Tobias has a creepy-fun blog post up today about Toxoplasma gondii, a parasite that causes rats to become attracted to cats, which can adversely affect the development of a baby within a pregnant women's body. The post digs into Stanford scientist Dr. Robert Sopalsky's research around how "toxo" changes human behavior, but this snippet about how it "hijacks the sexual reward pathway" in rats' minds is pure gold.
Once in the rat, Toxo's goal is to then be eaten by a cat so it can be fruitful and multiply, but as I mentioned, this can only take place in the cat's gut. Toxo's goal is to get the rat eaten by a cat. Toxo could get the desired effect through a whole sort of seemingly obvious ways; e.g., Make the rat hard to run so it is easier for a cat to catch it. Instead it takes a far more interesting approach:
Toxo generates cysts in the brain of the rat. These cysts take over the fear center of the brain, but specifically the fear of predators. Common fear sources for rodents (e.g., bright lights, open spaces, etc.) still operate perfectly well in an infected rat, but now they are no longer afraid of cat piss. That alone would be cool enough, but Toxo takes it one step further. When Toxo is going about futzing with the fear center of the brain it also goes into the sexual excitement part of the brain. It hijacks the incoming Fear of Cat Piss™ and instead diverts the signal to the Barry White™ center of the brain.
"Somehow, this damn parasite knows how to make cat urine smell sexually arousing to rodents, and they go and check it out. Totally amazing." – Dr. Sapolsky
The rat is now sexually attracted to cat piss! (This is a fetish that gets you eaten by your predator and rats clearly do not have any safe words with cats.)
Now, this part blew my non-rat mind: Sapolsky says motorcyclists have a high probability of being infected with Toxo. Read the post to unpack that part.
More about Sapolsky's research on Edge.org.