A small medical device placed on a patient's forehead to stimulate neural activity in the brain, used by Starfleet doctors to revive or stabilise people close to death.
The cortical stimulator delivers controlled pulses to the brain, usually as an emergency measure when a patient's neural activity is failing. It is among the most often seen instruments in Starfleet sickbays.
In The Next Generation, Beverly Crusher uses it in her vain attempt to save Tasha Yar in Skin of Evil, on Picard while he is linked to the Kataan probe in The Inner Light, and to bring Deanna Troi back from induced death in Man of the People.
Voyager's Doctor relies on it too, treating the comatose Chakotay in Cathexis and trying to revive Janeway in Coda. Julian Bashir uses one on Quark in the Deep Space Nine episode Necessary Evil, and Phlox directs its use in the Enterprise episode Observer Effect.