Researchers have created mice with half-human brains in an effort to understand and develop new treatments for disorders such as schizophrenia, epilepsy, cerebral palsy, intellectual disability and rare forms of dementia.

The scientists transplanted lab-grown human brain cells into animals that were engineered to be born without a cortex or hippocampus. This made space for the human tissue to grow inside the rodents’ skulls.

The procedure means scientists can now take cells from patients with brain disorders, turn them into brain tissue in the laboratory, and grow that tissue in living animals. The animals can then be studied to see how the disorder takes hold in human brain tissue, and how drugs might treat the conditions.