Actually no, these aren’t brains. This is a closeup of the fruit of a plant which is growing just off the bicycle path that I ride each week. These are about the size of a large grapefruit. I’m not sure what the real name of these things is. All the kids back in my home town called them monkey balls. Around here, they are commonly called hedge apples.

ADDED NOTE:
I found this article on Wikipedia: Maclura pomifera