In 2367, while exploring a cavern on Alpha Onias III, Commander William T. Riker was rendered unconscious by gases. While unconscious, neural scanners scanned Commander William T. Riker's brain. The scanners used elements of Riker's reality and constructed a holodeck simulation with those elements interspersed throughout, so that it felt real to him. What Riker wanted, the scanners made possible.
In one of these simulations, the Alpha Onias expedition was an expedition to the planet Alpha Onias III by the USS Enterprise-D. The Enterprise was investigating a signal emanating from the planet's surface that had probed the Federation starship. An away team, led by Riker, and consisting of Geordi La Forge and Worf, was given the task of tracking down the signal. During the course of the expedition, Riker was infected by Altarian encephalitis. This virus did not affect La Forge or Worf. Despite this setback, the expedition was a success. On stardate 46048, Riker was commended by Captain Jean-Luc Picard for exceptional service with the citation reading, "Commander Riker's leadership skills and his scientific abilities were key factors in this mission." In 2283, this expedition was mentioned in Riker's service record that was on display in his quarters on the Enterprise-D. (TNG: "Future Imperfect", okudagram)