The K-complex: A 7-decade history

Human Sleep Research Program, SRI international and Department of Psychology, The University of Melbourne, Melbourne, Australia.
Sleep (Impact Factor: 4.59). 03/2005; 28(2):255-73.
Source: PubMed


The K-complex was first described by Loomis et al 67 years ago in a paper that was one of a series of seminal studies of sleep conducted in Loomis' private laboratory. The study of the K-complex was almost immediately taken up by many notable figures in early electroencephalography research, such as Robert Schwab, Mary Brazier, and W. Gray Walter. More than 200 papers have been published in the years since these early studies, including major reviews in 1956 by Roth et al and in 1985 by Peter Halász. More recently, K-complex study has been taken up by event-related potentials researchers such as Ken Campbell and animal neurophysiologists such as Florin Amzica and Mircea Steriade. The present paper provides a historical and thematically based review of the K-complex literature and attempts to integrate the various theoretical positions and neurophysiologic data. Specifically, K-complexes are discussed in terms of their relationship to other electroencephalographic phenomena, their relationship to autonomic activation, their role in the study of information processing during sleep, and what is understood of their underlying neurophysiology.

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    • "The expanding literature on the modification of various neurophysiological indices during various sleep stages constitutes a promising resource for ideas of features to test in the context of automatic sleep scoring. It is possible that higher performances could be achieved by exploring the discriminative power of further sleep specific neuronal phenomena: Quantifying the presence of K-complex waves (Colrain, 2005; Loomis et al., 1938), sleep spindles (Andrillon et al., 2011; Contreras and Steriade, 1996), bursts of high-frequency gamma oscillations (Ayoub et al., 2012; Dalal et al., 2010; Le Van Quyen et al., 2010; Valderrama et al., 2012; Worrell et al., 2012), monofractal and multifractal properties of the human sleep EEG (Weiss et al., 2009, 2011; Zorick and Mandelkern, 2013) and including them in the proposed DSVM method could potentially lead to an even better classification. The detection of some of these phenomena might be enhanced by recent methodological developments (Ahmed et al., 2009; Babadi et al., 2012; Chaibi et al., 2012, 2013, 2014; Jaleel et al., 2014; Nonclercq et al., 2013; O'Reilly and Nielsen, 2014a,b; Warby et al., 2014; Worrell et al., 2012). "
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    Full-text · Article · Jan 2015 · Journal of Neuroscience Methods
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    • "Nevertheless, submovements are not restricted to tracking tasks, and a natural rhythmicity is observed across diverse upper-limb behaviors (Kunesch et al., 1989) including self-paced isometric drawing (Massey et al., 1992) and finger tapping (Schö ner and Kelso, 1988). Moreover, low-frequency cortical oscillations have long been associated with slow-wave sleep, when large K complex potentials signifying transitions from down to up states of the cortex (Colrain, 2005; Cash et al., 2009) are accompanied by bursts of activity in the delta (1–4 Hz)-frequency range (Amzica and Steriade, 1997). At least two mechanisms contribute to these delta oscillations: intrinsic currents that cause bursting patterns in thalamic relay cells (Amzica et al., 1992; Destexhe and Sejnowski, 2003) and a second, purely cortical circuit (Amzica and Steriade, 1998; Carracedo et al., 2013). "
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    • "The N2 component of CAEP in children and adults is known to be enhanced by the first stages of non-rapid eye movement (NREM) sleep (equivalent of QS in preterm) [68]. Moreover, in children and adults, abrupt, and rare sensory stimuli whatever the modality are known to evoke vertex sharp waves and K-complexes in frontal-central areas in the first stages of NREM sleep [69], [70]. K-complexes are supposed to reflect inhibitory mechanisms associated with impaired transmission of sensory influx likely protecting QS from arousal [67]–[70]. "
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