The cerebral circulation during sleep: regulation mechanisms and functional implications.

Cerebral blood flow measurements during sleep are reviewed and discussed in relation to the different techniques utilized (Positron Emission Tomography, functional Magnetic Resonance Imaging, Flowmeters, Radioactive MicroIspheres, Brain Temperature Recordings, Spectrophotometry) since these methodological approaches aim at diverse features of circulation changes in the spatial or temporal domain. The regulation of cerebral circulation during sleep reveals no specific state-dependent features, flow-activity coupling being the prevailing mechanism, with O(2) as the primary candidate for the metabolic side of the link. On a general level, the latest data on brain circulation are compatible with the classical hypothesis of a "restorative" function of sleep processes. 2002 Harcourt Publishers Ltd