Howard Hughes researchers report in today's Nature that they have found a third type of stem cell in the human brain, astrocytes. Until recently, astrocytes were thought to provide only a supportive, nurturing environment for the neuron, while this research shows that they can actually function as stem cells.

As Nadar Sadia, one of the primary researchers on the project details, "The astrocytes can form new stem cells and are able to generate all three types of mature brain cells...They form a novel ribbon-like structure in the brain's lateral ventricle. Stem cells from comparable areas in the rodent brain follow a distinct path from their place of origin to the olfactory bulb (a brain region that processes smells), where they create new neurons."

“This speaks to the plasticity of the human brain,” he said. “Certain cell types may have hidden potential.” These subtypes of astrocytes appear no different from any other astrocytes, implying that “it's possible that other astrocytes in other regions of the body have the same potential.”

Randall Parker's comment on this finding hits the nail on the head. "What seems surprising about this result is that only now in the year 2004 has anyone even checked to see if astrocytes can become nerve cells." Well, the research probably began several years ago, but the point is well taken.

As I discussed in "Yes, Your Brain is Very Complex" and Tom Ray detailed in his five part Brain Waves series on "Exploring the Brain's Boundaries", our understanding of the brain's complexity continues to grow. This is just another classic example.