Cellular substrates and laminar profile of sleep K-complex.
We describe the cellular mechanisms that underlie the generation of the K-complex, a major grapho-element of sleep electroencephalogram in humans. First we demonstrate the similarity between K-complexes recorded during natural sleep and under ketamine-xylazine anaesthesia in cats. Thereafter, we show by means of multi-site cellular and field potential recordings that K-complexes are rhythmic at frequencies of less than 1 Hz (mainly 0.5-0.9 Hz) and that they are synchronously distributed over the whole cortical surface as well as transferred to the thalamus. The surface K-complex reverses its polarity at a cortical depth of about 0.3 mm. At the cortical depth, the K-complex is made of a sharp and high-amplitude negative deflection that reflects cellular depolarization, often preceded by a smaller-amplitude, positive slow-wave reflecting cellular hyperpolarization. The sharp component of the K-complex may lead to a spindle sequence and/or to fast (mainly 20-50 Hz) oscillations. K-complexes appear spontaneously or triggered by cortical or thalamic stimulation, and they arise within cortical networks. We suggest that K-complexes, either in isolation or followed by a brief sequence of spindle waves, are the expression of the spontaneously occurring, cortically generated slow oscillation.
Amzica
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Laboratoire de Neurophysiologie, Faculté de Médecine, Université Laval, Quebec, Canada.
Steriade
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D000465:Algorithms; D000768:Anesthesia, General; D000818:Animals; D001921:Brain / Q000166:cytology* / Q000502:physiology*; D002415:Cats; D004558:Electric Stimulation; D004567:Electrodes, Implanted; D004569:Electroencephalography; D005071:Evoked Potentials / Q000502:physiology; D012890:Sleep / Q000502:physiology*