This page contains information regarding Star Trek: Discovery, and thus may contain spoilers.
The neural lock was an Emerald Chain device that could be used to control a person's actions. However, if used on an empath, it would inflict pain so excruciating that it would eventually cause death.
In 3189, an Emerald Chain boarding party used a neural lock to compel Commander Paul Stamets to operate the spore drive. Later, Osyraa had Zareh use a neural lock to torture Cleveland Booker, in an effort to force Commander Michael Burnham to tell them how to reach Theta Zeta. (DIS: "Su'Kal", "That Hope Is You, Part 2")