SAN FRANCISCO, Dec 11: A new breed of supermouse is being developed in the laboratories of Stanford University.

But the aim of the project is not to create a rodent that thinks like a human but to devise a tiny model for the study of ailments such as stroke, schizophrenia, and Alzheimer’s and Parkinson’s disease, which are not easily studied in people.

However, the experiments have raised such deep ethical concerns that the project has been halted until an independent bioethics committee issues an opinion, which is expected early next year. The fear is that as research continues, animal brains might adopt human consciousness.

The experiments started last year when scientists injected stem cells from 10-week-old human fetuses into a mouse brain. Stem cells are the cells from which all others evolve.

Scientists found that after 14 months in the mice, the cells had thrived and spread to all parts of the mouse brain, where they resembled adult human cells characteristic of that region of the brain.

“Every part of the brain was populated with human cells,” said Dr. Irving Weissman, who heads the ethics committee.

The research indicated that stem cells could be used to repair damaged areas of the brain. But a mouse would never have human mental function, Weissman said, because a mouse brain lacks the size, complexity and organizational structure to engage in human thought.

But experts said that the same might not be true if human stem cells were injected into primates much more closely related to humans.

“If human cells can be implanted into mice, could they also be put in chimpanzees?” asked Larry Shapiro, a lawyer and bioethicist with the University of Southern California. “If you create a mentally augmented chimp, does it become a person? Can you keep it in a zoo? Can it apply for admission into law school?”—dpa