Fig. 2.

Properties of spine expansion in response to synaptic stimulation. (A) Expansion of a dendritic spine (red trace) in response to a 1-s, 100-Hz tetanus (arrow) is transient (note dashed circle highlighting spine area 60 min after tetanus) even though potentiation of the fEPSP (black trace) is persistent. (B) Representative trace of spine expansion (red) in response to repeated bouts of 1-s, 100-Hz tetanic stimulation (arrows) given 15–20 min apart. The same dendritic spine responds to each tetanus with a transient expansion despite the maintained increase in synaptic strength (black trace). (C) The mean (± SEM) percent of spines in the field of view that respond to a 1-s, 100-Hz tetanus is linearly dependent on the stimulus strength. (D) Scatter plot of spine area expansion in response to different numbers of stimuli at 100 Hz. White circles denote the mean expansion for each stimulation. A solid line marks 0% change, and a dashed line marks the 30% change required to detect an expansion above baseline noise. Each point is one spine.