Section: Application Domains

General anaesthesia

During general anaesthesia, the EEG on the scalp changes characteristically: increasing the anaesthetic drug concentration the amplitudes of fast EEG-oscillations in the $\alpha$-band ($\sim 8-12$Hz) in frontal electrodes decrease and the amplitudes of slow oscillations in the $\delta -$band ($2-8$Hz) increase. This characteristic change in the power is the basis of today's EEG-monitors that assist the anaesthesist in the control of the anaesthesia depths of patients during surgery. However, the conventional monitors detect a large variability between the patients and are not able to detect the real depth of anaesthesia. Moreover, a certain number of patients re-gain consciousness during surgery (about $1-2$ out of 1000) and suffer from diverse after-effects, such as nausea or long-lasting cognitive impairments (from days to weeks). Since surgery under general anaesthesia is part of a hospital's everyday practice, a large number of patients suffer from these events everyday. One reason for the occurrence of these disadvantageous effects in hospital practice is the dramatic lack of understanding on what is going on in the brain during general anaesthesia leading to sometimes poorly controllable situations of patients. Consequently, to improve the situation of patients and to develop improved anaesthetic procedures or drugs, it is necessary to perform research in order to learn more about the neural processes in the brain.

The EEG originates from coherent neural activity of populations in the cortex. Hence to understand better the characteristic power changes in EEG during anaesthesia, it is necessary to study neural population dynamics subject to the concentration of anaesthetic drugs and their action on receptors on the single neuron level. We develop computational models which are constrained by the signal features extracted from experimental EEG and behavior. This methodology will reveal new knowledge on the neural origin of behavioral features, such as the loss of consciousness or the un-controlled gain of consciousness during surgery.