The problem of psychoanalysis is not the body of theory that Freud left behind, but the fact that it never became a medical science. It never tried to test its ideas.

You could double the number of synaptic connections in a very simple neurocircuit as a result of experience and learning. The reason for that was that long-term memory alters the expression of genes in nerve cells, which is the cause of the growth of new synaptic connections.

Long-term memory involves enduring changes that result from the growth of new synaptic connections.

Eric Kandel Quotes