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The slow oscillation: a sleep master-clock for co-ordination of neuronal ensembles

Vincenzo Crunelli
School of Biosciences, Cardiff University, Cardiff

The slow (<1 Hz) sleep oscillation is the defining EEG feature of slow wave sleep. Although thalamic and cortical neurons can produce the basic waveform of this rhythm independently from each other, the full manifestation of the slow sleep oscillation and it UP and DOWN states results from the dynamic interaction of three independent oscillators: a mainly synaptically-based cortical oscillator and two intrinsic thalamic oscillators which are located in the thalamocortical neurons and the reticular thalamic neurons. The presence of the slow oscillation and the similarities of its basic properties across all species where it has so far been investigated (i.e. mouse, rat, guinea pig, ferret, cat, man) emphasize the fundamental significance of this brain wave for survival, and potentially for learning. Moreover, this vital emergent property of corticothalamic networks has many biochemical, electrical and computational properties that are highly suited for synchronizing local and distant neuronal assemblies, and for allowing intrinsic and network plasticity.