The Neuroscience of Anesthesia

Anesthesia drugs have been used in the US for 170 years without being well understood. Emery Brown has changed that. The Edward Hood Taplin Professor of Medical Engineering and Computational Neuroscience at MIT, Brown is also director of the Harvard-MIT Health Sciences and Technology Program, associate director of the Institute for Medical Engineering and Science (IMES), and an investigator at MIT’s Picower Center for Learning and Memory.

Anesthesia drugs create long, large brain waves that are readily visible in the electroencephalogram (EEG). Since 1937, it has been possible to monitor an anesthetized brain using EEG. Brown has shown that these highly structured brain waves are produced by the anesthesia drugs binding at specific molecular targets and specific brain circuits and disrupting communication among different brain regions. The brain wave patterns change systematically with the type of anesthetic and the age of the patient.

Brown, who is also an anesthesiologist at Massachusetts General Hospital, now understands those EEG readouts so well that he has put them to work in the operating room. Brown and his collaborators have developed computer programs that transform the EEG into a spectrogram, a colorful visual display that provides an at-a-glance picture of the patient’s brain state.

Relying on the information from this display, Brown has found that, particularly among the elderly, he can cut the dose of anesthetic used by 50% to 75% in some cases. Real-time monitoring also opens the possibility for automatic control of anesthesia—a compelling need in the treatment of patients who must remain in medically induced comas for days, or even months.

Brown’s monitoring technology has made it clear that the most common anesthesia drugs used today act in different ways on different brain regions to control pain and consciousness. This insight opens the door for these drugs to be used in a more informed way: “We’re taking a step back and saying, now that we understand how these drugs work, how can we devise new strategies for anesthesia?”