Optogenetics: light on brains

By Grant Jacobs 18/05/2011 11


Optogenetics lets researchers directly examine the brain through controlling neurons in the brain by inserting genes for particular photoreceptors, proteins that respond to light, into neurons.

But let Ed Boyden explain it.* He gives an excellent presentation, with great visuals:

Footnotes

* I’ve presented a video on this topic before, but it thoroughly deserves fresh viewing. This earlier post also has my own brief description of optogenetics. Ed covers this ground in his talk.

You’ll notice Ed Boyden briefly mentions cochlear implants in his talk – something I still haven’t written about. One day…


Some other neuroscience-related articles on Code for life:

Autism genetics, how do you copy?

Neurological shorts

Understanding the brain through controlling it

The inheritance of face recognition (should you blame your parents if you can’t recognise faces?)

I remember because my DNA was methylated


11 Responses to “Optogenetics: light on brains”

  • I think you need to work on your opening sentence a bit, Grant: it needs a grammar tweak. Apart from that, I’ve a question that has puzzled me for a while: the human brain has several hundred billion neurons. Fine. If we evolved a new neuron every day, from nothing, surely it would take a hundred million years to get as many as we have now?
    Where do they all come from? I understand that we grow from a single cell to our total several trillion cells in ten years, and those trillion are all planned, but the planning is what needs to evolve, chilralic molecule by chiralic molecule.
    How so?

  • If we evolved a new neuron every day, from nothing, surely it would take a hundred million years to get as many as we have now?

    You’re assuming brain expansion one neuron at a time – bad assumption. (This is the reason I believe that, contrary to what you say, you haven’t thought much about this at all.)

    There are at least three errors here, all of them common from creationists on-line (and presumably off-line also, but I wouldn’t know):

    => not allowing for independent evolution of adjacent regions, e.g. one region of the brain can expand independently and at the same time as others also changing. (This gives a numbers game with similar properties to your growth of body example.)

    => presuming a “pre-destined number of cells” doesn’t reflect how tissues actually grow. Tissues grow under control of regulatory molecules. Change the regulatory molecules, or how they work, and evolution can rapidly affect how an organ grows. (To develop neuron by neuron as you suggest, each step would have to be a pre-ordained exact “magic number” of neurons, but that’s not how tissues grow. The “pre-destined number of cells” notion in this context is a ‘design’ notion inaccurately imposed on biology.)

    => not allowing for evolution acting on larger units. Like all organs, the brain is full of substructures, which have been re-used during evolution with variations on their basic theme. The most obvious example is that our brains have two hemispheres that are more-or-less mirror duplicates. There are many other substructures, right down to arrays of adjacent neurons. The thing here is that evolution doesn’t have to just “add” one neuron at a step, it can “add” multiple copies of larger substructures (or single cells for that matter) in a single evolutionary change. (The details of this lie in my previous point.)

    chilralic molecule by chiralic molecule

    Editing errors happen (as in my case), but ‘chilaric’ isn’t even a word 😉 (You want chiral.) On this note, I would gently suggest you take care in poking at other’s editing errors, typos, etc.; you’ll only find yourself doing worse and looking silly for it.

    More importantly, chiral molecules have nothing to do with this. You appear to be putting forward a phrase you’ve read in your creationist literature without understanding it’s relevance and when it might apply.

  • Well, all very true. But your assertion that the brain’s substructures have been reused by evolution is merely a just-so statement, unless you can substantiate it by showing more than the mere existance of such structures.
    Nevertheless, it still holds true mathematically, that such a collosal amount of genetic change would need enormous amounts of time to happen, ergo Francis Crick, Dawkins et al plumping for aliens to explain it. These people are your visionary leaders, and they have rejected an evolutionary beginning on earth. Do you claim they are mistaken?

  • On a slightly related note (for all readers), this article I ran into earlier in the week is excellent (the guy’s an excellent writer):

    http://scienceblogs.com/neurophilosophy/2011/05/a_whiff_of_early_brain_evolution.php

    gjphilip:

    But your assertion that the brain’s substructures have been reused by evolution is merely a just-so statement,

    So is your statement that brain evolved neuron by neuron.

    unless you can substantiate it

    Care to substantiate that brains expanded single neuron by single neuron? (Your claim.)

    What I’m pointing out is that you’re playing a two-faced game, asking for “evidence”, without offering any for your claim; pointing at just-so statements, but only offering just-so statements yourself. (Pot calling kettle black, etc.)

    In order to show that brain evolution isn’t bound to your neuron-by-neuron model I only have to point to a better model that’s reasonable.

    it still holds true mathematically, that such a collosal amount of genetic change would need enormous amounts of time to happen

    Not true. I really suggest you learn some biology before making claims like that. In fact, answered an aspect of this in my earlier reply to you: Tissues grow under control of regulatory molecules. Change the regulatory molecules, or how they work, and evolution can rapidly affect how an organ grows. The same applies to changing the portions of DNA the regulatory factors act on – small localised changes to regulatory regions and regulatory molecules can have major effects.

    ergo Francis Crick, Dawkins et al plumping for aliens to explain it.

    No, they didn’t. This seems to be a ‘standard’ myth that creationist groups tell each-other. Aside from that these researcher’s speculations on the origin of life referred to here are from the 1970s – early 1980s, and that they have shifted their positions since (which creationist sources seem to want to ‘overlook’), and that this leaves out great swathes of more recent relevant findings (in particular a better understanding of RNA in molecular biology that simply wasn’t around in those days), there is a difference between ‘alien life’ and ‘aliens’! They referred to *alien life* referring to the idea of bacteria, viruses, etc. from other planets, not ‘aliens’ as in some science fiction novel with their little green men or “intelligent life in space” or “intelligent life in somewhere out there”.

    (I saw that Ian Wishart parroting this line the other day, too. I have to admit I wasn’t very impressed.)

    These people are your visionary leaders, and they have rejected an evolutionary beginning on earth. Do you claim they are mistaken?

    Creationism promotes the fallacy of ‘the appeal to authority’ because religions need it. Science focuses on the claims not the people as you are doing. Besides: would you care to substantiate the existence of aliens (your claim, not theirs) to move it past a just-so statement? 😉

    I have a very heavy workload until at least next week, so I’m unlikely to be able to take this further. You might try looking for your own answers instead of pleading for others to counter your religious-based views. (You won’t find them on religious websites, though.)

  • ergo Francis Crick, Dawkins et al plumping for aliens to explain it.
    As Grant says, no, they didn’t. (& I seem to remember explaining this on one of my own posts, earlier this year.) The Dawkins claim relates to an extremely dishonest interview done for the film “Expelled” (although that’s not what Dawkins was told it was for) during which he was asked about the possibility of aliens being involved with the evolution of terrestrial life. To which he responded that as a scientist he could never absolutely rule out such possibilities, but that it was unlikely in the extreme. He explicitly does not “rule out evolution”, despite the efforts of Ben Stein et al to put that construction on his words.

    Interesting that the creationist lobby feels it necessary to stoop to such intellectual dishonesty in attempting to support their point of view…

  • Thanks for filling us in Alison. Your take on this will be much more accurate and informed than mine! I have to admit these days I rarely have much idea where these rumours/myths/quote-mines originate. I’m impressed you can keep up with it! (I can vaguely recall PZ Myers writing about that interview, or perhaps it was Orac – ? It’s the sort of thing that they cover well.)

  • Well, thanks for your time. I do have a lot of respect for your work, and appreciate your allowing an outsider to the cause, such as myself, the right to ask questions.
    With respect to the alien life issue, you may, upon reflection, see that aliens and alien microbes are the same thing. The difference between conscious aliens , or liitle green men, and alien microbes is very small given the stupendous complexity of the living cell. The unimaginably huge evolutionary gap seems to be between cells and non-cells, if current microbiology is correct.

  • With respect to the alien life issue, you may, upon reflection, see that aliens and alien microbes are the same thing.

    No. It’s misrepresenting these people, basically put: lying.

    A good, sensible rule of thumb for this sort of thing is that unless it’s explicitly stated the common meaning will rule. Everyone knows what the common meaning of ‘alien’ is. It’s nothing like bacteria.

    Pointing at the origin of life doesn’t make the misrepresentation go away. (It essentially amounts to trying to divert attention from the lie. I’d like to think that most members of an organisation that lied as blatantly as this would think twice about the organisation they’re in.)

    The unimaginably huge evolutionary gap seems to be between cells and non-cells, if current microbiology is correct.

    You mean your particular interpretation of microbiology.

    (While I’m writing: there is a roughly a couple of billion years of time in the fossil record between prokaryotic life and eukaryotic life, let alone complex eukaryotic life.)

  • nature abounds with examples of major steps in development. In fact evolution can progress in two modes, incrementally and in larger steps. There is plenty of evidence for both modes occurring all around us. Here are some examples – I think this illustrates how easy it is to evolve in large steps: http://www.macroevolution.net/prevalence-of-polyploidy.html
    Even single point mutations can have an enormous systemic effect. A very prominent example for one of these is the Belgian Blue mutation in cattle. The Belgian Blue was the result of crossing two cattle breeds, but no technology was involved. The pictures illustrate how a single nucleotide mutation can change an animal almost beyond recognition, Look at these photos: http://www.hemmy.net/2007/07/16/belgian-blue-cattle-super-cow-aka-incredible-hulk-cow/
    Evolution in giant leaps occurs all around us and lives happily alongside a much more incremental process.

  • SAB,

    Thanks for the examples. Your examples illustrate the wider point nicely, I think.

    I can remember when I first saw a photo of a Belgian Blue and almost physically taking a step backwards – they’re big beasts! (The photo of ‘Wendy the Whippet’ that article links to is impressive, too.)

    Polyploidy, and other large-scale duplication events, are good examples of rapid increase in genetic material. Just as there is no need for brains to have evolved “neuron by neuron”, genes don’t “have” to arise one at a time either. For that matter, it is generally considered that our own genomes are a four-fold duplication of an ancestral genome.

    [Minor edit with quirky story behind it: pushed comment out knowing it had an error as the keyboard had locked up and preferred to have the comment go out rather than have to re-type it…]

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