Interlink node

An interlink node is a form of bionetic technology implanted within every Borg drone, which enables communication with other drones.

In 2368, after their Borg sphere crashed on Planet 1865-Alpha, Seven of Nine, fearful of being abandoned, injected three other drones who had survived with her with nanoprobes that created new organic interlink nodes in their left parietal lobes. This resulted a new neural link between them, which persisted even after the three were later freed from the Borg Collective. 

In 2375, the Devore detected Seven of Nine's interlink node during one of their inspections. 

In 2376, Lieutenant Commander Tuvok successfully "bridged" the minds of Captain Kathryn Janeway and former Borg drone Seven of Nine, using a Vulcan mind meld in lieu of an interlink node. This allowed Janeway to experience the virtual construct known as Unimatrix Zero, normally accessible only to Borg drones during regeneration.