Determining the contribution of neurogenesis to learning and memory by investigating the effects of depression and alcohol consumption on spatial pattern separation using high interference memory tasks

Abstract

Many young adult university students engage in frequent alcohol bingeing and have high depression scores, both of which are factors that can reduce hippocampal neurogenesis in rodents. Rodents with depleted neurogenesis exhibit selective deficits on high interference memory tasks including visual and spatial pattern separation. We predicted that young adult humans with high bingeing and depression scores would exhibit similarly impaired spatial pattern separation as a result of neurogenesis reductions. The relationships between alcohol bingeing, depression, and spatial pattern separation have, to this point, not been investigated in humans. We developed a novel computerized memory task for assessing spatial pattern separation in humans, loosely based on the “Concentration” memory card game. To further identify how sensitive this pattern separation function is to spatial separation between two stimuli, we developed the spatial separation recognition task (SSRT). We found that young adults with elevated depression and alcohol consumption scores exhibited impaired spatial pattern separation, in spite of intact performance on control tasks, consistent with a selective neurogenesis reduction. Further, this difference in performance seemed to be driven by performance at relatively larger separations.