What is it outside of the cells that causes the intracellular recordings to vary?
I put together a brief summary of neocortex cell types and circuits for you and have attached it as a .doc file. I think you will find it useful in following this problem through. I am not sure how much of what is in it that you already know, so hopefully it will be a constructive resource for you.
It is a pretty elegant system, and, as you may already know, the neocortex is highly developed and has fully evolved only in the most intelligent animals. Although the feedback concept is found in many animals and physiological systems, the neocortex puts an interesting little twist in it.
The closest feedback mechanisms and loops that you might think of involve biochemicals and hormones, ie. positive feedbacks- when we are young and begin to grow, this type will help to stimulate the growth to continue and will stimulate different systems to grow in response, like when your skeleton grows, your skeletal muscles must also grow with ...