Experience changes the brain but must accommodate in some way to what has gone before. What happens during our development is that experiences, especially attachments, formed during that period change the brain in ways that affect emotions, relationships and health.
If early experiences involve the extremes of over stimulation or neglect, too much or too little arousal, then our ability to connect with others and our capacity for empathy can be diminished. In the case of overstimulation, the hair trigger of the brain—the amygdale—is fired repeatedly and the already established pathways to the right pre-frontal cortex can become super highways. It will take decades (around age 25) before we reach the threshold that will enable the left pre-frontal cortex to override earlier wiring. But we must still make a conscious effort to help this process along because the brain’s default is to stick with what it knows, and our subjective feeling that we are “at home” may in fact be out worst enemy.