Monitoring electrical activity using an auto-correlation technique

摘要

A method and apparatus for monitoring electrical activity, such as brainwaves, in an animal comprising detecting said activity to produce a corresponding output signal, combining the output signal with a random noise signal to produce a modified signal, and analysing the modified signal using an autocorrelation technique to detect the relative power density values at a plurality of different frequencies. The random noise signal may be a random number. The autocorrelation technique may involve the Yule-Walker method. The aim of the invention is to identify EEG signals in the 8 to 12 Hz frequency range as an indication of the depth of anaesthesia.