Local origin of slow EEG waves during sleep.

Neuronal activity mediating EEG slow waves consists of synchronous alternation of intracellular active and silent states. Recent data demonstrate that each active state of a sleep slow wave originates in a particular cortical location and propagate to involve other cortical areas. Preferential sites of origin of these waves are: the frontal cortex in adult humans, the associative cortex in cats and the somatosensory cortex in mice. In the site of origin of these slow waves any neuron can initiate a particular cycle, however there are neuronal groups with high likelihood of triggering a particular cycle. In epileptic patients, these neurons are mostly located in superficial layers, but in healthy experimental animals, populations ofintrinsically bursting neurons with a high probability of triggering spontaneous active states have been found in deeper cortical layers.