There are two reasons he believes the neocortex could be replaced, albeit only slowly. The first is evidence from rare cases of benign brain tumors, like a man described in the medical literature who developed a growth the size of an orange. Yet because it grew very slowly, the man’s brain was able to adjust, shifting memories elsewhere, and his behavior and speech never seemed to change—even when the tumor was removed.

That’s proof, Hébert thinks, that replacing the neocortex little by little could be achieved “without losing the information encoded in it” such as a person’s self-identity.

The second source of hope, he says, is experiments showing that fetal-stage cells can survive, and even function, when transplanted into the brains of adults. For instance, medical tests underway are showing that young neurons can integrate into the brains of people who have epilepsy and stop their seizures.

“It was these two things together—the plastic nature of brains and the ability to add new tissue—that, to me, were like, ‘Ah, now there has got to be a way,’” says Hébert.

Very interesting. I’ve also seen research suggesting that the application of stem cells to damaged neural tissue within the spinal cord could repair it, so the idea that you could use a similar approach to actual brain health isn’t such a big leap. But still, wow. I wonder how long it would take for the immature cells to develop into “adult mode” that’s fully integrated into the patients cortex. In order to replace the entire brain, you’d have to do it in like, 8 parts, with years of recovery time in between each surgery. Also there would exist the potential for the new cells to develop into like, a second, smaller brain, if the connections sour or if the new material isn’t stimulated the “right” way.