All the ways to screw up a cat's eyesight using science

After last week's blind kittens in carousels, I thought I was done with creepy kitten vision experiments. It turns out, there's a whole genre of them, and most of them deal in stripes.

Exactly how much the brain is preprogrammed, and how much can be reprogrammed, has always been a matter of debate. Insight into what we can deliberately do, and undo, to our brains could shape human capability. For the moment, though, it just seems like a reason to be absolute assholes to cats. For the past few decades, scientists have been researching the effects of "selective rearing." Selective rearing looks at the way extreme conditions during the early stages of life can affect the brain both functionally and physiologically. Because cats develop so quickly, they're often used for selective rearing experiments.

The Vertical and the Horizontal

The most famous experiments deal with vertical and horizontal stripes. Different litters of kittens are raised in darkness. Some of the kittens are let out into the light part of the time — but with cups over their eyes that only allow them to see vertical stripes. Others are only allowed to see horizontal stripes.

In the late 1970s and early 1980s, the cats were generally euthanized afterwards, and their brains examined. The parts of the brain dealing with vision were structured differently in the experimental cats than they would be for ordinary cats. They were not destroyed, but had specific structures built up, depending on whether the cat saw horizontal or vertical stripes.

Can Cats Change Their Stripes?

In the 1990s, the name of the game became neural plasticity, not merely neural structure. Scientists wanted to know if the brain could regain the functions it lost. The experiments were repeated. Cats were raised in darkness, but let out to see only vertical stripes, only horizontal stripes, or different stripes for each eye. This time, the cats were allowed to grow up and their behavior was observed.

The cats moved jerkily, and were more klutzy than other cats. They seemed to have real problems seeing contours that were at right angles to the lines they saw as kittens. Vertical kittens had a hard time seeing horizontal edges and horizontal kittens had a difficult time seeing vertical ones. Just to round out the experiments, one study had kittens only exposed to strobe light. This made it hard for them to learn to make continuous retinal movement. These cats seemed motion blind, and couldn't easily distinguish moving objects. Yes, they were like the dinosaurs in Jurassic Park, except furry and pitiful.

We know that there is such a thing as neuroplasticity — and that the human brain does change and grow after childhood. Looking at the cats, though, it seems we don't entirely grow out of setbacks, or out of selective rearing. Perhaps one day, we'll be able to retrain our brain the way we do when we're first discovering the world throughout our life. Until then, stay away from vertical stripes.

[Via Psychology, Journal of Comparative Neurology, Journal of Neurophysiology]