KKomplexe

K-complexes are distinctive EEG waveforms commonly observed during non-rapid eye movement sleep, particularly stage N2. They appear as a single, large biphasic wave: a sharp negative deflection followed by a slower positive component. Amplitude typically exceeds 75 microvolts, and they last about 0.5 to 2 seconds. K-complexes can occur spontaneously or be provoked by external stimuli such as loud noises or tactile input, and they are often associated with sleep spindles, another hallmark of N2 sleep.

The generation of K-complexes is believed to involve cortical networks with thalamic input, reflecting a transient shift toward a lighter, more arousable state followed by rapid re-synchronization back into deeper sleep. They are frequently interpreted as a protective mechanism that dampens processing of sensory stimuli to preserve sleep, while still allowing awakening if the stimulus is sufficiently strong.

In polysomnography, the presence of K-complexes helps define N2 sleep and contribute to sleep stage scoring. Their frequency and morphology can vary with age, prior sleep pressure, medications, and certain sleep-related conditions. K-complexes can be spontaneous or evoked by sensory events, and they show individual variability.

Abnormalities in K-complexes are not diagnostic on their own but may be observed in various neurological or sleep disorders or as a result of pharmacological effects. Overall, K-complexes are among the canonical features used to characterize human sleep architecture in clinical and research settings.