[Topographical distribution of EEG activity induced by anesthetic agents]

Having noticed in a wide series of subjects submitted to prolonged anaesthesia that the EEG activities induced by anaesthetic products exhibited transverse topographic distributions (preferentially medial or preferentially lateral) which varied in relation to the product utilised, the authors have verified, in a more limited series of 25 subjects, that benzodiazepines, the targets of which are situated within the axial structures of the CNS, are responsible for EEG modifications which show a maximal amplitude on the parasagittal medial area of the scalp, while propanidide, which mainly affects the cortex of the convexity (i.e. the superior level of the lateral structures of the CNS), induces activities which show a maximal amplitude on the lateral areas of the scalp. The EEG modifications induced by thiopental and fentanyl are also lateralized but more diffuse. These data must be verified by a more precise study of a larger series, taking into account the dose and the speed of injection of the anaesthetic agent.