FIGURE 14-20 Effects of Experience on Dendrites (A) Three inputs to a pyramidal cell dendrite. Each axon forms a synapse with a different dendritic spine. (B) In forming multiple spine heads, either the original axons can divide and innervate two spine heads or new axons or axon collaterals (dotted outlines) can innervate the new spine heads. (C) Single dendritic spines may sprout multiple synapses.