What happened to the cat with dry skin? Purrrrritus.

I've often wondered why we scratch itches. If you think about it from an objective point of view, it doesn't make any sense to scratch. If anything, it only irritates the skin more. So why does it feel good? Thankfully, the back page of Scientific American, bringer of useless yet fascinating information, had a short article explaining it. Turns out that the "pruritus" (note quotation marks for fancy Latin name for itching) neurons are separate from "pain" and "rubbing" (note quotation marks for non-fancy non-Latin names for pain and rubbing) neurons. Because of a local inhibitory effect, these neurons trump the pruritus sensors, temporarily relieving the itching sensation. The itching arises in the first place from things like dryness and chemical irritation.

Maybe it could work the other way. We could be treating soreness and pain with poison ivy, or something, if the pruritus sensory neurons can also inhibit the pain ones.

Also, "pruritus" is an incredibly tough word to pronounce. It's like "rural," but harder. I can only imagine trying to say it in French; I think I'd need some Halls afterwards.

Then why do casinos make money?

This Nature article fits perfectly with my current neurology kick. Everybody's heard of Pavlovian experiments, where an animal is trained to produce a physiological response to a normally unrelated stimulus by repetition. In Pavlov's case, he simply rang a bell and fed steak, and over time was able to induce salivation by ringing the bell only.

That's all well and good, but this paper asks what happens when ringing the bell is only assigned a probability of bringing steak. They showed four of ten shapes to monkeys, and then allowed to look at either a green or red target. Each shape carried a probability with it of a reward being given for a red or green choice. They were then able to train the monkeys to select red or green based on the most likely outcome, given the shapes presented.

The paper focuses heavily on the neurons in the parietal lobe involved in probabilistic reasoning. That's where the statistics get a little too dense for me, but I find the concept interesting; they were able to demonstrate the region of the brain associated with logic based on probabilities, rather than proven results.