Localized brain area for the control of impulsive behavior

The investigation has been carried out by a group of researchers in the Queen’s University in Kingston, (Ontario, Canada), leaded by the PhD Scott Hayton. The paper can be found here. They found an increased contribution of AMPA to NMDA receptors at excitatory synapses in the prefrontal cortex during the process of learning how to inhibit some "impulsive" behaviors.
As usual, by "localized" we don't mean that there is a "group of neurons", placed exactly "there", in every brain, which is responsible of that or that process...we know so far that the brain works "in concert", but there are some areas which are "specialized" in the elaboration of some kind of information, which occur usually in some areas and not in others. In particular, the ones in the frontal lobes are the most evolved cortices than humans developed with respect to other species, and scholars tend to describe them as the "centers" for the control and inhibition of "lower" level impulses, which should occur in internal structures in the brain and are associated with "instinctual" behaviors or reactions. They do this by suppressing in a top-down way the activity of the lower level circuits.

It looks extremely interesting to me how the more we study about these things, the more number of questions come to our mind related to the new findings. For example, the origin of these disfunctions is only genetic or it's also necessary a triggering event to unleash the chain reaction which affects the whole system??
And, moreover, which are the mechanisms which "cause" a bad functioning of this system for the control of the impulsive behavior that they found in the study?? They are supposed to be some pharmacological derangements...well, and when do they occur the first time? How are they promoted? From which other processes?
Are they triggered by some specific external behaviors/situations/events (bottom-up), influencing therefore also the top-down processes?? Or could be the "event" also internal, as for example, a specific set of thoughts (so, also top-down processes) which can influence the subsequent way of working of the system?

Click here to read the original article: Localizzata l’area cerebrale per il controllo del comportamento impulsivo (articolo in Italiano).