The U.S. released a top Iranian scientist Mojtaba Atarodi in April as part of the dealings with Iran in Geneva recently, the Times of Israel reported.

The secret back channel of negotiations between Iran and the United States, which led to this month’s interim deal in Geneva on Iran’s rogue nuclear program, has also seen a series of prisoner releases by both sides, which have played a central role in bridging the distance between the two nations, the Times of Israel has been told.

In the most dramatic of those releases, the US in April released a top Iranian scientist, Mojtaba Atarodi, who had been arrested in 2011 for attempting to acquire equipment that could be used for Iran’s military-nuclear programs.

Reportedly, American hikers Sarah Shourd, Shane Bauer, and Josh Fattal were individuals the Iranians released in 2010 and 2011 as part of the dealings. In 2012, the United States began to reciprocate with its own release of Iranian prisoners Shahrzad Mir Gholikhan, Nosratollah Tajik, and Amir Hossein Seirafi.

According to the Times of Israel, Gholikhan was convicted on three counts of weapons trafficking. Tajik, a former Iranian ambassador to Jordan, was initially caught attempting to buy night-vision goggles from U.S. agents. He was later released after the U.S. decided not to follow up an extradition request it submitted to the British. In January of 2013 Seirafi was released; he was arrested in Frankfurt and convicted in the U.S. of attempting to purchase specialized vacuum pumps that could be used in the Iranian nuclear program.

In the meantime, Americans Robert Levinson, Amir Hekmati, and Saeed Abedini are currently imprisoned in Iran. U.S. State Department spokesman Jen Psaki told reporters on Tuesday, “The P5+1 talks focused exclusively on nuclear issues, but we have raised–repeatedly raised–his case and the cases of other detained American citizens including Amir Hekmati and Saeed Abedini in our bilateral discussions with Iran, including President Obama’s phone call with President Rouhani in September, so as recently as then, and we will continue to do so.”