Monosynaptic inputs to new neurons in the dentate gyrus

• Published in: Nature communications Vol. 3; no. 1; p. 1107
• Main Authors: Vivar, Carmen, Potter, Michelle C., Choi, Jiwon, Lee, Ji-young, Stringer, Thomas P., Callaway, Edward M., Gage, Fred H., Suh, Hoonkyo, van Praag, Henriette
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 2012; Nature Publishing Group
• Subjects: 631/378/1697; 631/378/2591; 631/378/368; Animals; Dentate Gyrus - cytology; Electrophysiology; Humanities and Social Sciences; Immunohistochemistry; Male; Mice; multidisciplinary; Neurons - metabolism; Neurons - physiology; Neurons, Afferent - physiology; Science; Science (multidisciplinary); Synaptic Transmission - physiology
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms2101

Adult hippocampal neurogenesis is considered important for cognition. The integration of newborn dentate gyrus granule cells into the existing network is regulated by afferent neuronal activity of unspecified origin. Here we combine rabies virus-mediated retrograde tracing with retroviral labelling of new granule cells (21, 30, 60, 90 days after injection) to selectively identify and quantify their monosynaptic inputs in vivo . Our results show that newborn granule cells receive afferents from intra-hippocampal cells (interneurons, mossy cells, area CA3 and transiently, mature granule cells) and septal cholinergic cells. Input from distal cortex (perirhinal (PRH) and lateral entorhinal cortex (LEC)) is sparse 21 days after injection and increases over time. Patch-clamp recordings support innervation by the LEC rather than from the medial entorhinal cortex. Mice with excitotoxic PRH/LEC lesions exhibit deficits in pattern separation but not in water maze learning. Thus, PRH/LEC input is an important functional component of new dentate gyrus neuron circuitry. Adult neurogenesis in the mammalian brain is implicated in the storage and processing of memories. Vivar et al. label afferents to new dentate gyrus granule cells and find that they receive direct input from the perirhinal and lateral entorhinal cortex and that these inputs enable spatial pattern separation.