The present study sought to determine whether post-training exposure to a novel or familiar object, encountered in either the location of the original fear conditioning (black compartment of a passive avoidance {PA} chamber) or in a neutral setting (open field where initial object training had occurred) would prove capable of reducing fear at subsequent test in a passive avoidance task. In Experiment 1, Long-Evans rats that encountered a novel object in either the black PA compartment or the open field, as well as those encountering a familiar object located in the black PA compartment all displayed weaker fear at test than did those subjects that encountered a familiar object in the open field. These effects were explained in terms of a counter-conditioning of fear resulting from the appetitive aspects of novelty exposure. Experiment 2 compared the fear-reducing capabilities of novel object exposure to a more simple extinction procedure. While both the extinction and novelty groups generally showed reduced fear compared to control animals, some evidence suggested that novel object exposure resulted in significantly less fear at test than did extinction alone.

Open Access