Facilitative effect of a pretest exposure to the CS: Analysis and implications for the memory trace

Abstract

Retention of a brightness discrimination avoidance task by rats is impaired (Kamin effect) following a 1-h training-to-test interval (TTI), is enhanced after a 3-day TTI (reminiscence, or long-term spontaneous improvement), and is disrupted following a 21-day TTI (long-term forgetting). An exposure to the conditioned stimulus (CS), delivered 5 mm before a 1-h delayed retention test, not only compensated for the performance deficit that corresponds to the Kamin effect, but induced a large improvement in performance similar to that normally obtained after a 3-day TTI. It can be proposed that such cuing may act either by accelerating a natural memory-trace maturation process or by improving the retrievability of the memory trace. Since these possibilities lead to opposite predictions concerning the length of the facilitation induced by cuing, the effect of a pretest exposure to the CS on performance obtained during a 1-h delayed retention test was studied after several cuing-to-test intervals (0, 5, 10, or 20 min). The results, which indicate that cuing transiently enhanced subsequent retention performance, more convincingly support the retrieval hypothesis. The effects of pretest exposure to the CS (which occurred 5 min before testing) were also examined 10 min, 1 h, or 24 h after initial training. The results indicate that the facilitative effect of cuing obtained when retention performance was disrupted shortly after training (1-h TTI) was also obtained after a 24-h retention interval, in the absence of performance disruption. An interpretation of the facilitative effect of a pretest exposure to the CS is proposed, and implications concerning the memory trace are further discussed in relation to the multidimensional hypothesis. © 1990 Psychonomic Society, Inc.