Analysis of non-REM sleep staging with electroencephalography bispectral index

The present study provides results in an early sleep period for non-REM stage correlation with bispectral index (BIS) values. The purpose of the study was to assess the applicability of an objective procedure to monitor sleep. Nine healthy subjects (mean age: 25.0 +/- 4.4; 1 female) were recruited for the study without history of any neurological, psychiatric, or sleep-related disorders. Electroencephalography (EEG) signals from 30 electrodes referenced to linked earlobe electrodes, and electrooculography (EOG) and electromyography (EMG) activities were recorded. BIS recording was performed simultaneously with EEG recording. Because that the current study is related to non-REM sleep, corresponding to the first sleep cycle, approximately 90 min of data was processed both for BIS and EEG data pools. The sleep staging was done using traditional Rechtschaffen and Kales scoring (R&K) and BIS scores were acquired online. The BIS values corresponded well to sleep depth, decreasing in accordance with sleep stages. Overall BIS correlation with sleep scores in the non-REM was found to be r = 0.86 (Spearman analysis, n = 9, r(2) = 0.75). Accompanying the traditional scoring, BIS and BIS-like tools can be useful for information processing and for psychophysiological applications in neurology, psychiatry, and further studies on consciousness