Scientists Grow Mice With Half-Human Brains to Crack Neurological Disorders

(MENAFN) Researchers have engineered mice with brains that are roughly half human, a breakthrough aimed at unlocking new treatments for conditions such as schizophrenia, epilepsy, cerebral palsy, intellectual disability and rare dementias, according to findings reported by media on Thursday.

The team implanted lab-cultivated human brain cells into mice that had been genetically altered to be born without a cerebral cortex or hippocampus—deliberately leaving room for the human tissue to take hold. The method lets scientists harvest cells directly from patients, convert them into brain tissue in a lab setting, and observe firsthand how disorders disrupt human neurons, as well as how potential therapies might counteract them.

"We've been trying really hard as a community to find therapeutic solutions for these conditions, but the reality is that in psychiatry and neurology we've been left behind," said Sergiu Pasca, the Stanford University professor who spearheaded the study.

He pointed to a fundamental barrier that has long stalled progress in the field. "The human brain is very complex, but it's also because the human brain is inaccessible," he added. "Our goal has been to make aspects of human brain development and function accessible for investigation."

The project expands on earlier work involving neural organoids—clusters of lab-grown human brain cells that replicate certain structural features of an actual brain. Though organoids hold promise for medical research, they've also stirred ethical debate over questions of consciousness, pain perception and animal welfare.

Pasca noted that the research passed through rigorous ethical review before proceeding. Emily Jackson, a law professor at the London School of Economics, weighed in on the broader stakes: "Animal welfare is a really important concern," she said, adding that the mice would require careful, ongoing monitoring.

Detailing the methodology in the journal Nature, Pasca wrote that newborn mice were injected with approximately 100,000 human brain cells apiece. The animals were missing about 14 million mouse brain cells, and in their place grew roughly 4 million human ones—accounting for close to half of their total brain volume.

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