Does REM sleep contribute to sleep homeostasis?

An unanswered question on sleep regulation regards the role of REM sleep (REMS). Most studies on homeostatic aspects of sleep regulation have been focused on non-REM sleep (NREMS), while the role of REMS has been neglected. Since the evaluation of EEG changes induced by extended waking provides the most grounded approach to this issue, we studied a large sample of healthy subjects within a sleep deprivation protocol, considering a full-scalp topography. Methods: The sleep EEG of 40 subjects (age524.6 yrs) was recorded from 19 derivations in 3 nigths (adaptation, baseline - BSL-, recovery after 40 h of sustained wakefulness -REC-). EEG power was calculated across the 0.50–25 Hz range (resolution51 Hz), separately for REMS and NREMS. Statistical comparisons between REC versus BSL were calculated for 1-Hz power maps of NREMS and REMS, yielding a full-scalp topography of homeostatic changes in both states. Finally, the magnitude of changes in NREMS and in REMS was correlated. Results and Conclusions: NREMS: Power maps of BSL reveal stable patterns within different frequency ranges, and maxima and minima exhibited the typical features of power spectra in NREMS. The delta and alpha ranges exhibit a frontal midline predominance and minima over the temporal regions. In the theta band, the highest values are seen at the fronto-central midline areas, while sigma power shows centro-parietal maxima. The statistical maps of the REC versus BSL differences reveal topography-specific increases from 0.5 to 12 Hz and decreases from 13 to 16 Hz. REMS: Power maps of BSL also reveal that the 0.5–7 Hz range exhibits fronto-central midline maxima and minima over the temporal areas, while the highest values of the alpha band are seen at the parietal-occipital areas. The statistical maps of the REC versus BSL differences point to topography-specific increases from 0.5 to 7 Hz and decreases from 8 to 11 Hz. Hence, the 1–7 Hz range shows significant and topography-specific increases as a An unanswered question on sleep regulation regards the role of REM sleep (REMS). Most studies on homeostatic aspects of sleep regulation have been focused on non-REM sleep (NREMS), while the role of REMS has been neglected. Since the evaluation of EEG changes induced by extended waking provides the most grounded approach to this issue, we studied a large sample of healthy subjects within a sleep deprivation protocol, considering a full-scalp topography. Methods: The sleep EEG of 40 subjects (age524.6 yrs) was recorded from 19 derivations in 3 nigths (adaptation, baseline - BSL-, recovery after 40 h of sustained wakefulness -REC-). EEG power was calculated across the 0.50–25 Hz range (resolution51 Hz), separately for REMS and NREMS. Statistical comparisons between REC versus BSL were calculated for 1-Hz power maps of NREMS and REMS, yielding a full-scalp topography of homeostatic changes in both states. Finally, the magnitude of changes in NREMS and in REMS was correlated. Results and Conclusions: NREMS: Power maps of BSL reveal stable patterns within different frequency ranges, and maxima and minima exhibited the typical features of power spectra in NREMS. The delta and alpha ranges exhibit a frontal midline predominance and minima over the temporal regions. In the theta band, the highest values are seen at the fronto-central midline areas, while sigma power shows centro-parietal maxima. The statistical maps of the REC versus BSL differences reveal topography-specific increases from 0.5 to 12 Hz and decreases from 13 to 16 Hz. REMS: Power maps of BSL also reveal that the 0.5–7 Hz range exhibits fronto-central midline maxima and minima over the temporal areas, while the highest values of the alpha band are seen at the parietal-occipital areas. The statistical maps of the REC versus BSL differences point to topography-specific increases from 0.5 to 7 Hz and decreases from 8 to 11 Hz. Hence, the 1–7 Hz range shows significant and topography-specific increases as a