Are corticothalamic ‘up’ states fragments of wakefulness?
Alain Destexhe, Stuart Hughes, Michelle Rudolph and Vincenzo Crunelli

Trends in Neurosciences 30: 334-342, 2007.

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The slow (<1 Hz) oscillation, with its alternating ‘up’ and ‘down’ states inindividual neurons, is a defining feature of the electroencephalogram (EEG) during slow-wave sleep (SWS). Although this oscillation is well preserved across mammalian species, its physiological role is unclear. Electrophysiological and computational evidence from the cortex and thalamus now indicates that slow-oscillation ‘up’ states and the ‘activated’ state of wakefulness are remarkably similar dynamic entities. This is consistent with behavioural experiments suggesting that slow-oscillation ‘up’ states provide a context for the replay, and possible consolidation, of previous experience. In this scenario, the T-type Ca2+ channel-dependent bursts of action potentials that initiate each ‘up’ state in thalamocortical (TC) neurons might function as triggers for synaptic and cellular plasticity in corticothalamic networks.