K-complex

K-complexes have two proposed functions:[1] first, suppressing cortical arousal in response to stimuli that the sleeping brain evaluates not to signal danger, and second, aiding sleep-based memory consolidation.

[6] They are created by the occurrence in widespread cortical areas of outward dendritic currents from the middle (III) to the upper (I) layers of the cerebral cortex.

[8] This would be consistent with a function in suppressing cortical arousal in response to stimuli that the brain needs to initially process in regard to whether it is dangerous or not.

The activation thresholds of cortical synapses become lowered during wakefulness as they process information, making them more responsive, and so need to be adjusted back to preserve their signal-to-noise ratio.

[9] The down-state provided by K-complexes does this by reducing the strengths of synaptic connections that occur while an individual is awake.

[10] In individuals with idiopathic generalized epilepsy, K-complex induced synchronization can trigger spike-and-wave discharges.

[11] In autosomal dominant nocturnal frontal lobe epilepsy, K-complexes are almost invariably present at the start of seizures.