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Brain metabolism after extended training in a fear conditioning task

Pavlovian fear conditioning (PFC) is one of the most used behavioural paradigms for studying the neurobiology of learning and memory. In this study, rats were trained in a conditioned suppression task receiving either three (limited training) or eight conditioning sessions (extended training). Rats in both training conditions came to suppress lever press behaviour as conditioning proceeded. After training, the neuronal metabolism of brain limbic regions was analysed using cytochrome oxidase histochemistry. A significant decrease in the metabolism of particular brain regions including the medial septum, anteroventral thalamus and medial mammillary nucleus, was observed only after extended training. However, no significant differences were detected after extended training in the basolateral amygdala, brain region traditionally involved in the formation and consolidation of aversive memories formed during PFC. Our results provide support for a differential involvement of the studied limbic regions on fear conditioning and anxiety.