Synaptic maintenance responsiveness of our model to intervals (three times repetitive stimuli, with various lengths of delay).

<p>The horizontal axis shows the intervals of each stimulation. The vertical axis shows the ratio of increase of synapses at two weeks after the first stimulation. The colored lines show the synaptic maintenance response with various <i>delays</i>. Red line: 0 min (no delay); Green line: 30 min; Blue line: 60 min; Purple line: 120 min. The two vertical dotted lines show the approximate upper limit and lower limit of intervals between three times stimuli for synaptic maintenance in experimental results <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051000#pone.0051000-Yamamoto1" target="_blank">[20]</a>.