process, bring data to bear on the common and differential components and volatile properties of the odors emitted by rats receiving the rewarded and nonrewarded treatments. To aid in the investigation of these odors, an olfactometer was developed which permitted the administration of rewarded and nonrewarded placements to odor-donor rats in small compartments through which filtered air could be passed, thereby transporting available olfactory components to test rats. In conjuction with the olfactometer, the appropriateness of an operant-discrimination task and procedure were examined as a means of drawing inferences about the discriminable properties of the odors from the behavior of the test rats. The results of four experiments suggest that paper flooring collected from the treatment area where donors received reward or nonreward carries rat-odor components which are common to rewarded and nonrewarded treatments. In contrast, odor cues collected by passing air over the donors or through the compartments after removing the donors are treatment unique and readily discriminable from one another. Tests performed with various rat, non-rat, and food odors indicated that the treatment-unique components which controlled discrimination in the test rats were provided by the donor rats themselves, and were highly volatile relative to other rat-odor components which were common to the treatments. The operant-discrimination task employed yielded substantial and reliable differential rates of responding by the test rats, with no obvious constraints on the ability of test rats to utilize either reward or nonreward odors as discriminative cues. Likewise, the olfactometer provided an effective means of trapping and transporting sufficient quantities of the volatile-and-differential odor components produced by donors receiving the rewarded and nonrewarded treatments.