Neuroscientists link brain-wave pattern to energy consumption

Different brain states produce different waves of electrical activity, with the alert brain, relaxed brain and sleeping brain producing easily distinguishable electroencephalogram (EEG) patterns. These patterns change even more dramatically when the brain goes into certain deeply quiescent states during general anesthesia or a coma.

 
Emery Brown, an MIT professor of brain and cognitive sciences and health sciences and technology, left, and ShiNung Ching, a postdoc in Brown's lab. Photo: M. Scott Brauer

MIT and Harvard University researchers have now figured out how one such quiescent state, known as burst suppression, arises. The finding, reported in the online edition of the Proceedings of the National Academy of Sciences the week of 6 February, could help researchers better monitor other states in which burst suppression occurs. For example, it is also seen in the brains of heart attack victims who are cooled to prevent brain damage due to oxygen deprivation, and in the brains of patients deliberately placed into a medical coma to treat a traumatic brain injury or intractable seizures.

During burst suppression, the brain is quiet for up to several seconds at a time, punctuated by short bursts of activity. Emery Brown, an MIT professor of brain and cognitive sciences and health sciences and technology and an anesthesiologist at Massachusetts General Hospital, set out to study burst suppression in the anesthetised brain and other brain states in hopes of discovering a fundamental mechanism for how the pattern arises.

Such knowledge could help scientists figure out how much burst suppression is needed for optimal brain protection during induced hypothermia, when this state is created deliberately.

''You might be able to develop a much more principled way to guide therapy for using burst suppression in cases of medical coma,'' says Brown, senior author of the PNAS paper. ''The question is, how do you know that patients are sufficiently brain-protected? Should they have one burst every second? Or one every five seconds?''

Modelling electrical activity