Mice with human brain cells offer a tool to study disease. Ethicists ask: What’s next?

This side view of a lab mouse brain shows nerve fibers extending from the human graft (colored with green and red fluorescent proteins) through the mouse brain (colored with blue). Scale bar = 1 mm.

Neuroscientists have made a major advance in modeling the human brain in mice, offering a new way to study conditions like cerebral palsy. Ethicists ask if it changes how these mice should be treated.

(Image credit: S. Pașca lab)