In the first probe trial (removal of the box 48 h after the last training session), the time spent in the target quadrant, a parameter not affected by hypolocomotion or anxiety, was significantly shortened in EE-housed NPY KO mice (36.4 ± 10.6 s vs. 75.8 ± 11.2 s), indicating a memory deficit (Fig. 3e, Supplementary Movie S2). The gene discussed is NPY; the disease is Anxiety.