I get the part about popping into existence but how would even so much as a bilipid layer around a single cell form, let alone a whole brain? Where are all the antiparticles in this, except shooting around? Even if all the particles pop into existence perfectly placed for a single quanta of Plank time, aren’t the antiparticles destructively interfering with all the other particles even before they begin to annihilate? I imagine they would prevent any chemical reaction happening at all at that density. What about all the force carriers? Can they even pop into existence in the quantum foam coupled?

It wouldn’t really resemble a brain in biological sense of the world because the only stimuli it can and will react to is its own disintegration. It’s hard to justify it even “existing” at all. A “virtual” brain in the sense of virtual particles perhaps, except it seems quantitatively useless.