I feel like it's gotta be very different.
The reason I pondered this was because while in China I am pretty fluent in understanding what is being said, but I have a very hard time speaking. I like to think that my accent is pretty good, it's just that a lot of the time I can't think of the words I need to be speaking. But when I hear them, I immediately know that's what I meant.
Similarly, in English I sometimes find myself stumbling as I write or speak when I feel like there's a perfect word for something I'm trying to express but I just can't think of it... I'm not a vocab buff, I don't read books often, and I don't read articles beyond the fold. So there's a reason why I might not have as many words right on the tip of my tongue. But again with these situations, it's similar to my situation in China where I know what I'm trying to say, and I'm pretty sure that I know the word, I just can't say it!
So that got me thinking about how connected those parts of the brain are. Knowing a new second language, and knowing your own language pretty well. I guess it seems pretty obvious that they are exactly the same? But I'm unsure.
Also I sort of feel that the language understanding part of the brain is much different than the language speaking/writing part of the brain. As shown by my lack of ability to proactively use big English words and use many words at all in Chinese when I can understand both perfectly well.
This research article suggests that they are the same part of the brain, but it makes no sense to me.
I'm very interested in how the brain works, how memory is stored and retrieved, etc so someone please enlighten me!