Brains
Gray Matter
noun
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.
自分の体のどこかを変えられるとしたら、ぜっ対に脳みそを変えるね。
If I could change anything about my body, it would definitely be my brains.
今日はつかれすぎて脳みそが全然働いていません。
I'm so tired today, my brains just aren't working.
「ドタマかち割って脳みそストローでチューチュー吸うたろか！」とお化けは怒って言った。
"Do you want me to crack your skull open and suck out your brains with a straw?" the ghost said angrily.