Fig 2. Object location discrimination task.

A) The number of object exploration events decreased over the 5 habituation trials but doubled on trial 6 when object locations were changed (Mauchly’s test P = 0.3; effect of trial F_5,130 = 54, P<0.001, partial η² = 0.68; trial 6 vs trials 3,4,5 all P<0.001). There were no differences between sexes, genotypes and no interactions (all P>0.16). B) All groups showed above-chance discrimination indices, indicating increased object exploration on trial 6 relative to trial 5. Variance was not different across groups (Levene’s test F_3,26 = 1.9, P = 0.16). C) The number of rearing events decreased over the 5 habituation trials (Mauchly’s test P = 0.6; effect of trial F_5,130 = 11, P<0.001, partial η² = 0.30; trial 4&5 vs 1&2 all P<0.001) but did not change between trials 5 and 6 (P = 0.8). There were no genotype differences or interactions (all P>0.1) but females reared significantly more than males (F_1,26 = 14, P<0.01, partial η² = 0.35). D) The rearing discrimination index was above chance only in males and was greater in males than females (effect of sex F_1,26 = 4.5, P = 0.04, partial η² = 0.15). Due to unequal variance (Levene’s test P = 0.002) and a lack of sex x genotype interaction, genotypes were pooled and the sex difference was reanalyzed, confirming a greater rearing discrimination index in males and homogeneity of variance across groups (T₂₈ = 2.2, P = 0.03; Levene’s P = 0.25) E) Locomotion decreased over the 5 habituation trials in both sexes (Mauchly’s test P = 0.4; effect of trial, F_5,130 = 56, P<0.001, partial η² = 0.68) and increased from trial 5 to trial 6 following object displacement (P<0.001). Locomotion was greater in females than males, specifically on trials 4 and 5 (effect of sex, F_1,26 = 10, P<0.01, partial η² = 0.27; trial x sex interaction F_5,130 = 2.3, P<0.05, partial η² = 0.82; trials 4&5 different between males and females P<0.01). F) The locomotor discrimination index did not differ between genotypes (P = 0.6, partial η² = 0.01) or sexes (P = 0.07, partial η² = 0.12). Discrimination indices revealed above-chance levels of discrimination, except for female TK rats. Variance was not different across groups (Levene’s test F_3,26 = 0.7, P = 0.6). For all graphs: *P<0.05, **P<0.01, ***P<0.001. Graphs in panels A,C,E indicate mean ± standard error.