One brain, different early paths

You do not have two brains. But regions of one brain may take different early paths before the organ has its familiar shape.

A Stanford-led team traced early neural cells in mouse embryos. One population contributed mainly to the forebrain and midbrain; another to the posterior hindbrain. Human stem cells grown in a dish showed related regional restrictions. That is a useful test, not a direct trace of a developing human embryo.

The study leaves open an earlier shared progenitor. The observation is about timing: regions of one brain may be on different paths before they look like parts of a brain.

We name organs by what they become. That can hide how they began.

Study by Rayyan T. Jokhai and Carolyn E. Dundes (co-first authors), Kyle M. Loh and colleagues. Nature Neuroscience (2026).