Neuroscientists have long speculated that information storage would likely be more permanent if changes in synaptic strength were accompanied by some sort of morphological alteration in the brain, in particular among the tiny dendritic protrusions known as spines.1 These specialized structures on the neuron's postsynaptic end are 1 to 2 µm long, and tens of thousands of spines can coat a single neuron, making "the whole dendrite look spiny, like a rose," says Bonhoeffer.
The curious thing about spines isn't simply their large number, rather the observation that "the vast majority of synapses sit on the head of a spine," says Bonhoeffer. In fact, the spine-synapse relationship is nearly one to one, he notes, which partially explains why scientists believe that the spines have something to do with memory: the more spines, the more synapses, and therefore, goes the theory, a better memory.
But scientists have had a difficult time ...
