Role of the Hippocampus in Adaptation to Reward Loss: Emotionality or Cognitive Flexibility?



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Frustration is defined as an aversive emotional state triggered by reward loss. Despite compelling evidence associating reward loss with the etiology of anxiety and depression, neural correlates underlying adaptation to reward loss remain unidentified. Previous experiments conducted in our lab have demonstrated that hippocampal lesions impair the ability of rats to adjust to reward loss. However, it is unclear whether the impairment was due to a lack of emotionality (i.e. lesioned rats not feeling frustrated after reward loss) or a lack of cognitive flexibility (i.e. lesioned rats unable to modify previously learned responses). In order to investigate these questions, we exposed rats (with active and inactive hippocampi) to a reward-loss paradigm alongside a conditioned place preference (CPP) task designed to assess emotional responses. We found that while hippocampal-inactivated rats did not adapt their response to reward downshifts, they showed signs of negative emotion in the CPP task. This suggests that animals with a dysfunctional hippocampus do not lack emotionality but rather experience cognitive inflexibility. This research could contribute to revealing the function of neural circuits of reward loss, a critical step in developing treatments for anxiety, depression, and stress-related disorders.



Reward Loss, Hippocampus, Conditioned Place Preference, Drug Associated Memories, Behavioural Adaptation to Reward Loss, DREADDs