I think that this is talking about the brain. A certain portion of the brain (Area 39) which is part of a larger part of the brain (the parietal lobe) is where language (along with several other functions) is processed by the brain.
Not really. "Involved in" means to be a part of. "Many people were involved in this project". "Tom was involved in the process". "The pancreas is involved in sugar regulation". "Is processed by" means to be completely responsible for dealing with something. "The numbers are processed by the computer." "Tom will process your application." "Complaints are processed by our service department." So "involved with" is being a part of the process, but "processed by" means you handle the whole thing. Your sentence implies that Area 39 is one of the areas involves with language, but not the only one. I don't know if that is true or not.