Neural processor

From Memory Alpha, the free Star Trek reference

A neural processor is a device implanted in every Borg drone containing information it has received from the Collective.

When the Federation starship USS Enterprise-E traveled to the year 2063, Captain Jean-Luc Picard removed one such neural processor from the body of Ensign Lynch after the crewman was assimilated by a Borg boarding party. The captain was able to remove the technology, located in the abdomen, by shooting Lynch with a projectile weapon called a Tommy gun. Picard then attached the processor to a standard Mark X tricorder on which he was able to decode the information and discover the Borg's plan to build an interplexing beacon directly on the navigational deflector of the Enterprise. (Star Trek: First Contact)