Critical contribution of young adult-born granule cells to spatial pattern separation

The dentate gyrus (DG) of the hippocampus is one of the few brain regions where new neurons continue to be generated throughout adulthood. Adult-born granule cells (ABGCs) have been implicated in pattern separation, the process by which similar experiences are transformed into distinct memory representations. However, the specific contribution of young ABGCs to spatial discrimination remains incompletely understood. Here, a modified spontaneous object location recognition task (SOLR) was used to investigate the role of young ABGCs in spatial pattern separation. Reversible silencing of young ABGCs during SOLR allowed us to assess spatial discrimination across configurations with different levels of similarity. Under low pattern-separation demand, animals preferentially explored the more distant object, whereas under high-demand conditions, exploration of the two objects was more similar. Remarkably, silencing a small cohort of young ABGCs produced a behavioral effect comparable to that observed following silencing of the entire DG. These findings suggest that a relatively small population of young ABGCs can exert a substantial influence on spatial discrimination when animals encounter similar spatial configurations. Together, these results support a critical role for young ABGCs in hippocampal pattern separation and highlight their contribution to spatial discrimination during a critical stage of neuronal maturation.