Novel Object Recognition Test (NORT)

Four weeks after sham or BCAS operation, mice were tested for short-term recognition memory by NORT between 8 and 10 am, as previously described with slight modifications (Wang et al., 2004; Kleschevnikov et al., 2012; Ohtomo et al., 2020). Briefly, mice were placed in a clean empty cage for 10 min. Mice were then exposed to two identical objects in the same cage for 5 min (acquisition period). After an interval of 30 min, mice were then presented with two different objects (one original and one novel object, which were placed in the same position as the objects in the acquisition period) in the same cage for 5 min (retention period). Object recognition was videotaped and scored by the total investigation time either sniffing or touching the object. The performance of short-term recognition memory was described by the ratio of the time spent on the new object to the total time spent on both objects minus 0.5 (e.g., Discrimination index: ranged from −0.5 to 0.5). Experiments and analyses were conducted by an investigator who was blinded to the group allocation.