Regional differences of the human sleep electroencephalogram in response to selective slow-wave sleep deprivation.

The purpose of this study was to assess the topographic changes in sleep recuperative processes in response to selective slow-wave sleep (SWS) deprivation. SWS was suppressed on two consecutive nights by means of acoustic stimulation. The electroencephalogram (EEG) power of baseline, deprivation and recovery nights was analysed in 1 Hz bins. During the SWS deprivation nights, large decreases of EEG power were found at frontopolar, central and parietal derivations encompassing the delta, theta and alpha range, while only slow delta (0.5-2 Hz) was affected at the frontal derivation. Recovery sleep was characterized by a generalized increase of power during non-REM sleep encompassing the delta, theta and alpha bands, with a clear antero-posterior gradient. The coherent behaviour of different EEG bands with traditionally different electrophysiological meanings during non-REM sleep suggests that, in light of the recent advances in sleep neurophysiology, a re-examination of the functional role of EEG rhythms during sleep is needed. The 'resistance' to selective SWS deprivation of the frontal area, together with its larger increase of EEG power during recovery, may be interpreted as a sign of a greater sleep need of the frontal cortical areas, confirming that some aspects of the regulatory processes of human sleep are local in nature and may show use-dependent characteristics.