The Raven River experiments were flashforward experiments designed by Dyson Frost, who also participated in them and was one of the few survivors. ("The Garden of Forking Paths")

Six months before the Global Blackout, Lucas Hellinger mentioned the experiments while introducing Alda Hertzog to Frost. ("The Garden of Forking Paths")

While Demetri Noh was held captive, Frost told him that the experiments began to be conducted in the 1980s at a place called Raven River, and that the participants had thousands of flashforwards. ("The Garden of Forking Paths")

Gabriel McDow mentioned to Olivia Benford and Shelly Vreede that he and the homeless man were also participants in the Raven River experiments. ("The Garden of Forking Paths")

Vreede figures out that the Raven River experiments were conducted at the Raven River Hospital. When Olivia and Vreede go there to investigate, they encounter McDow again, who reveals to them the nature of the Raven River experiments. ("Goodbye Yellow Brick Road")

When shown photographs of Nhadra Udaya and Kent Nelson by the FBI, Gabriel McDow told the FBI that they were both part of the Raven River experiments. ("The Negotiation")