Heh, I read a book a lil while back, around Christmas methinks, and it said that memories were stored by a link of neurons in your brain. And the more links to that thought or thing in your brain(so the more neuron links) the easier it is to remember. (That's a very simplified version though, as I can't remember the details of it, I should really read that book again
)
And yes, all signals in the brain are electrical signals. (AFAIK)