The Role of Adult Hippocampal Neurogenesis in Depression-Relevant Reward-Related Behaviours

The variability in the symptomatology of depressive disorders and antidepressant treatment response has led to an increased interest in the molecular, cellular, and circuit mechanisms of many aspects of affect. Evidence suggests a reduction in adult hippocampal neurogenesis (AHN) is associated with an increase in depression-like behaviour, though much of this evidence has been from studies using aversive tests (e.g., forced swim test). Here, I used touchscreen operant chambers, which allow for non-aversive and translational testing, to test the hypothesis that AHN plays a contributing role in emotion regulation. A panel of three touchscreen tests were chosen to assess different aspects of depression-relevant reward-related behaviour, namely probabilistic reversal learning, progressive ratio, and extinction learning. Results across these tests largely indicate that AHN knockdown does not affect sensitivity to feedback information, motivation across a variety of reward strengths, and the ability to cease responding after reward withdrawal. Therefore, it seems that a role of AHN in emotion regulation may only apply in stressful, but not non-aversive, conditions.