Several complexity measures, especially approximate entropy (ApEn) and a new defined complexity measure , of EEG signals or the ones of the mutual information transmission between different channels of EEGs were calculated to distinguish different consciousness levels for different brain functional states. All of the measures decreased with the following order of brain states: rest with eyes open, eyes closed, light sleep and deep sleep. They decreased during epileptic seizures. On the contrary, the averaged mutual information between different channels increased significantly during the epileptic seizure; there is no significant difference among the averaged mutual information for the subject resting with eyes open, closed, being in light sleep and in deep sleep. Thus, the former indexes seem to be promising candidates to characterize different consciousness levels, while the latter seems not.
['Fanji Gu', 'Xin Meng', 'Enhua Shen', 'Zhijie Cai']
CAN WE MEASURE CONSCIOUSNESS WITH EEG COMPLEXITIES