I grew up watching TV shows where characters got whacked over the head fairly routinely, woke up, and was normal again. Not even a look at by a doctor. And then, a few years ago, I met a former soldier who had a service dog. She had a serious concussion and one of the aftereffects was that she lost her depth perception. If there was a hole in the ground, she could not tell it was there!
The Washington Post published this article on writer Ernest Hemingway. He killed himself in 1961, well before we started to learn from war what effects concussions do to the human brain.