In chapter 21, CyFi explains some of his backstory to Lev. He brags that he used to have an IQ of 155, but he isn't quite as intelligent anymore. CyFi had been riding his bike when some "damfoo' in a Mercedes" hit him, inflicting serious injuries. CyFi says that he nearly died and that the accident had turned the right temporal lobe of his brain into "Jell-O."
CyFi's dads have enough money to pay off the doctors so that their son receives the best possible care. Most patients would have only gotten pieces of brain tissue to patch up the damage. Lev recalls that his sister, who suffers from epilepsy, has gotten hundreds of tiny brain pieces as treatment. Until this moment, he has never considered where those tiny brain pieces have come from.
Patching CyFi up wasn't good enough for his dads; CyFi compares this type of work to "puttin' spackle over a hole in a wall." So they paid off a surgeon so that he could receive an entire lobe from an Unwind. The Unwind's IQ wasn't as high as CyFi's original IQ, so he laments that he's now not quite as smart as he used to be—now only having an IQ of about 130.
This conversation demonstrates how their society has normalized the process of unwinding; people rarely even question the source of the transplants. It also demonstrates that there is underlying corruption that favors the wealthy over the poor.