A thought record was an information storage system used by the Talosians to hold memories, which could then be accessed mentally for the purpose of living and reliving them. The Talosians had stored the lifes from members of several species from their part of the galaxy. Vina told Captain Pike in 2254, that, after they were driven underground by a massive war which devastated the surface of their planet, the Talosians became addicted to this practice, to the point where they even forgot how to maintain the machines left over by their ancestors. (TOS: "The Cage" )