With new optical techniques for
imaging single connections between neurons called synapses, we can see
constant turnover, with new synapses being formed and others disappearing.
This raises a puzzle.
In the face of so much turnover, how do memories stay stable over so many years?
This is a picture of one dendritic branch on a neuron which
receives inputs from other neurons.
The synapses are on the spiny knobs coming off the dendrite.
On the top, the dendrite was imaged before learning.
The same dendrite is shown below after learning and after sleep.
Multiple synapses that are newly formed
together on the same branch are indicated by the white arrowheads.
You are looking down into the brain of a live animal.
This is really a fantastic new technique.