A Look Inside A Brain

By Neuroskeptic | March 18, 2011 2:25 pm

A remarkable paper just out in Nature has revealed images of the brain’s structure and function in unprecedented detail: Network anatomy and in vivo physiology of visual cortical neurons.

Harvard Medical School researchers Bock et al took a mouse – just one – and used two forms of microscopy to investigate a small patch of it’s primary visual cortex, the area which receives input from the eyes.

First, they used two-photon calcium imaging to look at the functional properties of individual cells. They displayed various kinds of patterns in front of the mouse’s eyes, and looked to see which cells lit up, using a special dye which become fluorescent in the presence of calcium, which rises inside cells when they fire.

Having done that they took the same chunk of cortex (a rough cube of about 0.4 mm on each side) and used electron microscopy to see it in its entirety. This was the tricky part. Electron microscopy only works if the sample is first cut into extremely thin slices. Each of the 1,200 slices took 20 minutes to image so in total they spent “several months” to get it all done, using a home-made device consisting of 4 high-resolution digital cameras that fed the information to an image processing system.

In total, they acquired 36 terabytes of electron microscope images, and after processing it all they ended up with a 3D picture of 10 million megapixels. My phone has a 16 GB internal storage and a 5 megapixel camera, so in order to get this data I would have to take 2 million photos, and it would take over 2000 phones to store them. There isn’t an app for that…yet.

The end result was some very pretty pictures, and amazing movies. Oh, and also, some science – they were able to compare the functional properties of brain cells to their actual physical wiring diagram. This, in the broadest sense, is what all neuroscientists are trying to do; Bock et al, however, went out and did it directly.

They were able to test an important hypothesis, namely that in the visual cortex, pyramidal cells (the main cortical cell type) project to inhibitory GABA interneurons in a manner which doesn’t depend on their orientation-selectivity – whether they respond most strongly to seeing vertical lines, horizontal lines, diagonal ones, etc. Bock et al found that this seemed to be true: pyramidal cells synapsed onto whichever GABA cells happened to be nearest to them, regardless of their orientation-selectivity.

Still, it took them several months to image an area containing just 1,000 neurons. The mouse cortex has 4 million, and the human cortex has 11,000 million, so this is a tiny fraction of the whole brain, and the small size of the area meant that they were only able to examine short-range connections between neighbouring cells, not long-range wiring. So this is early days, but it’s clearly an extremely exciting technique and is sure to open the way to major advances in the future.

Link: Also blogged at Brains Lab.

ResearchBlogging.orgBock DD, Lee WC, Kerlin AM, Andermann ML, Hood G, Wetzel AW, Yurgenson S, Soucy ER, Kim HS, & Reid RC (2011). Network anatomy and in vivo physiology of visual cortical neurons. Nature, 471 (7337), 177-82 PMID: 21390124

CATEGORIZED UNDER: papers, science
  • Anonymous

    This kind of research is fascinating and mirrors what is going on in cosmology and astronomy. Just as we are imaging our brains, our Hubble telescope and other NASA probes are doing the same for the universe. The images produced are eerily similar, in some respects. Our brain has 11,000 million neurons in the cortex? That's kind of like the billions and billions of stars and galaxies that are posited to exist. It may be that our universe is one gigantic “brain” and quite probably organic in nature; and we here on earth are a mere galactic neuron. Maybe when we solve the riddles of the universe we will also solve the same for the brain. But it will probably take another billion years to do so! If ever.

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

    A good summary of that research – I like the comparison of the data size to your phone :-).

    Should it not be 100 billion neurons rather than 11 billion? That's my understanding, and it's also the number on the Wikipedia page you reference.

    @anonymous Our galaxy has about 200 billion stars, but no synapses as far as we know. So, it's a nice analogy, but breaks down fairly quickly.

  • Anonymous

    Hey Jayarava: Give me a break. I was stoned when I wrote that! And I still like the analogy. And maybe worm holes are synaptic transmission sites.

  • http://www.blogger.com/profile/07314450642021911177 Andy McKenzie

    Thanks for the link! I'm a longtime neuroskeptic reader. Agree that the field has a ways to go, but has lots of promise.

    One advantage of your anonymity is that you are probably a little less reluctant to break Nature's non-creative commons stance. :)

  • veri

    Anon, dude.. if you're referring to astral projections, out-of-body experiences, third eye and so on remember to keep it confined to those metrosexual new age teaching sessions like 'critical thinking' and not a NASA briefing. Maybe if we all critically evaluated things more we'd bond all our synapses together and kumbaya to mars.

    Having said that though I recall reading somewhere about mini black holes.. which may explain the possibility of time travel through the mind like a shaman, prophet etc. I wonder if that tedious nissl? stain collective can digitally predict time travel based on certain pattern projections.

    The images are probably too glunky yet but maybe in the future they’ll come up with algorithms which can manipulate and smooth out distortions to predict an artificial possibility. Could you imagine.. a prophetic computer.. although computers are already making predictions based on mathematical projections, I wonder if it's possible to do so when it’s comprised of digital organic substrates based on the human brain.. like a brain mirror, organic robocop.

    Being stoned ain't kosher wail more religion is an opiate for the masses, but those images are totally hot and making me hungry.

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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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