This looks interesting:
MRI Study Unfolds Clues to Memory
Those lacking structural fold in front of the brain were more likely to have faulty recollections
A common structural variation in the brain may explain why some people are better able to remember details of past events and to distinguish real events from those they were told about or may have imagined, scientists report.
I was blessed with a very good memory, including abilities like being able to read a book or see a movie and then give an accurate scene-by-scene description of it. I am only a moderately strong chess player but that may be because I didn't play seriously until I was an adult.
It would be intriguing to see if there is any correlation between this brain fold and, say, being a Grandmaster. I'd bet that GMs all have the fold, but that's just a guess. "Chess memory" seems to be somewhat correlated with good general memory in my experience, but correlation is not causation. People that really love chess and play a lot as youngsters usually can perfectly remember entire games a lot better than people like me. But I'm not convinced that they would be able to read a 20-page article on the Battle of Yorktown and summarize it more accurately a week later .
Anyway, I hope some brain researcher will take a look at this in relation to chess ability. It might be very interesting, especially if it turns out my speculation that strong players are more "folded" is wrong.