Effect of a G-CSF deficit on recognition memory. The short-term retention test was performed 1 h after training (A) and a long-term retention test 24 h after training (B). The recognition index calculated for each animal was expressed by the ratio T_NO/(T_FO + T_NO) [T_FO = time spent exploring the familiar object; T_NO = time spent exploring the novel object]. Significant changes between training and test condition are indicated by asterisks (*p < 0.05; **p < 0.01; ***p < 0.001), significant differences between G-CSF^−/− and wild-type mice are indicated by horizontal bars (p < 0.05).