Wednesday, September 30, 2009

Drinking a Reward

In a mere 20 weeks previously color blind monkeys appear to have become trichromats through a subretinal injection of a virus containing L-opsin (1).

At the end of this paper, the authors assert: "we do know that evolution acts on behaviour, not on internalized experiences, and we suggest that gene therapy recapitulated what occurred during evolution of trichromacy in primates. These experiments demonstrate that a new colour-vision capacity, as defined by new discrimination abilities, can be added by taking advantage of pre-existing neural circuitry and, internal experience aside, full color vision could have evolved in the absence of any other change in the visual system except the addition of a third cone type."

Which is to say the results are not just about curing monkey color blindness.

The term plasticity is used in several places although it is noted that "it is possible that it exploited the pre-existing blue-yellow circuitry". But if this is the case it's almost as if the rAAV2/5 vector with L-opsin is more like a perceptual parasite of sorts. Neural wiring and retinal real estate that was previously devoted to other receptors is now taken up by the L-opsin.

And then trichromacy occurs.

Or at least in behavioral assessments of monkeys using juice, the monkeys get to drink around 30% more juice because of lowered thresholds between 485 and 500 nm. Amazing.

(1) K. Manusco, W.W. Hausworth, Q. Li, T.B. Connor, J.A. Kuchenbecker, M.C. Mauck, J. Neitz and M. Neitz, "Gene Therapy for red-green colour blindness in adult primates", Nature (2009) of the Neitz Color Vision Molecular Genetics Lab.