Cyclic alternating pattern

Key points • Expressed by the physiological phasic events of NREM sleep, including arousals, cyclic alternating pattern represents the most complex arrangement of sleep microstructure. • Cyclic alternating pattern is organized in sequences organized in successive cycles. Each cyclic alternating pattern cycle is composed of a phase A (phasic events) and a phase B (background rhythm). • Cyclic alternating pattern involves not only cerebral activities during sleep, but paces, and is reciprocally influenced by ongoing autonomic and motor functions, with activation during phase A and deactivation during phase B. • The interaction between cyclic alternating pattern, neurovegetative fluctuations, and motor events determines the pathophysiology of several sleep disorders and the effect of medication and continuous positive airway pressure (CPAP) treatment. • Recent studies indicate the possibility of scoring cyclic alternating pattern automatically, opening new perspectives for a wider exploitation of this fundamental mechanism of the sleeping brain.