Scientists create mice with brains that are nearly half human

Stanford scientists used genetic engineering to remove mice cortex and implant human neurons, which multiplied from a few hundred to millions and connected to the rodents' brains. The mice showed human traits: brain damage under oxygen shortage and von Economo neurons that die in frontotemporal dementia.

• Human neurons grew from a few hundred to several million
• By volume, nearly half of the mice brains became human
• Mice developed von Economo neurons linked to dementia
• Experiment stopped at six months due to ethical questions