Charged particle irradiation results in altered spine density. Analysis of spine density in CA1 apical dendritic spines revealed significant changes in spine densities on apical dendrites from CA1 pyramidal neurons. (a) Representative dendritic images from all treatment groups. Scale bar = 2 mm. (b) Average total spine density, (c) thin spine density, (d) stubby spine density and (e) mushroom spine density. Inset images in c, d and e depict each spine type. Data represent means ± SEM. One-way ANOVA *p < 0.01, **p < 0.001, ****p < 0.0001