An early start on the road to reason

The cerebral cortex, a layer of cells just a few millimeters thick on the outermost surface of the brain, is largely what makes humans “noble in reason and infinite in faculties.” New Yale research shows that developing embryos generate the first neurons of the cortex only 31 days after fertilization—much earlier than previously thought.

Using precise cellular markers, Pasko Rakic, M.D., Ph.D., chair and Dorys McConnell Duberg Professor of Neurobiology, and colleagues at the University of Oxford discovered “predecessor” neurons in human embryos before the neural tube, the precursor of the central nervous system, had completely closed. These precocious cells produce long extensions that may pull them to different locations as the brain develops while also acting as temporary scaffolds to guide late-blooming cortical neurons to their proper locations.

In the July issue of Nature Neuroscience, the researchers say that studying how predecessor cells help to generate and wire up the 20 billion neurons of the adult human cortex may give us new insights into how we differ from our primate ancestors and shed light on the causes of mental illness.