SCORING TRANSITIONS TO REM-SLEEP IN RATS BASED ON THE EEG PHENOMENA OF PRE-REM SLEEP - AN IMPROVED ANALYSIS OF SLEEP STRUCTURE

Algorithms for scoring sleep/waking states and transitions to REM slee p (NRTs) in rats are presented and validated. Both algorithms are base d on electroencephalographic (EEG) power in delta (0.5-4.0 Hz), theta (6-9 Hz) and sigma (10-14 Hz) frequency bands, and electromyogram (EMG ) intensity. Waking is scored when EMG intensity is high or (sigma pow er)(theta power) is low. Nonrapid eye movement (NREM) sleep is scored in nonwaking epochs having high (delta power)/(theta power). Rapid ey e movement (REM) sleep is scored in nonwaking epochs having low (delta power)/(theta power). NRTs are identified by the EEG phenomena of the pre-REM sleep phase of NREM sleep. Algorithms are validated by compar ison with records scored independently by two investigators based on v isual examination of EEGs and EMGs. The sleep/waking-state scoring alg orithm produces greater than 90% agreement with visual scoring. The NR T-scoring algorithm produces 88-92% agreement with visual scoring. Sco ring NRTs based on the phenomena of the pre-REM sleep phase of NREM sl eep, instead of relying solely on REM sleep expression for identificat ion of REM sleep onset, reveals a significant population of brief REM sleep episodes that are ignored by most sleep cycle analyses and allow s independent quantification of REM sleep timing and maintenance.