COHERENCE OF RETRIEVAL CUES, RATHER THAN ADDITIVITY, DETERMINES PRIOR CUEING EFFECTIVENESS IN THE RAT

In previous studies, we have shown that adding a supplementary cue in a prior-cuing treatment may dramatically reduce its initial effectiveness. This series of experiments was aimed at testing the hypothesis that such a lack of additivity among retrieval cues could be due to the combined reactivation of memory attributes related to incompatible behavioral responses. For that purpose, rats were partially trained to reach the lighted arm (light condition; usual training condition) or the darkened arm (dark condition) of a Y-maze in order to avoid an electric footshock. The first experiment demonstrates that animals learned the two versions of the task similarly and that an exposure to the light similarly acts as an effective retrieval cue after a 24-h interval. In the second experiment, the effectiveness of exposure to the grid alone and to the light alone as well as to the combined light + grid cue was investigated after a 21-day training-to-test interval in the light condition, where light was related to safety and grid was associated with the shock, and in the dark condition, where both light and grid were related to the shock. The results indicate that whereas the compound light + grid cue was an ineffective retrieval cue in the light condition, it acted as an effective retrieval cue in the dark condition, supporting the hypothesis that coherence between retrieval cues is a necessary condition for effective cuing.