Scientists have wondered for some time if a person could experience a state of unconsciousness without entering into a deep sleep. Now a new anecdotal study, published in the journal Epilepsy and Behavior, demonstrates it may be possible to turn someone's consciousness on and off like the switch of a light.
Researchers made the discovery after implanting electrodes in the brain of a 54-year-old woman with intractable epilepsy. They were looking to identify the site of the woman's seizures, using electrical stimulation on various regions of her brain including the claustrum, a thin layer of neurons attached to the neocortex center of the brain.
Stimulating this area of the brain appeared to disrupt normal consciousness. Once the electrodes were shut off, the woman returned to a normal state of consciousness and had no memory of what had just occurred. Though the woman was unresponsive while in this state, the brain stimulation caused only a minor change to her motor and language abilities. Additionally, stimulating the claustrum did not cause a seizure.
To confirm that the woman was experiencing a state of unconsciousness, and not simply losing her ability to speak or move, the researchers asked her to repeat a word or snap her fingers before they began to stimulate her brain. They theorized that if the stimulation was simply disrupting those functions, she would have stopped moving and speaking immediately. Instead the researchers noticed that her motor and speech abilities tapered off slowly.
"The claustrum could constitute a common gate to the 'external' and 'internal' awareness networks," the authors write in their study. "This could explain why the electrical stimulation of the claustrum, and the resulting alteration of its normal function, would cause an impairment of consciousness, including an absence of recollection of the external events and of internal/interoceptive experience." (Interoceptive refers to a stimulus in the body.)
More and more, scientists are employing the technique of brain stimulation to treat a number of neurological health conditions, including Parkinson's disease, Alzheimer's disease and dystonia, or involuntary movement disorders. The technique has also proved promising for people with depression.
The findings of this experiment are not only a first step to identifying the region linked to consciousness. The researchers also say that stimulating the area of the brain may help provide a new way to treat epilepsy and possibly also patients in a coma or with schizophrenia or other disorders.