Fig. 1.

Age-dependent motility in GFP-containing neurons.A, P1 cell grown in culture for 6 d expresses considerable spine motility. Two images on the left are successive, taken 5 sec apart, showing several dendrites, and spines in focus on one of them. On the right is a subtracted image, showing in black and white a disparity between the two left images, withgray showing the same position of the dendrite in the two images. Note that most of the spines stain black orwhite and that the parent dendrite is primarilygray. B, GFP-containing cell, grown for 2 weeks in culture, same series of images as in A. Much less motility is detected in the subtraction image on theright. C, Same conditions, 30-d-old culture, showing mature dendritic spines, expressing little or no distinct motility. Below, computer-generated contour frames taken from successive images of the spine shown in C witharrow, to illustrate little or no lateral motility of the spine. Scale bars: A–C, 3 μm; C, bottom, 1 μm.