(Image Courtesy of Yale University;cortical neuron is yellow at the top of the photo)
Previous research [1] suggested that after about the 7th week of development, the cells that will eventually make up most of the human cortex start to migrate from their point of origin, the ventricular zone.
Now, researchers at Yale and Oxford [2] have identified a type of cortical neuron that appears much earlier, as early as day 31 post conception. The neural tube has not even finished closing at this point. Here’s what we look like just a few days previously:
Another interesting aspect of these cells is that they are found at the outermost border of the developing brain (see the yellow cell in the first photo above). Normally, we describe the development of the cortex as happening in an “inside-out” manner. In other words, the first cells to leave the ventricular zone do not travel very far, and their journey may take hours. Subsequent cells must travel through these initial layers to the outside layers, in a journey that lasts weeks.
The ability of the developing brain to put all the cells in the right places and then connect them still leaves me with a feeling of awe. As we learn more about these new cells, other pieces of the developmental puzzle should fall into place.
- Chan, W.Y., Lorke, D.E., Tiu, S.C., & Yew, D.T. (2002). Proliferation and apoptosis in the developing human neocortex. Anatomical Record, 267, 261-276.
- Bystron, I., Rakic, P., Molnar, Z., & Blakemore, C. (2006). The first neurons of the human cerebral cortex. Nature Neuroscience, 9, 880-886.
