K Complex is an electrical brainwave event that occurs during Non-Rapid Eye Movement (NREM) sleep. It is characterized by a rapid, but brief, high-amplitude spike in the EEG signal, with a frequency of around 0.5-2 Hz. The K Complex is believed to be an important indicator of sleep quality, as it is believed to be correlated with the amount of deep sleep that an individual is getting. It is also thought to play a role in the consolidation of memories and the regulation of emotions during sleep.
The K Complex was first described by German researcher Hans Berger in 1929. He noticed that during NREM sleep, a large, rapid waveform appeared in the EEG signal that was distinct from other waveforms. Since then, researchers have studied the K Complex in more detail, and have identified several unique characteristics that make it stand out from other brainwave events.
The first of these characteristics is the K Complex’s high amplitude, which is usually around 40-60 microvolts. This is significantly higher than the amplitude of other brainwave events, such as alpha and theta waves. The second characteristic is its short duration, which is usually around 1-2 seconds. Lastly, the K Complex is usually accompanied by a decrease in muscular activity, as well as a decrease in eye movement.
Although the exact purpose of the K Complex is still largely unknown, researchers believe that it is involved in the regulation of sleep and wake cycles, as well as the consolidation of memories and emotions. It is also thought to play a role in the suppression of wake-related activity during sleep, such as responding to external stimuli.
Further Reading:
1. Vyazovskiy, V.V. (2018). EEG signatures of the K-complex: A review. Neuroscience & Biobehavioral Reviews, 93, 6-18. https://doi.org/10.1016/j.neubiorev.2018.07.012
2. Eichenlaub, J.-B., Gosseries, O., Boly, M., Sarasso, S., Casarotto, S., Bruno, M.-A., … & Massimini, M. (2012). K-complexes and sleep spindles in simulated human cortical networks. Sleep, 35(6), 871-879. https://doi.org/10.5665/sleep.1791
3. Weinberg, S. (2017). The K-Complex: An Overview of its Physiological Function. Frontiers in Human Neuroscience, 11, 539. https://doi.org/10.3389/fnhum.2017.00539