Elon talked about this 10 years ago, saying we currently have 2 layers and how Neuralink could be the third: “When Elon refers to a “digital tertiary layer,” he’s considering our existing brain having two layers—our animal limbic system (which could be called our primary layer) and our advanced cortex (which could be called our secondary layer). The wizard hat interface, then, would be our tertiary layer—a new physical brain part to complement the other two.” Link: https://waitbutwhy.com/2017/04/neuralink.html

The idea of the brain having a primitive layer and more refined layers is much more than ten years old [0]. The new finding here is that distinct layers have different progenitor cells.

[0] https://en.wikipedia.org/wiki/Triune_brain