Forming memories doesn’t require new synapses (let alone new branches or neurons); it requires the strengthening of preexisting synapses.1 What does “strengthening” mean? In circuitry terms, if neuron A synapses onto neuron B, it means that an action potential in neuron A more readily triggers one in neuron B. They are more tightly coupled; they “remember.” Translated into cellular terms, “strengthening” means that the wave of excitation in a dendritic spine spreads farther, getting closer to the distant axon hillock.
