Quick! Name a small and numerous component in the brain that allows us to think.
If you said “neuron,” you would be only partially correct. According to Carl Zimmer’s blog at Discover, “The Loom,” evidence is accumulating that thinking is also accomplished by astrocytes
—named for their starlike rays, which reach out in all directions—are the most abundant of all glial cells and therefore the most abundant of all the cells in the brain. They are also the most mysterious. A single astrocyte can wrap its rays around more than a million synapses. Astrocytes also fuse to each other, building channels through which molecules can shuttle from cell to cell.
To put glia into a broader perspective, consider Zimmer’s introduction to his post on glia:
I’ve asked around for a good estimate of how many neurons are in the human brain. Ten billion–100 billion–something like that, is the typical answer I get. But there are actually a trillion other cells in the brain. They’re known as glia, which is Latin for glue–which gives you an idea of how little scientists have thought of them.
It has now been shown that astrocytes can sense incoming signals, respond with calcium waves, and produce outputs
In other words, they have at least some of the requirements for processing information the way neurons do. Alfonso Araque, a neuroscientist at the Cajal Institute in Spain . . . find that two different stimulus signals can produce two different patterns of calcium waves (that is, two different responses) in an astrocyte. When they gave astrocytes both signals at once, the waves they produced in the cells was not just the sum of the two patterns. Instead, the astrocytes produced an entirely new pattern in response. That’s what neurons—and computers, for that matter—do. If astrocytes really do process information, that would be a major addition to the brain’s computing power . . . neuroscientist Andrew Koob suggests that conversations among astrocytes may be responsible for “our creative and imaginative existence as human beings.”
