Scientists grow mice with half-human brains to study neurological disorders

Scientists at Stanford University have created mice with brains containing millions of functioning human neurons, a development that could enable new research into human brain function and neurological disorders. The researchers genetically engineered mice lacking a key brain region, the cerebral cortex, then implanted human neurons that multiplied from hundreds to millions and connected with the mouse brain. The mice behaved normally despite nearly half their brains being human-derived. The study, published in Nature, may help research conditions like frontotemporal dementia and oxygen-deprivation brain damage in newborns. However, the work raises ethical questions about consciousness, with researchers halting experiments before further neural connections could form.