"The sleeping brain processes memories of real-time events up to 6 or 7 times faster than the waking brain.
All of our memories are broken down according to types of information into modules stored in the brain's cortex and then networked through the hippocampus. The modules are then retrieved by "tags" assigned by the hippocampus and reconstructed to form our memories of the event. It happens this way because not every neuron can connect to every other neurons.
“The initial creation of the tag is made through existing connections," said McNaughton. "In order to do the rewiring necessary to have the intermodular connections carry the burden takes time. What you have to do is reinstate those memories multiple times. Every time you reinstate the memory, the modules make a little shift in the connection . . . something grows this way, grows that way, a connection gets made here, gets broken there. And eventually, after you do this multiple times, then an optimal set of connections gets constructed.” science, 16.11.07