Entering anesthesia, the mind seems to shut down abruptly and then later re-emerge from the blackness with equal swiftness. A new theoretical model suggests that these changes may result from a sudden, global change in the ability of the network of neurons to transmit information. The model can reproduce the changes in electrical activity (“brain waves”) seen with anesthetized patients. The researchers say that their theory could provide a simple foundation for understanding how the brain acquires its conscious cognitive functions.

Researchers don't understand how the activity of individual, interlinked neurons leads to the overall effect of anesthesia. Yan Xu and colleagues at the University of Pittsburgh School of Medicine wondered whether the loss of consciousness might be related to a reduced ability of sensory information to find its way through the brain’s neural network. This information must be transmitted from a region called the thalamus, which regulates consciousness and alertness, to the cortex, where “higher” cognitive functions process the information into a picture of the world.

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