Researchers swap in human brain cells for a mouse’s cortex

Researchers have transplanted lab‑grown human brain cells into the cortex of mice, producing animals whose brains are partly human. Reuters reports the transplant of human brain tissue into living mice, while Smithsonian Magazine and The Economist describe the resulting hybrids as mice with half‑human brains. The work was disclosed in several outlets on September 16, 2026.

The development promises a new platform for studying neurological disorders, a point highlighted by Smithsonian Magazine, which says the mice could revolutionize our understanding of such conditions. Neuroscience News adds that the lab‑grown tissue restored brain circuitry in the living animals, suggesting functional integration. Researchers and pharmaceutical developers stand to gain a more accurate model for testing therapies, while patients with disorders such as Alzheimer’s or Parkinson’s could eventually benefit from insights derived from these hybrids.

The experiment replaces only part of the mouse cortex, leaving the majority of the brain mouse‑derived, a nuance noted by eKathimerini.com and Science News, which refer to the animals as having partly human brains. Coverage does not detail long‑term behavioral outcomes or ethical review, leaving open questions about how fully human circuitry functions over time and what regulatory frameworks will apply.