https://slatestarcodex.com/2020/06/11/wordy-wernickes/

 

There are two major brain areas involved in language. To oversimplify, Wernicke’s area in the superior temporal gyrus handles meaning; Broca’s area in the inferior frontal gyrus handles structure and flow.

If a stroke or other brain injury damages Broca’s area but leaves Wernicke’s area intact, you get language which is meaningful, but not very structured or fluid. You sound like a caveman: “Want food!”

If it damages Wernicke’s area but leaves Broca’s area intact, you get speech which has normal structure and flow, but is meaningless. I’d read about this pattern in books, but I still wasn’t prepared the first time I saw a video of a Wernicke’s aphasia patient (source):