The Other Brain

By Neuroskeptic | February 28, 2011 9:18 pm

An interesting new book from R. Douglas Fields: The Other Brain.

Glia” is a catch-all term for every cell in the nervous system that’s not a neuron. We have lots and lots of them: on some estimates, 85% of the cells in the brain are glia. But to most neuroscientists at the moment, they’re about as interesting as dirt is to archaeologists. They’re the boring stuff that gets in the way. The name is Greek for “glue”, which says a lot.

It’s telling that most neuroscientists (myself included I confess) use the term “brain cells” to mean neurons, even though they’re a minority. Hence the book’s title: Douglas Fields argues that glia constitute a whole world, another brain – although of course, it’s not seperate from the neuronal brain, and neuron-glia interactions are the really interesting thing and the central theme of the book.

Glia have historically been regarded as mere “housekeepers”, keeping the brain neat and tidy by cleaning up the byproducts of neural activity. Douglas Fields explains that there’s actually a lot more to glia than that, but that even if they were just housekeepers, the housekeeping they do is extremely important.

Astrocytes, one kind of glial cell, are key to the regulation of glutamate levels in the brain. Glutamate is by far the most common neurotransmitter yet it’s also the most dangerous: glutamate can kill neurons if they receive too much of it (excitotoxicity). I previously wrote about some bad clams which can cause permanent brain damage if who eat them; the toxin responsible mimics the action of glutamate.

By quickly clearing up glutamate as it’s released from neurons, astrocytes perform a vital function which saves the brain from self-destruction. Yet recent evidence has shown that they don’t just mop up neurotransmitters, they also respond to them, and even release them. People are nowadays talking about the “tripartite synapse” – presynaptic neuron, postsynaptic neuron, and glia.


Glia even have their own communication network quite seperate from the neuronal one. Whereas neurons use electrical currents to convey signals, and chemicals to talk to other cells, astrocytes are interconnected via direct gap-junctions – literally, little holes bridging the membranes between neighbors.

Waves of calcium can travel through these junctions across long distances. The function of this glial network is almost entirely mysterious at present, but it’s surely important, or it wouldn’t have evolved. (A few types of human neurons do the same thing; in some animals it’s more common.)

The subtitle is overblown, as subtitles often are (“From Dementia to Schizophrenia, How New Discoveries About the Brain are Revolutionizing Medicine and Science“); the book also repeats itself in a number of places, especially when it’s castigating neuroscientists for overlooking glia for so long (a fair point, but it gets old.) Overall though it’s very readable and it’s got some nice anecdotes as well as the science.

The Other Brain makes an excellent case that neuroscience can’t remain neuron-science if it hopes to answer the big questions. It’s certainly opened my eyes to the importance of glia and given me ideas for my own research. As such it’s one of those rare popular science books that will prove interesting to professionals and others too.

Link: Also reviewed here.

Disclaimer: I got a free review copy.

CATEGORIZED UNDER: books, science
  • http://www.blogger.com/profile/14539175222290571773 Dick

    Cool! Sounds up my alley. I'm interested in the role of glial cells, but really don't know much about them at all. Plus I'm in computational neuroscience so glia are almost always overlooked.

    However, there was a computational study in the Journal of Neuroscience last year that took into account the role of potassium ion clearance in network behaviour, with some rather interesting results (the same network could exhibit normal or 'pathological' epileptic-type behaviour depending on the extracellular potassium concentration/clearing dynamics): http://www.jneurosci.org/content/30/32/10734.abstract

  • Anonymous

    Thanks for the heads up on the book! At last glial cells (or at least astrocytes) are beginning to get the recognition they deserve!

  • http://www.blogger.com/profile/06815277098386812048 Jayarava

    The other name for a tripartite synapse is “transistor”.

  • http://www.blogger.com/profile/06815277098386812048 Jayarava

    Oh, and it sounds like glia communicate the same way that colonies of bacteria do.

  • http://www.blogger.com/profile/13861718460737399371 Amy

    I spoke to some interesting Australian researchers late last year who had proven that astrocytes die first in neuromyelitis optica (and possibly MS as well, i cant remeber, before the myelin disintergrates.
    Glad to hear more on the topic of glia

  • http://www.blogger.com/profile/08172964121659914379 andrew

    Could it be that glial cells have a role so essential that if it is tinkered with, that the result is death, so that glial cell system disorders are exceedingly rare?

    Psychiatry's phylogeny of disorders may be questionable, but it seems to be quite comprehensive and the vast majority seem to have causes quite apart from glial cells. The limbic system and other neurotransmitter levels seem to be a veritable treasure trove of defects by comparison.

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Neuroskeptic

No brain. No gain.

About Neuroskeptic

Neuroskeptic is a British neuroscientist who takes a skeptical look at his own field, and beyond. His blog offers a look at the latest developments in neuroscience, psychiatry and psychology through a critical lens.

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