General anaesthesia (GA) is a medical procedure which aims to achieve analgesia, amnesia, immobility and skeletal muscle relaxation. Although GA is commonly used in medical care for patients undergoing surgery, its precise underlying mechanisms and the molecular action of anaesthetic agents (AA) remain to be elucidated. A wide variety of drugs are used in modern anaesthetic practice and it has been observed that for many AAs, during the transition from consciousness to unconscious- ness, the electroencephalogram shows biphasic effects in amplitude: an initial increase of the spectral power followed by a decrease at higher concentrations. Moreover during the administration of propofol, specific changes in EEG rhythms can be observed. The aim of this work is the extended discussion of a recent model by Hindriks and van Putten [10] that reproduces specific changes in EEG rhythms by the study of a neu- ronal population model of a single thalamocortical module. We illustrate specific features of the model, such as the physiological assumptions, the derivation of the power spectral density and the impact of the propofol concentration and of the stationary state. We show that the propofol- induced modification of the stationary state plays an important role in the understanding of the observed EEG.
