Meet a mouse whose brain cortex is made up of human cells

A team of neuroscientists at Stanford University, led by Sergiu Pașca, has successfully introduced human brain cells into the brains of genetically modified mice.

The researchers used human brain organoids—small, lab-grown clusters of neural tissue that mimic parts of the human brain.

These organoids were injected into mice whose brains were genetically altered to lack most of their cortex and hippocampus, two critical brain regions responsible for functions like memory and movement.

The human cells filled the empty space, growing to occupy nearly half of the mice’s brain volume within weeks.

This experiment demonstrates how human neural tissue can integrate and function within another species, raising new possibilities for studying brain development and diseases.