Stanford Creates Human–Mouse Chimera Whose Cerebral Cortex Is 92% Human Brain Tissue

Mad scientists are now growing living human brain tissue inside animals until it occupies nearly their entire cerebral cortex.

by Nicolas Hulscher, MPH

This is beyond disturbing...

Stanford University researchers have created a human–mouse chimera whose cerebral cortex contains 91.9% human brain tissue.

In a study published in Nature, scientists genetically engineered mice to develop without most of their cerebral cortex and hippocampus, leaving the animals with approximately 50% less total brain tissue than normal mice.

They then transplanted laboratory-grown human brain organoids into the vacant space. These organoids are three-dimensional clusters of living human brain cells grown from stem cells:

The transplanted human brain tissue expanded nearly fivefold between two and three months after transplantation, eventually accounting for 91.9% of the animals’ combined cortical tissue volume:

The human neurons did not simply remain isolated inside the mouse brain. They developed organized electrical activity, formed connections with the surrounding mouse nervous system, and extended nerve fibers all the way into the animals’ spinal cords.

Electrical activity within the transplanted human brain tissue was associated with the mice’s facial movements.

The animals underwent behavioral testing, including assessments of movement, coordination, and memory. Notably, mice containing human brain tissue performed above chance on a working-memory test, whereas mice missing most of their cerebral cortex without transplantation did not.

Mad scientists are now growing living human brain tissue inside animals until it makes up nearly their entire cerebral cortex.

Where does the madness end?

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Nicolas Hulscher, MPH

Epidemiologist and Foundation Administrator, McCullough Foundation

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