How the corticothalamic feedback affects the EEG

Authors: Meysam Hashemi Axel Hutt Jamie Sleigh

Publish Date: 2015/08/11

Volume: 39, Issue: 2, Pages: 155-179

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Abstract

Increasing concentrations of the anaesthetic agent propofol initially induces sedation before achieving full general anaesthesia During this state of anaesthesia the observed specific changes in electroencephalographic EEG rhythms comprise increased activity in the δ− 05−4 Hz and α− 8−13 Hz frequency bands over the frontal region but increased δ− and decreased α−activity over the occipital region It is known that the cortex the thalamus and the thalamocortical feedback loop contribute to some degree to the propofolinduced changes in the EEG power spectrum However the precise role of each structure to the dynamics of the EEG is unknown In this paper we apply a thalamocortical neuronal population model to reproduce the power spectrum changes in EEG during propofolinduced anaesthesia sedation The model reproduces the power spectrum features observed experimentally both in frontal and occipital electrodes Moreover a detailed analysis of the model indicates the importance of multiple resting states in brain activity The work suggests that the α−activity originates from the corticothalamic relay interaction whereas the emergence of δ−activity results from the full corticoreticularrelaycortical feedback loop with a prominent enforced thalamic reticularrelay interaction This model suggests an important role for synaptic GABAergic receptors at relay neurons and more generally for the thalamus in the generation of both the δ− and the α− EEG patterns that are seen during propofol anaesthesia sedationwhere HVe E equiv K RE S CVe E+frac K RSK ES Ve E Since all the resting states Vei a for a∈ERS can be written as an implicit function of Ve E the number of solutions of Ve E ie the number of roots of Eq 23 is identical to the number of resting states Robinson et al 1997 Robinson et al 1998 Robinson et al 2004and the diagonal matrix hat boldsymbol L partial /partial tp with the entries hat L 11 = hat L 33 = hat L 55 = hat L 77=hat L enu hat L 22 =hat L 44=hat L 66 = hat L inu p and

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