Figure 5.

A–C, Cumulative frequency distributions of spine volumes in PL neurons as a function of experimental treatment. Comparisons are made between yoked-saline and yoked-cocaine groups (A, C, E) and yoked-saline and self-administration cocaine (B, D, F). Each treatment results in a generalized rightward shift (i.e., increase) in spine volume regardless of cocaine treatment group, suggesting a mechanism leading to enlargement of spines relative to both forms of chronic cocaine administration. Rows show pairwise comparisons of distributions for the total (A, B), thin (C, D), and mushroom (E, F) spine population. K–S, Kolmogorov–Smirnov test.