The role of the hippocampus in behavioural and endocrine responses to fear
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Recent evidence suggests that the hippocampus is functionally segregated along its longitudinal axis. The specific role of the dorsal hippocampus in spatial learning is strongly supported by both anatomical and behavioural data. The studies included in this thesis suggest that the ventral hippocampus also influences some, but not all, types of defensive fear-related behaviour. I have argued that the ventral hippocampus may not be involved in the processing of fear per se. The data suggest that the ventral hippocampus is not necessary for the performance of an escape response per se, but may rather have a role in bringing together sensory information from multiple sources and detecting potential mismatches between actual experience and memory for emotional aspects of a potentially threatening environment or situation. Such a comparator function may be a general feature of hippocampal processing, but ventrally located circuits may deal specifically with emotionally related inputs. It remains to be studied what aspects of the proposed roles of the dorsal and ventral hippocampus are mediated by the respective input areas originating in the entorhinal cortex and what is computed internally in the hippocampus. If the innate fear systems are organised in a modular manner, a major task for future research is to determine how the hippocampus interacts with other brain structures involved in behaviour during a potential threat.