Higher depression scores are associated with lower pattern separation performance in humans

Abstract: Memory impairment has been connected to depression, however this association appears complex. Pattern separation is a specific hippocampal function, which separates similar events and stimuli into distinct memory representations. Hippocampal volume reduction has been seen in individuals suffering from depression. Multiple rodent studies have shown that adult neurogenesis in the dentate gyrus of the hippocampus is crucial for proper pattern separation. There are several factors that are thought to influence neurogenesis. For example stress, depressive symptoms and aging have a negative effect on neuronal plasticity. On the other hand, exercise and antidepressants seem to accelerate neurogenesis. Patients with hippocampal damage are impaired in the pattern separation tasks, but not in the recognition memory tasks. Few studies have investigated the direct relationship between depression and pattern separation in humans. The current study addressed this issue by testing Swedish University students. We found a negative correlation between depression scores and pattern separation performance. The correlation between depression scores and recognition memory was not significant. Thus, we argue that depression is linked to impaired pattern separation ability. Unexpectedly, a gender-difference in pattern separation in favor of female subjects was found. We suggest that this issue should be investigated further by future studies.