Behavioral assessment of mice after fractionated focal brain irradiation (3 × 2 Gy) followed by G-CSF treatment administered on days 1, 3, 5, 7, 14, and 21 after irradiation. (A) Contextual learning and fear conditioning assay. Time spent “freezing” as a percentage of total time (180 seconds) in shock-associated context A on days 1, 2, and 3 of training (left graph); percentage of time spent freezing on day 4 in context A (conditioned context) and context B (dissimilar context) in the absence of foot shock (right graph). *P < 0.05, 2-way ANOVA. n = 10–12 independent biological replicates. (B) Morris water maze assay. Mean time (in seconds) for each group to learn and to swim to the hidden platform over 5 successive trial stages (left) and mean time (in seconds) for each group to swim to a hidden platform at a new location over 3 successive trial stages (right). Asterisks indicate significant change relative to control. *P < 0.05, 2-way ANOVA. n = 10–12 independent biological replicates. (C) MRI segmentation analysis of mice 12–14 months after focal brain irradiation. Quantitative analysis of brain volumes obtained from automated segmentation. Box plots of white matter volume (including CC, external capsule, internal capsule, anterior commissure, and fimbria) indicate a reduction of white matter volume in the group exposed to radiation alone. Both the groups exposed to irradiation with G-CSF and the untreated (nonirradiated) control group have similar white matter volumes with higher median values compared with the radiation-only group. **P < 0.01; ***P < 0.001, Student’s t test. n = 5 independent biological replicates. Data are presented as mean ± SEM of biological replicates.