Stanford neuroscientists led by Professor Sergiu Pasca have transplanted lab-grown human brain cells into the brains of mice, creating hybrids with partly human brain tissue. The work was published in Nature around September 16, 2026.

The mice could model conditions like autism, schizophrenia, epilepsy and cerebral palsy for drug testing and behavioral studies. Patient-derived organoids would let researchers watch genetic variants act in real time. Pasca noted that psychiatry has one of the lowest clinical-trial success rates in medicine, and even drugs that work in animal models fail dramatically in the clinic.

The scientists stress these are not mice that think like humans. The work was carried out with independent ethical scrutiny, though the New York Times and STAT noted calls for new ethical guidelines as the science advances.

Separately, the Connecticut startup Bexorg keeps donated human brains metabolically active for about 24 hours using a synthetic blood system called BrainEx, which Biohaven is using for drug testing, according to a Science report.