As New Scientist reports, researchers at George Washington University were using deep brain electrodes to monitor brain signals and try to pinpoint the area of a patient's brain that was causing her seizures. One of the electrodes was placed on the claustrum, a thin sheet of neurons running between major structures of the brain—and a region that's never been studied with deep brain electrodes before.
Unexpectedly, when the researchers sent high frequency electrical signals to the claustrum, the patient lost consciousness: unlike a seizure, where a person's activity immediately stops, the patient seemed to "slow down," speaking more quietly and moving more slowly until she was silent and still, unresponsive to voice or visual stimulation. She was, by definition, unconscious, regaining full consciousness with no memory of the event as soon as the electrical stimulation was turned off.
The discovery has huge potential implications for patients with epilepsy or in semi-conscious states, but this is a very early stage: so far, this on/off switch has only been tested in one patient. But pinpointing where consciousness is located in the brain will be crucial to deeper understanding of how the brain works, as researcher Christof Koch told New Scientist:
Maybe someday, we'll fall asleep by flipping the OFF switch located deep within our brains. More here.