EB: We give volunteers anesthetic drugs over a controlled period of time. As they get more drug, they go deeper into anesthesia. We can see how the brain changes as this occurs using fMRI and EEG. [FMRI, or functional magnetic resonance imaging, measures changes in blood flow to specific parts of the brain and is very spatially precise. EEG, or electroencephalogram, measures the electrical activity of the brain and is very temporally precise.]

We know from previous studies the EEG patterns that correspond to different depths of anesthesia. By combining this with fMRI, we might be able to see something in the brain that gives an idea of the origin of those EEG patterns.

Up until relatively recently, doing combined EEG and fMRI was impossible. The MRI magnet produced large currents in the EEG wires that could potentially burn people. And the MR signal created wide signal distortions. But my colleagues at Mass General worked out a safe way to record brain activity in the magnet and developed signal-processing techniques that help minimize distortions.

TR: Is it difficult to study anesthesia in people?

EB: Most anesthesia drugs stop you from breathing: patients are put to sleep and then given a breathing tube. But because we want to study the transitions in anesthesia, including when a patient stops breathing, we study a special set of volunteers: people who have had tracheostomies, a surgical opening at the neck to aid breathing after cancer or injury. If these people stop breathing as they fall off to sleep, you can help them breathe.

TR: How do you see your research changing the practice of anesthesia?

EB: It will give us a way of tracking what the brain is doing under anesthesia. Let's say I completed my study and know what brain regions are shut down during different stages of anesthesia, and I know what EEG patterns those changes are associated with. We could put an EEG on the patient in the operating room and say, "I see pattern A, so I know brain region X is shut down, but not region Y, so maybe we shouldn't start the surgery yet."