GRIN2B and Cognitive impairment: (1) Investigate effects of EE on cognitive impairment, levels of BDNF and NMDA receptor subunit 1 (NR1) and subunit 2B (NR2B) in hippocampus; (2) EE exposure improved spatial cognitive performance and non-spatial memory performance. EE increased levels of BDNF and NR1 protein in hippocampus.