Figure 4. Reduced dendritic spine density in the mPFC 15 weeks following exposure to cosmic radiation.

(a) Representative digital images of 3D reconstructed dendritic segments (green) containing spines (red) in unirradiated (top left panel) and irradiated (bottom panels) brains. Multiple comparisons show that total spine numbers (left bar chart) and spine density (right bar chart) are significantly reduced after exposure to 5 or 30 cGy of ¹⁶O or ⁴⁸Ti particles. Data are expressed as mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001 versus control; ANOVA. (b) Memory deficits correlate with reduced spine density in irradiated mice. Dendritic spine density (per 1.2 mm²) is plotted against the corresponding performance of each animal on the OiP task. Radiation-induced reductions in spine number correlate with reduced DI for novelty after exposure to ¹⁶O (5 cGy, P = 0.01; left panel) and ⁴⁸Ti (5 and 30 cGy, P = 0.01; right panel).