Cortical Node
The Cortical Node is a Borg implant that sits in a socket above the right eyebrow as a part of a Borg Drone's cortical array. (VOY: "Human Error") It is the single most important component a Borg drone possesses as it serves in controlling all of the drone's other implants. If the cortical node malfunctions, the implants will fail and be rejected, killing the drone. Its technology is too advanced to attempt to repair; in the Borg Collective, if a drone's cortical node malfunctions, the node is replaced entirely. If a drone has been dead for more than an unspecified period, its cortical node becomes inactive and therefore cannot be used to replace a malfunctioning node. (VOY: "Imperfection")
Built into every cortical node is a fail-safe mechanism designed to shut down the higher brain functions when the drone achieves a certain amount of emotional stimulation, in order to deactivate drones who start to regain their emotions. This is to prevent the drone's mind from regaining a sense of individuality, breaking the Collective's control over it. (VOY: "Human Error")
