Figure 4

Factors that may affect the fate of dendritic spines.

(a) Dependency on pre-existing density of the dendritic segments. Spine number increments depended on pre-existing density after 3× cLTP. However, there was no correlation between spine number reduction and pre-existing spine density. Changes of 0 to 60% indicate increases and changes of 0 to −60% indicate decreases. Regression lines were drawn, although they were statistically insignificant. R (regression) and F (variance) values are R = 0.355, F = 0.125 for the 3× mock group and R = 0.173, F = 0.431 for the 3× cLTD group. (b and c) Dependency on the spine shapes. The spines are classified into 3 types. Representative images are shown in (c). In this examination, the cultures were fixed and the cells were injected with a fluorescent dye. Thus, comparisons are made between spine type distributions of 3× mock and 3× cLTD groups as shown in (d). Note the reduction in mushroom type spines. In (d), the dendritic segments examined are 28 and 26 from 9 and 10 independent cultures for the 3× mock and 3× cLTD groups, respectively. Significance values are P = 5.3 × 10⁻³, t(52) = 2.9 for **1 and P = 0.027, t(46) = 2.3 for *2 in paired t-test.