Unpredictable/uncontrollable stress proactively interferes with appetitive Pavlovian conditioning

Abstract

Prior research on the proactive effects of exposure to uncontrollable aversive events has demonstrated interference with the formation of S-S associations. However, given a variety of interpretational problems, the basic mechanism responsible for such transfer requires further examination. In order to avoid some of these problems, the present study investigated whether such an interference effect could be observed on an appetitive Pavlovian discrimination task (i.e., A+ AB− ). Furthermore, the unpredictability of stress was manipulated by means of an external feedback stimulus in order to gain a better understanding of the mechanism underlying any transfer observed. After stress exposure, animals showed equivalent acquisition of an excitatory association to a tone consistently paired with a food US (i.e., A+) during the first phase of conditioning. During the appetitive Pavlovian discrimination phase, the group exposed to uncontrollable and unpredictable shock showed retarded acquisition of the Pavlovian discrimination. However, the group exposed to uncontrollable stress accompanied by a feedback stimulus (i.e., predictable stress) did not show interference. This pattern suggests that the transfer observed may result from learning about S-S independence during the original stress exposure. Thus, this outcome may be most easily integrated with a general learned irrelevance view.