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the sliver that held

In 2025, a rare surgical case let researchers scan a split-brain patient whose corpus callosum wasn't fully severed — a surgeon stopped at roughly one intact centimeter of fiber, to protect a nearby artery. That patient's two hemispheres showed full, healthy synchrony, indistinguishable from someone with no surgery at all, while patients with a complete cut showed clear disconnection. It's a striking single case, not yet a general rule — and it doesn't settle the older, still-unresolved argument over whether split-brain patients ever really had two separate conscious minds to begin with. What it adds is one more entry in that debate: whether the unity you feel right now is a hard yes-or-no fact, or something built in degrees.