News of the Not So Wierd

Since cats don’t want to eat dead, decaying prey, Toxoplasma takes the evolutionarily sound course of being a “good” parasite, leaving the rats perfectly healthy. Or are they?

Oxford scientists discovered that the minds of the infected rats have been subtly altered. In a series of experiments, they demonstrated that healthy rats will prudently avoid areas that have been doused with cat urine. In fact, when scientists test anti-anxiety drugs on rats, they use a whiff of cat urine to induce neurochemical panic.

However, it turns out that Toxoplasma-ridden rats show no such reaction. In fact, some of the infected rats actually seek out the cat urine-marked areas again and again. The parasite alters the mind (and thus the behavior) of the rat for its own benefit.

If the parasite can alter rat behavior, does it have any effect on humans?

Dr. E. Fuller Torrey (Associate Director for Laboratory Research at the Stanley Medical Research Institute) noticed links between Toxoplasma and schizophrenia in human beings, approximately three billion of whom are infected with T. gondii:

* Toxoplasma infection is associated with damage to astrocytes, glial cells which surround and support neurons. Schizophrenia is also associated with damage to astrocytes.
* Pregnant women with high levels of antibodies to Toxoplasma are more likely to give birth to children who will develop schizophrenia.
* Human cells raised in petri dishes, and infected with Toxoplasma, will respond to drugs like haloperidol; the growth of the parasite stops. Haloperidol is an antipsychotic, used to treat schizophrenia.

Dr. Torrey got together with the Oxford scientists, to see if anything could be done about those parasite-controlled rats that were driven to hang around cat urine-soaked corners (waiting for cats). According to a recent press release, haloperidol restores the rat’s healthy fear of cat urine. In fact, antipsychotic drugs were as effective as pyrimethamine, a drug that specifically eliminates Toxoplasma.

Are parasites like Toxoplasma subtly altering human behavior? As it turns out, science fiction writers have been thinking about whether or not parasites could alter a human being’s behavior, or even take control of a person. In his 1951 novel The Puppet Masters, Robert Heinlein wrote about alien parasites the size of dinner plates that took control of the minds of their hosts, flooding their brains with neurochemicals. In this excerpt, a volunteer strapped to a chair allows a parasite to be introduced; the parasite rides him, taking over his mind. Under these conditions, it is possible to interview the parasite; however, it refuses to answer until zapped with a cattle prod.

He reached past my shoulders with a rod. I felt a shocking, unbearable pain. The room blacked out as if a switch had been thrown.. I was split apart by it; for the moment I was masterless.

The pain left, leaving only its searing memory behind. Before I could speak, or even think coherently for myself, the splitting away had ended and I was again safe in the arms of my master…

The panic that possessed me washed away; I was again filled with an unworried sense of well being…

“What are you?” “We are the people… We have studied you and we know your ways… We come,” I went on, “to bring you peace.. and contentment-and the joy of-of surrender.” I hesitated again; “surrender” was not the right word. I struggled with it the way one struggles with a poorly grasped foreign language. “The joy,” I repeated, “-the joy of . . .nirvana.” That was it; the word fitted. I felt like a dog being patted for fetching a stick; I wriggled with pleasure.

Still not sure that parasites can manipulate the behavior of host organisms? Consider these other cases:

* The lancet fluke Dicrocoelium dendriticum forces its ant host to attach to the tips of grass blades, the easier to be eaten. The fluke needs to get into the gut of a grazing animal to complete its life cycle.
* The fluke Euhaplorchis californiensis causes fish to shimmy and jump so wading birds will grab them and eat them, for the same reason.
* Hairworms, which live inside grasshoppers, sabotage the grasshopper’s central nervous system, forcing them to jump into pools of water, drowning themselves. Hairworms then swim away from their hapless hosts to continue their life cycle.

Not all science-fictional parasites are harmful; read about the Crosswell tapeworm from Brian Aldiss’ 1969 story Super-Toys Last All Summer Long (the basis for the Kubrick/Spielberg film AI), which keeps people who overeat from becoming obese. Not to mention robots based on parasites. Read press release on evidence for link between Toxoplasma and schizophrenia, Suicidal grasshoppers. Story via blogger Carl Zimmer and his readers.

(This Science Fiction in the News story used with permission from Technovelgy.com – where science meets fiction.)

* Fine Line Revealed Between Creativity and Insanity
* Brain Breakthrough: Scientists Know What You’ll Do

So what makes a hit?

A new study reveals that we make our music purchases based partly on our perceived preferences of others.

Popularity contest

Researchers created an artificial “music market” of 14,341 participants drawn from a teen-interest Web site. Upon entering the study’s Internet market, the participants were randomly, and unknowingly, assigned to either an “independent” group or a “social influence” group.

Participants could then browse through a collection of unknown songs by unknown bands.

In the independent condition, participants chose which songs to listen to based solely on the names of the bands and their songs. While listening to the song, they were asked to rate it from one star (“I hate it”) to five stars (“I love it”). They were also given the option of downloading the song for keeps.

“This condition measured the quality of the songs and allowed us to see what outcome would result in the absence of social influence,” said study co-author Matthew Salganik, a sociologist at Columbia University.

In the social influence group, participants were provided with the same song list, but could also see how many times each song had been downloaded.

Researchers found that popular songs were popular and unpopular songs were unpopular, regardless of their quality established by the other group. They also found that as a particular songs’ popularity increased, participants selected it more often.

The upshot for markerters: social influence affects decision-making in a market.

This research is detailed in the Feb. 10 issue of the journal Science.

The Britney effect

The social-influence group was further divided into eight separate, non-interactive “worlds.” Members of each world could not see the decisions of the other seven. The idea behind this was to observe multiple outcomes for the same songs and bands.

“If you look at Britney Spears, some people say she is really good. Others say she isn’t good, she’s just lucky,” Salganik told LiveScience. “But by having just one argument, it’s impossible to distinguish. However, if you have 10 worlds, and she’s popular in all 10, then you can say she’s actually good. But if she’s only good in one, then you could say it was due to luck.”

Although different songs were hits in each world, popularity was still the deciding factor, although the “best” songs never did very badly and the “worst” songs never did very well.

So what drives participants to choose low-quality songs over high-quality ones?

“People are faced with too many options, in this case 48 songs. Since you can’t listen to all of them, a natural shortcut is to listen to what other people are listening to,” Salganik said. “I think that’s what happens in the real world where there’s a tremendous overload of songs.”

Alternatively, Salganik said, a desire for compatibility with others could drive the choice, since much of the pleasure from listening to music and reading books stems from discussing them with friends.