Cat parasite makes people act like cats

OK, this is just weird. But on the topic of modulating normal brain activity, I have to point out this article in the Times Online (UK).

Dangerrrr: cats could alter your personality
THEY may look like lovable pets but Britain's estimated 9m domestic cats are being blamed by scientists for infecting up to half the population with a parasite that can alter people's personalities.
The startling figures emerge from studies into Toxoplasma gondii, a parasite carried by almost all the country's feline population. They show that half of Britain's human population carry the parasite in their brains, and that infected people may undergo slow but crucial changes in their behaviour.
Infected men, suggests one new study, tend to become more aggressive, scruffy, antisocial and are less attractive. Women, on the other hand, appear to exhibit the "sex kitten" effect, becoming less trustworthy, more desirable, fun-loving and possibly more promiscuous.

Here's another weird thing: the parasite is passed cyclically from cats to rats, and when rats are infected, they tend to lose their natural fear of cats. But the effects on humans are subtle and very interesting:

The study into more subtle changes in human personality is being carried out by Professor Jaroslav Flegr of Charles University in Prague. In one study he subjected more than 300 volunteers to personality profiling while also testing them for toxoplasma.
He found the women infected with toxoplasma spent more money on clothes and were consistently rated as more attractive. "We found they were more easy-going, more warm-hearted, had more friends and cared more about how they looked," he said. "However, they were also less trustworthy and had more relationships with men."
By contrast, the infected men appeared to suffer from the "alley cat" effect: becoming less well groomed undesirable loners who were more willing to fight. They were more likely to be suspicious and jealous. "They tended to dislike following rules," Flegr said.
He also discovered that people infected with toxoplasma had delayed reaction times -- and are at greater risk of being involved in car accidents. "Toxoplasma infection, could represent a serious and highly underestimated economic and public health problem," he said.

In other words, whatever this parasite is doing, it is hooking into the natural human neural processes and modulating them in ways that alter otherwise normal outputs. In some respects, it appears alcohol-like by reducing inhibitions and reaction times. In others, it is highly distinctive. But most interestingly, it is distinctive in ways that are clearly related to the regulation of social interactions. In other words, the parasite exerts the (apparently accidental) effect of driving human mental processes slightly haywire.

One startling fact to emerge from research is the great differences in levels of infection. In France and Germany, for example, about 80%-90% of people are infected -- nearly twice that in Britain or America.
"I am French and I have even wondered if there is an effect on national character," Berdoy said.
Dr Dominique Soldati, a researcher at Imperial College in London, is studying ways of blocking toxoplasma from getting into cells. "Once you are infected you cannot get rid of this parasite and the numbers of them slowly grow over the years," she said. "It's not a nice thought."

There's not a one-liner that even approaches this one...