Almost all neuroscientists believe that memories are stored in the connections between neurons: synapses. Learning, then, consists of the strengthening of some synapses, the weakening of others, and maybe even the formation of entirely new ones. But a paper from Catherine Miller and colleagues suggests that changes to DNA are also involved: Cortical DNA methylation maintains remote memory.
DNA is a series of bases, and fundamentally there are just four: C, A, T and G. However, the Cs and the As can be
i.e. modified by the addition of a very simple methyl chemical group. They then stay that way until they get demethylated in the reverse process. Methylating a gene generally reduces its expression.
It's a bit like writing notes in pencil on top of a printed document: it doesn't change the underlying genetic sequence, but it's a semi-permanent change and it can be inherited by dividing cells. ...
