If I could change anything about my body, it would definitely be my brains.
I'm so tired today, my brains just aren't working.
"Do you want me to crack your skull open and suck out your brains with a straw?" the ghost said angrily.
Do you know みそ Soup and how miso goes in it? This is that miso. It's soft and strange feeling. Now, your brain miso, that's your brains or your gray matter. Essentially, if someone cuts your head open with a katana, this is perhaps what would come out.
Reading is just what you learned with the kanji. Just use your 脳 a bit and it should be easy.