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Activity cage measurements of horizontal (Upper) and vertical (Lower) activity in male mice at different ages. Mutant animals lacking brain AM (gray bars) are more active than their wild-type littermates (open bars) during the first 6 months of life. Bars represent the mean ± standard deviation of 10 mice. The whole experiment was repeated twice, and a representative example is presented here. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ns, no significant differences.
