Newborn Neurons Separates Similar Memories

Adult-born granule cells (abGCs) have been implicated in memory discrimination through a neural computationknown as pattern separation. Here, using in vivo Ca2+ imaging, we examined how chronic ablation oracute chemogenetic silencing of abGCs affects the activity of mature granule cells (mGCs). In both cases,we observed altered remapping of mGCs. Rather than broadly modulating the activity of all mGCs, abGCspromote the remapping of place cells’ firing fields while increasing rate remapping of mGCs that representsensory cues. In turn, these remapping deficits are associated with behavioral impairments in animals’ abilityto correctly identify new goal locations. Thus, abGCs facilitate pattern separation through the formation ofnon-overlapping representations for identical sensory cues encountered in different locations. In theabsence of abGCs, the dentate gyrus shifts to a state that is dominated by cue information, a situationthat is consistent with the overgeneralization often observed in anxiety or age-related disorders.