Cross-Species Investigation on Resting State Electroencephalogram

Resting state electroencephalography (EEG) during eyes-closed and eyes-open conditions is widely used to evaluate brain states of healthy populations and brain dysfunctions in clinical conditions. Although several results have been obtained by measuring these brain activities in humans, it remains unclear whether the same results can be replicated in animals, i.e., whether the physiological properties revealed by these findings are phylogenetically conserved across species. In the present study, we describe a paradigm for recording resting state EEG activities during eyes-closed and eyes-open conditions from rats, and investigated the differences between eyes-closed and eyes-open conditions for humans and rats. We found that compared to the eyes-open condition, human EEG spectral amplitude in the eyes-closed condition was significantly higher at 8-12 Hz and 18-22 Hz in the occipital region, but significantly lower at 18-22 Hz and 30-100 Hz in the frontal region. In contrast, rat EEG spectral amplitude was significantly higher in the eyes-closed condition than in the eyes-open condition at 1-4 Hz, 8-12 Hz, and 13-17 Hz in the frontal-central region. In both species, the 1/f-like power spectrum scaling of resting state EEG activities was significantly higher in the eyes-closed condition than in the eyes-open condition at parietal-occipital and frontal regions. These results provided a neurophysiological basis for future translational studies from experimental animal findings to human psychophysiology, since the validity of such translation critically relies on a well-established experimental paradigm and a carefully-examined signal characteristic to bridge the gaps across different species.