Cortical inhibitor

A cortical inhibitor was a device used to control theta wave activity in the brain.

In 2373, The Doctor convinced Lieutenant B'Elanna Torres to wear a cortical inhibitor to stop the dreams she was having about a portion of Enaran history. 

In 2375, The Doctor used cortical inhibitors to stimulate neurotransmitters in Seven of Nine's brain, to suppress the emergence of dormant neural patterns of previously assimilated individuals. The patterns were emerging due to the neural interlink frequency of a vinculum that had been infected with Species 6339's synthetic pathogen, which eventually overwhelmed the inhibitors. 

Later that year, The Doctor used a cortical stimulator to elevate neurotransmitter levels in B'Elanna Torres' brain in an unsuccessful attempt to counteract a neurogenic field being produced by the telepathic pitcher plant. 

Borg drones were equipped with cortical inhibitors that played a role in suppressing their individuality. In 2376, The Doctor modified Axum's nanovirus to nullify the cortical inhibitors of the drones inside Unimatrix Zero so that they could retain their memories outside of regeneration.