The numbers of spines that were eliminated or newly generated were counted in dendritic regions over 4–7 d. They are expressed as a percentage of the spine number on the preceding day. Data are means ± SEM for the number of dendritic regions indicated. Spine density tended to decrease or increase in the absence or presence of NMDAR inhibitors, respectively, consistent with the general trend for spine elimination during development and its blockade by NMDAR inhibitors (Zuo et al., 2005a). *p < 0.001; ^†p = 0.85 (not significant), versus corresponding value for the control condition (unpaired Student's t test).