(A) Representative Golgi images for postmortem human temporal lobe (left, 10×, stitched from nine separate image stacks), layer V pyramidal neurons with basal dendritic tree (top middle, 20×, pseudocolored in red; bottom middle, 40×, pseudocolored in green; scale bar, 50 μm). The right four panels (100×; scale bar, 5 μm) are representative images of proximal basal dendritic segments from two control subjects (C, aged 8 years and 18 years) and two ASD cases (A, aged 7 years and 15 years).

(B) Distribution of spine density (mean ± SD) in basal dendrites after the first bifurcation. Age and diagnosis are indicated for each sample. Controls aged 2–8 years [C(2–8 years)]: n = 5; controls aged 13–18 years [C(13–18 years)]: n = 5; ASD cases aged 2–8 years [A(2–8 years)]: n = 5; ASD cases aged 13–18 years [A(13–18 years)]: n = 5. Each point represents the average spine density for each individual neuron measured from each individual.

(C) A linear regression of spine density with age in the control subjects (n = 10) and ASD patients (n = 10). The number of spines per 10 μm was plotted against the age of each individual. Broken lines indicate 95% confidence intervals.

(D) Spine density (mean ± SD) for the controls and ASD patients in childhood and adolescence. Each point represents the mean spine density for an individual. Two-way ANOVA, Bonferroni post hoc test. ∗∗∗p < 0.001, ∗p < 0.05.

(E) The decrease of spine density with age was greater in the controls than the ASD patients (mean ± SD). ∗∗∗p < 0.001.