Parasites and free will

Robert Sapolski in The Edge:

"The parasite my lab is beginning to focus on is one in the world of mammals, where parasites are changing mammalian behavior. It's got to do with this parasite, this protozoan called Toxoplasma. ...

In the endless sort of struggle that neurobiologists have — in terms of free will, determinism — my feeling has always been that there's not a whole lot of free will out there ...

And it's got to do with this utterly bizarre world of parasites manipulating our behavior. It turns out that this is not all that surprising. There are all sorts of parasites out there that get into some organism, and what they need to do is parasitize the organism and increase the likelihood that they, the parasite, will be fruitful and multiply, and in some cases they can manipulate the behavior of the host."

Much has been written on the dangers of Toxoplasmosis for pregnant women and the fetus. As usual, Wikipedia has a good rundown. While not exactly new information, Sapolski does a good job of spelling out the potential (but speculative at this stage) behavioural effects of Toxoplasmosis infections in mammals, more specifically humans. It turns out that the parasite, through a common evolutionary ancestor billions of years ago, is able to manipulate very specific circuits in the mammalian amygdala that control stress responses to predators. In the case of rats, their natural avoidance and fear reaction to cat urine is replaced by attraction and mild sexual stimulation. Oops ...!

Thinking of a number of tourists the last few years who stupidly (fatally) approached lions in South African game reserves, one wonders whether they were infected by Toxoplasmosis and actually died in sexual euphoria?! OK, maybe that's taking it a bit too far. The important issue remains that this is another possible factor that may be affecting our behaviour and makes free will an ever more elusive phenomenon.

Now, where's that damn cat?