[ExI] Infrared vision via vitamins (well, not really)
rpicone at gmail.com
Thu Jul 15 03:57:15 UTC 2010
On Fri, Jul 9, 2010 at 1:11 PM, Bryan Bishop <kanzure at gmail.com> wrote:
> Infrared vision with vitamins
> Although I've mostly been interested in sensory augmentation by means
> of technology, there was an interesting third-hand report of
> augmentation through diet and biochemistry. The military during WWII
> (there are mentions of both US and British forces) evidently
> experimented with putting people on diets that replaced the normal
> form of vitamin A with a slightly different chemical, in the hopes
> that the red-sensitive photopigment in the retina constructed from it
> would be changed to a chemically similar form, present in other
> animals, with spectral sensitivity extending into the near infrared.
> The idea, of course, was to be able to see signal lights and so forth
> that were invisible to enemy soldiers.
> I did some quick checking on this, and though I couldn't find any
> references to military research, there were some examples in the
> regular civilian literature. Yoshikami, Pearlman, and Crescitelli
> (Vision Research 9:633-646 1969) did a similar experiment on rats,
> putting them on a diet which was deficient in vitamin A and
> supplementing it with additions of either vitamin A1 (the normal form)
> or A2 (the altered one). No behavioral studies were done, but they did
> extract the retinas and perform some spectral analysis, with the
> result that there was indeed some alteration of the photopigments,
> specifically the addition of a second form with sensitivity shifted
> redward by about 20nm.
> That study cited Millard and McCann (Journal of Applied Physiology
> 1:807-810 1949) which was an experiment on humans, albeit with fairly
> loose controls on diet. They found that behaviorally the group taking
> A2 supplements had slightly improved red sensitivity, but didn't
> provide any detailed spectral response curves.
> So it seems to be the case that this effect is real, but small: the
> best you can hope for is a shift of about 20nm, which is not really
> enough to be of military significance or even detectable without
> careful testing. Still, it's an interesting "hack" on human
> What wavelength spectrum would you want to get up to- near infrared?
> far? There was an article recently about cryptochrome, a protein in
> avian retina for sensing magnetic fields. I can think of a few designs
> for experiments for improving infrared vision, maybe through directed
> evolution of (tethered?) photopigments.
Technically you already have pretty decent near infrared, just only in your
cones and not your rods, making all reds much harder to see and less vivid
in low-light environments. Vitamin A only affects rod photopigments, which
IIRC cut off around 650 nm, where infrared is typically considered to start
at 700 nm and most people can see up to 750 nm or so in the right
environments (though those environments aren't exactly typical, thanks
either to some nuance of the multi-stage opponent process our eyes use, or a
simple lack of sufficient pupil dilation objects that reflect light just
beyond 700 nm may look black unless viewed through goggles with IR-pass
filters or under direct near-infrared light in a dark environment. A lot of
manmade black pigments do this actually.)
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