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How the Brain Loses and Regains Consciousness

Tuesday, March 5, 2013
Study reveals brain patterns produced by a general anesthesia drug; work could help doctors better monitor patients.
 
Since the mid-1800s, doctors have used drugs to induce general anesthesia in patients undergoing surgery. Despite their widespread use, little is known about how these drugs create such a profound loss of consciousness.

In a new study that tracked brain activity in human volunteers over a two-hour period as they lost and regained consciousness, researchers from MIT and Massachusetts General Hospital (MGH) have identified distinctive brain patterns associated with different stages of general anesthesia. The findings shed light on how one commonly used anesthesia drug exerts its effects, and could help doctors better monitor patients during surgery and prevent rare cases of patients waking up during operations.

Anesthesiologists now rely on a monitoring system that takes electroencephalogram (EEG) information and combines it into a single number between zero and 100. However, that index actually obscures the information that would be most useful, according to the authors of the new study, which appears in the Proceedings of the National Academy of Sciences the week of March 4. Read more...
 
 
  

 

This array of videos shows spectrographic data (representing brain wave frequencies) from each of 44 electrodes attached to the scalp of a healthy volunteer undergoing propofol anesthesia. The spectrograms are arranged according to their approximate position on the scalp, with the front of the head at the top of the screen, and the back of the head at the bottom of the screen. Activity moves from back to front with loss of consciousness (levels 1 to 5) and from back to front with return of consciousness (levels 6 to 8). Each video shows brain activity throughout a 140-minute period of the study. Video by Aylin Cimenser. Reproduced from PNAS with permission.