Algorithmic complexity as an index of cortical function in awake and pentobarbital-anesthetized rats

This study introduces algorithmic complexity to measure characteristics of brain functions. The EEG of the rat was recorded with implanted electrodes. The normalized complexity value was relatively independent of data length, and it showed a simpler and easier calculation characteristic than other n on-linear indexes. The complexity index revealed significant differences am ong awake, asleep, and anesthetized states. It may be useful in tracking sh ort-term and long-term changes in brain functions, such as anesthetized dep th, drug effects, or sleep-wakefulness. (C) 1999 Elsevier Science B.V. All rights reserved.