I had the good fortune to sit next to a very interesting gentleman on the plane. He was in his late twenties, wearing a thin V-neck T-shirt with fashionable glasses, reading a hardcover book with an outline format. To ascertain whether I should reach for the cross I keep around to ward off the unholy, I asked if he was a law student. “No”, he said, “I’m a philosophy teacher”. Phew.

We then had an interesting conversation regarding the nature of perception, his area of study. Luckily, I was primed for this discussion, as at the exact moment I was reading A Brief Tour of Conciou5ness* [sic], a survey of fascinating neurological phenomena and what they can tell us about the brain. We mainly talked about “blind sight”, the (controversial) finding that individuals who have blindness-causing brain damage (cortical blindness) can point to the location of a light correctly almost every time, despite the fact they claim they are just guessing.

The theory behind blind sight is that a secondary visual area is able to “know” limited information about the environment and can influence behavior, but doesn’t connect to our consciousness. One explanation for this ability is that it’s enhanced or even induced after injury, similar to the increased hearing acuity of blind individuals. I’ll consider this a possibility but ignore it for now because I find it less interesting. In the case that there isn’t any post-injury enhancement, all humans have the same capacity to “see” some things without being aware of it.

Assuming that this pathway is still active in uninjured individuals, what could it be used for? One argument is that it’s residual, more important in primitive animals, and survives now as a sort of biological parlor trick. My limited intuition on the subject shrinks at this. Capacities that are unused in an organism are generally selected against and removed. For example, multiple populations of dark-dwelling, underground cavefish in Mexico have evolved stunted eye development, and this in only 10,000 years. So this secondary sensory pathway should do something, but what? A curious scientist (ahem) would slice the pathway in a mouse and see what happens. But to keep murine casualties at a minimum, it would be nice to have a couple hypotheses ready.

First, it’s possible that the secondary visual pathway processes information faster than the primary route. In this case, we would expect intact mice to respond more quickly to a dangerous stimulus than mice without the intact pathway. Alternatively, it could be that the secondary route has less of a filter on incoming information, and can perceive subtler sources of danger.

I’m studying mouse eyeballs, so mouse brains are safe….for now.

V.S. Ramachandran. (2004). New York: Pi Press