The history of understanding brain disorders that lead to language difficulties can be found here:
and a more detailed version of the history of brain study related to language can be found here:
The symptoms of brain damage, recognizable by language difficulties, is simplified here:
What does this mean to us language learners? We have to study and practice using all of our coordinated areas of the brain, used in language, including physically writing down words that we learn, listening and repeating over and over, as well as reading.
As this article states:
It turns out that the language you speak does change the way your brain processes language, studies have shown.
We are rewiring out brains, not just learning some new words, when we attempt to gain fluency in other languages, so be persistent and patient.
Research has demonstrated numerous advantages to learning a new language beyond mere communication. People who are bilingual are better able to carry on two tasks at once, switching back and forth between activities more seamlessly and weeding out irrelevant information better. But here’s the downside: Languages can actually compete in your mind, and you may start forgetting some vocabulary of the language you use less.
Which may explain why I have to be careful how much Spanish I learn as I try to solidify my French. As for English, I mainly grunt and point now anyway, so no danger there.