When Sepiedeh Keshavarzi was getting her medical degree in Tehran, she often read research papers by prominent scientists in the U.S.

"It was my dream at some point when I was much younger to do research in the States," she says.

Not anymore.

The U.S. denied Keshavarzi's request for a visa to attend this year's Society for Neuroscience meeting, which drew more than 25,000 brain scientists from around the world to Chicago this week. She was also denied a visa for last year's meeting in San Diego.

The reason: Keshavarzi holds an Iranian passport, even though she hasn't lived in that country since 2007. Iran is one of seven countries included in President Trump's travel ban, implemented through an executive order.

"I knew there was a travel ban in place," Keshavarzi says, "but I thought there could be an exception because I am a permanent resident of Australia."

Also, she'd been specifically invited to the meeting to give a presentation on special brain cells that help us keep track of our own motion.

So Keshavarzi, who is currently doing research at University College London, sent a prerecorded PowerPoint presentation to the meeting in her stead.

But she says after two years of disappointment, her career goals have changed.

"I will be looking for jobs in a few months and I'm not considering the U.S. anymore, which is a real shame," she says. "I will be only looking in Europe now."

Visa problems have become common enough that the Society for Neuroscience created a program called Science Knows No Borders for this year's meeting. It's aimed at helping scientists like Keshavarzi present their research even though they can't attend.

Another scientist who took advantage of the help was Hamid Ramezanpour, a Ph.D. student at the University of Tübingen in Germany who also has an Iranian passport.

Ramezanpour had been scheduled to present a poster at the meeting showing his research.

The poster sessions take place in an exhibition hall the size of several football fields. At a designated time and place, researchers unfurl their posters and field questions.

But at the appointed time, Ramezanpour was still stuck in Europe. "My poster is luckier than me because it doesn't need a visa to go," he said in a Twitter post.

So Instead of Ramezenpour, people viewing his poster encountered Raymundo Báez, a former colleague who was born in Mexico and is now a researcher at Massachusetts General Hospital in Boston.

"He wanted to come here to, you know, present his work and he wasn't able because his visa was denied," Báez said.

The Society for Neuroscience says fewer than a dozen scientists from Iran, Mexico and India participated in the Science Knows No Borders program this year. But an informal survey of more than a dozen poster presenters found that nearly all of them knew at least one brain scientist who'd been kept away by a visa delay or denial.

And that doesn't include scientists who never made travel plans at all because they hold passports from a banned country.

"People ask me what is the number of those out there affected," says Keshavarzi, "and I keep saying you wouldn't know because they don't apply."

Some scientists persevere, though.

Leili Mortazavi missed last year's neuroscience meeting in San Diego because of her Iranian passport. At the time, she was studying at the University of British Columbia, just a few miles from the U.S. border.

"I showed up with tons of documents and I was just told that because of the presidential travel ban I'm ineligible to even apply for a visa," she says.

So when Mortazavi began job hunting a few months ago, she applied for a Canadian passport.

"I was lucky that I got my Canadian passport just a few days before the interview for Stanford," she says.

A few weeks ago, Mortazavi started her job as a graduate research assistant in a lab at Stanford.

She loves the scientific community there, she says, but has mixed feelings about being in the U.S.

"It's kind of sad to be in a country that has these policies in effect," she says. "I really hope that they change soon."

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