Postacquisition unexpected footshock disrupts appetitively motivated instrumental performance based on short-term retention

Abstract

Water-deprived rats were trained to run for water in an E-maze on a delayed-alternation task with a 5-min retention interval. Each day, long before encountering and again long after having encountered the delayed-alternation task, all subjects consistently experienced weak footshock in Context A and no footshock in Context B. Contexts A and B were highly dissimilar to each other and to the E-maze. On delayed-alternation probe trials, subjects were exposed to Context A or Context B for the middle 30 sec of the delayed-alternation retention interval. Performance on these trials was unaffected when weak footshock occurred in Context A or no footshock occurred in Context B. However, when weak footshock occurred in Context B, retention was impaired. An absence of footshocks in Context A produced a nonsignificant tendency towards impairment. Thus, the disruptive effects of unexpected events that occur during the retention interval do not appear to depend upon the target and unexpected events’ having similar reinforcers or even having reinforcers of the same valence. The results are interpreted in terms of unexpected events’ recruiting more of the limited information-processing capacity of the subject than do otherwise similar expected events. Moreover, the tendency of unexpected shock to interfere with performance more than does unexpected nonshock suggests that the degree to which an unexpected event recruits processing capacity depends on the affective value of the event as well as on its unexpectedness.