What is the defining characteristic of K-complexes in EEG readings?

K-complexes are distinctive waveforms observed in electroencephalograms (EEGs) during sleep and are primarily characterized as unique responses to sensory stimuli. These waveforms arise typically in the context of non-REM sleep and often reflect the brain's mechanism for processing external stimuli while maintaining a state of sleep. They can occur in response to sounds or other environmental stimuli, helping to protect sleep by suppressing awareness of minor disturbances.

This characteristic of being associated with sensory stimuli signifies their role in sleep biology, especially in how the brain manages and integrates sensory information during rest. K-complexes may sometimes indicate that the sleeper is still responsive to the environment, which is an important aspect of sleep architecture.

In contrast, while K-complexes may appear during some stages of sleep that could be considered deeper, they are not exclusively indicative of deep sleep stages, nor do they signify neurological impairment. K-complexes serve a specific function regarding how sensory information is processed during sleep rather than reflecting any pathology or deeper cognitive processes.