"Current thinking about long-term memory in the cortex is focused on changes in the strengths of connections between neurons. But ongoing structural plasticity in the adult brain, including synapse formation/elimination and remodelling of axons and dendrites, suggests that memory could also depend on learning-induced changes in the cortical ‘wiring diagram’. Given that the cortex is sparsely connected, wiring plasticity could provide a substantial boost in storage capacity, although at a cost of more elaborate biological machinery and slower learning."
"The human brain consists of 10 to the 11th power neurons connected by 10 to the 15 power synapses. This awesome network has a remarkable capacity to translate experiences into vast numbers of memories, some of which can last an entire lifetime. These long-term memories survive surgical anaesthesia and epileptic episodes, and thus must involve modifications of neural circuits, most likely at synapses" (Chklovskii, Mel & K. Svoboda, "Cortical Rewiring and Information Storage," Nature, Vol. 431, 782-88).