<p>K complexes usually appear in Stage NREM&nbsp; of 2 sleep, and may also seen in Stages N3 sleep.. K-complexes consist of a broad vertex sharp waves accompanied by a run of sleep spindles.</p>
<p>The slow wave portion of the K complex can exceed 1000 milliseconds in duration. The amplitude may exceed 400 microvolts. K complexes appear spontaneously, or they can be elicited by an auditory stimulus (the “k” in K-complex stands for “Knock”).&nbsp;
    Knocking a counter, clapping, or tapping a pencil on a hard surface are good ways to elicit K complexes during EEG recordings. K complexes should be of equal voltage over both hemispheres.</p>
<p style="text-align: center;"><img src="@@PLUGINFILE@@/k-complex-sleeping-eeg.png" alt="Figure : K-Complex in a Sleeping EEG" width="570" height="683" class="img-responsive atto_image_button_text-bottom"><br></p>
<p style="text-align: center;">Figure : K-Complex in a Sleeping EEG<br></p><p style="text-align: center;"><br></p><p>Stage N3 sleep is characterized by an increase in higher voltage slow waves in the theta and delta range. Sleep spindles and K complexes may be present. As Stage N3 sleep progresses, the frequencies seen are slower and the number of sleep spindles decreases.&nbsp;&nbsp;</p><p>In <b>NREM 4</b>, delta increases, sleep spindles are no longer present, and the EEG consists of generalized, high voltage, irregularly shaped slow waves.&nbsp; Deeper sleep stages are seldom seen in routine EEG recordings unless the patient is sleep deprived and the recording period is lengthened.</p>