Adolescent male Fmr1 KO and WT mice were treated with lithium for 4 weeks and then following testing, lithium treatment was discontinued for 4 weeks and the mice were retested. Prior cognitive testing in the same paradigms had no effect on re-test performance in untreated WT mice or Fmr1 KO mice (Student's t-test, p>0.05 compared to retest; coordinate spatial processing task: WT no treatment: n=7, t(12)=0.32, p>0.05; FX no treatment: n=9, t(16)=0.27, p>0.05; categorical spatial processing task: WT no treatment: n=7, t(12)=0.24, p>0.05; FX no treatment: n=9, t(16)=0.28, p>0.05). (A) Exploration ratio in the coordinate spatial processing task. (one-way ANOVA followed by post hoc Bonferroni's multiple comparison test; F(3,29)=11.34, p<0.05). (B) Exploration ratio in the categorical spatial processing task. (one-way ANOVA followed by post hoc Bonferroni's multiple comparison test; F(3,27)=17.29, p<0.05). *p<0.05 compared to matched WT mice. n=7 WT no treatment; n=7 discontinued lithium treatment; n=9 Fmr1 KO no treatment; n=9 Fmr1 KO discontinued lithium treatment.