Cellular substrates and laminar profile of sleep K-complex

Neuroscience. 1998 Feb;82(3):671-86. doi: 10.1016/s0306-4522(97)00319-9.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Algorithms
  • Anesthesia, General
  • Animals
  • Brain / cytology*
  • Brain / physiology*
  • Cats
  • Electric Stimulation
  • Electrodes, Implanted
  • Electroencephalography*
  • Evoked Potentials / physiology
  • Sleep / physiology*