In 2368, a Borg sphere crashed on the planet's surface. Two of Nine, Three of Nine, Four of Nine, and Seven of Nine were the only survivors. Severed from the Borg Collective, the individual personalities of four drones began to re-surface. Three of the drones attempted to escape the Collective, destroying the beacon they were using to signal the Borg.
However, Seven of Nine's memories before her assimilation were those of a girl, and she became frightened by the prospect of being abandoned. Thus, she forced the others to repair the beacon by injecting nanoprobes that created new interlink nodes within their parietal lobes, establishing a neural link between the three of them. They were subsequently rescued and re-assimilated, but the neural link remained even after the three drones were later freed from the Collective. (VOY: "Survival Instinct")