Hal Blumenfeld is a professor of neurology, neurobiology and neurosurgery at the Yale School of Medicine. In July, Blumenfeld published an editorial entitled “A master switch for consciousness?” in the journal Epilepsy & Behavior. Previous research has established that the thalamus, a region of the brain responsible for coordinating higher cognitive actions, is crucial for consciousness. Now, Blumenfeld writes about research suggesting that a second region, including the insula and claustrum, may also play a role. The News talked with Blumenfeld to discussed the finding and its potential implications.

Q. What defines consciousness?\

A. Consciousness is a collection of activities. It’s basically the level of arousal — how awake you are, how attentive you are and how aware you are of yourself and of the world around you.

Q. Can you explain how researchers attempt to measure as abstract a concept as consciousness?

A. You can measure that by testing whether someone can do basic responses to questions and commands, which tells you how alert someone is. You can test someone’s attention by seeing if they can respond to specific things in their world as opposed to others, and you can test awareness by asking people to describe experiences they’ve had after they’ve occurred.

Q.You mentioned that the findings in your editorial might reveal a second master switch of consciousness. Can you explain how the first master switch works?

A. The first master switch is in the deep parts of the brain — in the brainstem, in the thalamus, so that’s what controls our sleep and wake cycles. If someone has a stroke or brain damage in those parts of the brain you go into a coma, so those are very well-known and understood areas. This new area that they stimulated electrically in this one patient produced unconsciousness, and it’s in the claustrum and the insula. The question is [whether] stimulation of that area also [is] a switch of consciousness separately, or is it just that by stimulating that area, you’re somehow having a remote or long-range effect on the first switch in the brainstem and in the thalamus and turning it off? You know that can happen because, for example, when people have seizures in the temporal lobe, which is not in the brainstem or the thalamus, that can switch off the brainstem and thalamus and cause loss of consciousness. Even though the seizure itself doesn’t come from that area, it can throw that master switch. It’s not clear if that second area does the same thing or not. It’s possible that it’s actually truly a new separate and independent master switch.

Q. How might temporal lobe seizures trigger the first switch?

A. The work from our lab shows that temporal lobe seizures do cause loss of consciousness that cause people to stare and not respond. Usually, a problem in a small region of the brain is expected to disrupt that part of the brain. For example, it might cause a problem with memory or emotions, but that’s not what happens. In temporal seizures people turn into what looks like a sleepwalking state, where they can’t respond at all: it’s just staring and having some chewing movements, or rubbing their shirt a little bit. It’s a mystery — why does that happen? We found by doing studies in patients with temporal epilepsy through brain imaging, and also by doing some neurology investigation in animal models, that what happens is the temporal lobe seizure invades the deep parts of the brain and by doing that, it turns off the master switch in the brainstem and thalamus, and that causes the rest of the brain to get shut off and go into a deep sleep-like state, which causes loss of consciousness.

Q. You did write that the possible second master switch needs to be confirmed in further patients, and its mechanisms further explored. What might be some of the challenges faced in furthering this research?

A. The biggest challenge is that not every patient with epilepsy happens to have an electrode in that spot. We only put electrodes there when people need it for clinical reasons. If we could do brain imaging, that would be ideal, [but] that’s very challenging to do with the electrodes in place. The problem right now is that the study is only limited to the electrodes where we happen to be able to record during the stimulation. It’s just a limited sample of the brain, but if we could actually take a picture of the whole brain while this stimulus is going on we could really get a much better understanding of whether this is throwing the first master switch, or whether it’s operating independently, or whether it’s affecting one side of the brain or both sides of the brain. A lot of those questions we don’t have answers to could really be answered with functional brain imaging approaches.

Q. What are the practical implications of this finding of a potential second master switch?

A. Understanding consciousness is very important because when people have problems with consciousness such as epilepsy, that’s when people lose control of their car if they’re driving, that’s when people lose the ability to concentrate in school or in work, or injure themselves, and it can even be fatal. Also, understanding consciousness is critical not just for transient things like seizures, but also for disorders like head injury, or stroke, or Alzheimer’s disease. [In these], consciousness eventually becomes severely impaired, so coming up with a better understanding of the brain networks that turn off consciousness can teach us ways to turn consciousness back on and prevent these problems for people, for people to have better quality of life.