Subject: 1.) Explain PET...please. 2.) What happens to the brain at/around puberty?

I understand that a PET study begins by sending a positron emitting fluid in the blood stream and it then examines gamma ray production as the positrons and electrons wage war on one another, and I understand that this gamma producing warfare is evaluated in some way to determine which areas of the brain are active during any given activity. However, I do not understand how reliable/valid this technique is for isolating complicated actions such as language production, reception, processing, etc. As I understand the issue, the brain has several areas which are active in varying degrees at any given time depending on the kind of linguistic demands it undergoes for any given task. Are there any PET-based studies on language specific questions? I'm also curious to know about what linguists often refer to as "the critical stage" in language acquisition. It is generally accepted that around puberty, language acquisition takes a substantially different cognitive role: before puberty, an LAD (language acquisition device) is hypothesized to be active as a kind of innate neurological system (kinda like radar in bats), but after puberty, this LAD stops and language acquisition becomes a matter of the neocortex's ability to solve problems, much in the way it solves other computational matters. Is there a critical period for other brain related functions? If so, does the cerebellum play a role in this critical period? As these questions are of extremely great importance to the future of neuroscience, I would like to submit them to Mr. Joe Simpson, Esq., (soon to be Mr. Joe Simpson, M.D., Ph.D., Esq.) whom I believe to be one of this century's greatest neuro-type-guys. If Joe can't answer these questions, then they probably can't be answered.

Re: 1.) Explain PET...please. 2.) What happens to the brain at/around puberty?