After development, reelin is secreted in the cortex and hippocampus by gamma-aminobutyric acid-ergic interneurons. Through binding of ApoER2 in the hippocampus, it plays a role in the NMDA receptor activation that is required for long-term potentiation, a mechanism by which two neurons gain a stronger, longer-lasting transmission due to simultaneous firing. The increased synaptic plasticity associated with this process is essential in development of memory and spatial learning. Studies with mice have shown less expression of ApoER2 leads to impaired spatial learning, fear conditioned learning, and a mild disruption to the hippocampus.