Are you scared of spiders?

The nervous college student was pacing the corridor, so scared of the caged spider at the end of the hall that he thought he would leave before the therapy session began.

After about two hours of "exposure therapy," which involved touching the 5-inch-wide tarantula with a paintbrush, then with gloves and finally with bare hands, he didn't want to leave the arachnid.

"It was so sweet. I remember thinking this was not a problem I had anticipated -- that he wouldn't want to leave the spider," said Katherina Hauner, a post-doctoral neurology fellow at the Northwestern University Feinberg School of Medicine in Chicago.

The patient's phobia was cured. And Hauner was able to observe how the brain changes when fear is successfully treated.

Hauner's research, published this week in the Proceedings of the National Academy of Sciences, documents the immediate and long-term brain changes after treatment for a phobia.

Her 12 arachnophobic subjects underwent brain imaging scans -- while being shown pictures of spiders -- immediately before and after the therapy. The same scanning technique was performed six months later.

Brain scans after the therapy showed that regions associated with fear had decreased activity when the subjects were shown pictures of spiders. The scans also showed how the brain reorganizes long-term to reduce fear.

"It is not about spider phobia results, but about fear extinction in general," said Hauner, 33, who was a psychology graduate student when she conducted the spider research in 2009 and 2010.

Hauner purchased the hairy tarantula at a pet store and named her Florence in honor of an administrative assistant in the psychology department who had a gentle demeanor.

"I thought it would fit what I was hoping people would think about the tarantula," Hauner said.

The participants, recruited through campus posters asking for people who wanted to overcome their fear of spiders, were so afraid of arachnids that they would avoid grass or stay out of their homes or dorm rooms if one was lurking.

When the subjects were first shown spider pictures while undergoing MRI scans, the parts of their brains associated with fear lit up with activity. When they were asked to approach a closed terrarium, they couldn't get closer than 10 feet on average. One participant broke out in hives on her neck when she entered the brain imaging machine, just knowing she would be viewing spider pictures.

"I would say they are like bunny rabbits. No one would believe me," she said.

Then, in what's called "exposure therapy," Hauner gradually introduced them to the spiders. They first touched the glass on the outside of the terrarium and, after a 14-step process, all of them pet the spider.

When they returned six months later, all of the participants touched the tarantula. Their arachnophobia hadn't returned. And brain scans showed changes.

"The brain had reorganized itself in a different way to maintain that fear extinction," Hauner said.

Steve Sullivan, the senior curator of urban ecology at Chicago's Peggy Notebaert nature museum, said he has also watched as people gradually warm up to spiders and snakes when they're introduced at shows.

Hauner said she heard from several of the participants after the therapy.

One e-mailed her to say that she saw a spider in her bathtub, and wasn't afraid. Another said he was so proud of overcoming his fear that he planned to get a tattoo of a spider.

As for Florence the spider? She was given to a little boy whose pet spider, of the same breed, had died.