[The role of micro-arousals in the regulation of sleep]

This work give a short account about a three decades research of the sleep microstructure. The studies, executed by the Strassbourg, Budapest and Parma schools, paved the way of exploring the participation of micro-arousals in the sleep regulation. It was shown that micro-arousals, not leading to instant arousal but influencing the later course of sleep are weaved into the network of sleep. A certain class of micro-arousals differs from the traditional desyncronisation-type and in a paradox way result a rebound like mobilisation of sleep-like activity with deltas and K-complexes. The desynchronisation- and synchronisation-type micro-arousals show different distribution along the sleep cyclicity and may play different role in sleep regulation. On the basis of the studies dealing with micro-arousals we can assume that beside the traditional long time constant, brain stem driven tonic chemical regulation, an other phasic regulation, with shorter time constant, associated with the micro-arousals, also exists. This kind of phasic regulation makes sleep flexible and possible to adapt the actual sleep course to the inner and outer demands. An other important role of micro-arousals in pathological sleeps is to provide a gate for the different pathological events, pinpointing the key-points where these events could be expected in the sleep process.