Odor-based double-alternation runway performance as a function of temporal presentation of small reward.

Abstract

Previous studies designed to investigate odor production and utilization by rat subjects have typically used doub1ealternation schedules of reward versus nonreward (i.e., RRNNRRNN, where R is a reward trial and N is a nonreward trial). More specifically, rats entering the empty goalbox of a straight runway (on N trials) appear to exude a "frustration" odor or an odor of "nonreward" which may be utilized by subsequent subjects. When these odor cues are maximized, animals are able to learn this double-alternation schedule. Without such cues . appropriate learning does not occur. The present study was designed to investigate odor production and utilization in rat subjects receiving contrasting reward magnitudes (i.e., large (L) versus small (8)). In this three-phase experiment, 14 subjects were assigned to one of two groups -Group LLSSLLSS or Group LLNNLLNN, where L is a large reward trial, S is a small reward trial, and N is a nonreward trial. To distinguish odor production from odor use, the subjects trained on the LLSSLLSS pattern preceded those trained on the LLNNLLNN pattern. As patterning failed ·to develop in Group LLSSLLSS as well as the first subject in Group LLNNLLNN, it was concluded that a discriminably different cue ("frustration" odor or odor of "nonreward") was not produced on S trials. However, shifting small-reward delivery on S trials' from the beginning to the end of the goalbox-confinement period resulted in the immediate display of patterning by the first subject in the LLNNLLNN group and the subsequent development of patterning by the LLSSLLSS subjects. Although the contrasting reward magnitudes did not influence the development. of patterning, temporal presentation of small reward did. These results may not be supportive of previous attempts designed to relate frustration theory with odor production and utilization. Specifically, receipt of small reward in a previously large-reward situation did not result in the production of "frustration" odor, even though the situation would technically be considered frustrating.