I have this personal theory that all memory and thoughts throughout the brain are linked. Our consciousness is in a constant flow through passages of memory and experience. Think of it as a river with many branches in every direction. Each branch is a link from one memory, thought or concept to another. For now don't worry about upstream or downstream. Maybe think instead that you are the river and your consciousness is the single point in the mind that moves to the others.

Eventually we find ourselves in this a place in the river of the mind where we can see a destination we would like to reach but it isn't branched to directly (maybe the branch has dried up). This is where we must travel to other branches related to the subject to see if we can make it back.

"It's not that I can't remember your name it's just that I have lost the way to it"