Mohamad Koubeissi and team may have discovered the “on-off switch” for consciousness in the human brain.
A George Washington University researcher has begun to unlock the mystery of human consciousness.
The topic has always intrigued Mohamad Koubeissi, an associate professor of neurology and director of the Epilepsy Center at the School of Medicine and Health Sciences. While Dr. Koubeissi has been able to make patients’ limbs jerk and alter speech by electrically stimulating regions of the brain, consciousness—the state of being able to respond to stimuli and recall events—is much more complex.
“Consciousness has to do with widely distributed networks interacting with one another,” he said. “I was surprised to see that there was one region of the brain that, through electrical stimulation, could result in this global alteration of consciousness—with many spheres of cognition being paralyzed in just one moment.”
That is what Dr. Koubeissi and a team of researchers discovered while mapping the brain of a 54-year-old patient with severe epilepsy.
To try and identify the origins of her seizures, researchers placed deep electrodes in different areas of her brain, which they then stimulated with electrical charges in order to map her brain function. As the woman was reading a text, the researchers stimulated a region near the left claustrum—a thin, irregular sheet of neurons attached underneath the neocortex on either side of the brain.
The woman immediately stopped reading, stopped moving and stared blankly at the researchers as her breathing slowed. When stimulation stopped, she resumed consciousness with no memory of the incident.
“The conclusion is that this one specific spot may be heavily connected with all of the widely distributed networks that serve consciousness,” Dr. Koubeissi said.
In order to better characterize the phenomenon that he had observed, Dr. Koubeissi asked the woman to repeat and recall a series of three words. After the patient successfully repeated the first two words in her conscious state, Dr. Koubeissi stimulated the electrode near her claustrum and said the third word. He then turned the stimulator off and asked her to repeat what he had said. She repeated the first two words correctly but was not aware that he had spoken any third word.
The results of the anecdotal study appeared in the journal Epilepsy and Behavior.
Consciousness, according to Dr. Koubeissi, is difficult to define. While someone who is awake and talking would clearly be conscious, and someone in a coma would be considered unconscious, there is a whole spectrum of consciousness between these two extremes, he said. What is interesting about Dr. Koubessi’s particular discovery is that the woman remained upright and awake when the brain region was stimulated, while her cognition seemed to simultaneously turn off.
Though the phenomenon has yet to be replicated in other patients, Dr. Koubessi believes his finding could have significant clinical implications. For instance, stimulating this area of the brain could potentially improve the consciousness of coma patients or decrease the disruption of consciousness that accompanies epileptic seizures.
Beyond that, Dr. Koubeissi notes, it has been hypothesized that the role of the claustrum, based on its connectivity with other brain regions, may be to bind different sensory inputs together into what humans perceive as a single experience. For example, when holding a flower, most people note its color, its smell and its shape as a single transitory experience. For people with schizophrenia, though, there is a clear separation between thoughts, actions, emotions and perception.
“When there is such a separation, it may result from dysfunction in this particular region of the brain,” Dr. Koubeissi said. “Our discovery promises to shed light on such disorders.”