sst2, sst4, and sst2/sst4 double knock-outs show normal ORM. A, When tested with a 5 min retention interval, sst2 and sst4 knock-out mice are equal to wild-type mice in the ability to detect a novel object. B, sst2, sst4, and sst2/sst4 knock-out mice show normal ability to discriminate a novel object after a 1 h retention interval. *Significant preference index (one-sample t test).