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.

31 Reads
  • Source
    • "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). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Background: Sleep staging is a critical step in a range of electrophysiological signal processing pipelines used in clinical routine as well as in sleep research. Although the results currently achievable with automatic sleep staging methods are promising, there is need for improvement, especially given the time-consuming and tedious nature of visual sleep scoring. New method: Here we propose a sleep staging framework that consists of a multi-class support vector machine (SVM) classification based on a decision tree approach. The performance of the method was evaluated using polysomnographic data from 15 subjects (electroencephalogram (EEG), electrooculogram (EOG) and electromyogram (EMG) recordings). The decision tree, or dendrogram, was obtained using a hierarchical clustering technique and a wide range of time and frequency-domain features were extracted. Feature selection was carried out using forward sequential selection and classification was evaluated using k-fold cross-validation. Results: The dendrogram-based SVM (DSVM) achieved mean specificity, sensitivity and overall accuracy of 0.92, 0.74 and 0.88 respectively, compared to expert visual scoring. Restricting DSVM classification to data where both experts' scoring was consistent (76.73% of the data) led to a mean specificity, sensitivity and overall accuracy of 0.94, 0.82 and 0.92 respectively. Comparison with existing methods: The DSVM framework outperforms classification with more standard multi-class "one-against-all" SVM and linear-discriminant analysis. Conclusion: The promising results of the proposed methodology suggest that it may be a valuable alternative to existing automatic methods and that it could accelerate visual scoring by providing a robust starting hypnogram that can be further fine-tuned by expert inspection.
    Journal of Neuroscience Methods 01/2015; 250. DOI:10.1016/j.jneumeth.2015.01.022 · 2.05 Impact Factor
  • Source
    • "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). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Upper-limb movements are often composed of regular submovements, and neural correlates of submovement frequencies between 1 and 4 Hz have been found in the motor cortex. The temporal profile of movements is usually assumed to be determined by extrinsic factors such as limb biomechanics and feedback delays, but another possibility is that an intrinsic rhythmicity contributes to low frequencies in behavior. We used multielectrode recordings in monkeys performing an isometric movement task to reveal cyclic activity in primary motor cortex locked to submovements, and a distinct oscillation in premotor cortex. During ketamine sedation and natural sleep, cortical activity traversed similar cycles and became synchronized across areas. Because the same cortical dynamics are coupled to submovements and also observed in the absence of behavior, we conclude that the motor networks controlling the upper limb exhibit an intrinsic periodicity at submovement frequencies that is reflected in the speed profile of movements.
    Neuron 08/2014; 83(5). DOI:10.1016/j.neuron.2014.07.022 · 15.05 Impact Factor
  • Source
    • "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]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: In the premature infant, somatosensory and visual stimuli trigger an immature electroencephalographic (EEG) pattern, "delta-brushes," in the corresponding sensory cortical areas. Whether auditory stimuli evoke delta-brushes in the premature auditory cortex has not been reported. Here, responses to auditory stimuli were studied in 46 premature infants without neurologic risk aged 31 to 38 postmenstrual weeks (PMW) during routine EEG recording. Stimuli consisted of either low-volume technogenic "clicks" near the background noise level of the neonatal care unit, or a human voice at conversational sound level. Stimuli were administrated pseudo-randomly during quiet and active sleep. In another protocol, the cortical response to a composite stimulus ("click" and voice) was manually triggered during EEG hypoactive periods of quiet sleep. Cortical responses were analyzed by event detection, power frequency analysis and stimulus locked averaging. Before 34 PMW, both voice and "click" stimuli evoked cortical responses with similar frequency-power topographic characteristics, namely a temporal negative slow-wave and rapid oscillations similar to spontaneous delta-brushes. Responses to composite stimuli also showed a maximal frequency-power increase in temporal areas before 35 PMW. From 34 PMW the topography of responses in quiet sleep was different for "click" and voice stimuli: responses to "clicks" became diffuse but responses to voice remained limited to temporal areas. After the age of 35 PMW auditory evoked delta-brushes progressively disappeared and were replaced by a low amplitude response in the same location. Our data show that auditory stimuli mimicking ambient sounds efficiently evoke delta-brushes in temporal areas in the premature infant before 35 PMW. Along with findings in other sensory modalities (visual and somatosensory), these findings suggest that sensory driven delta-brushes represent a ubiquitous feature of the human sensory cortex during fetal stages and provide a potential test of functional cortical maturation during fetal development.
    PLoS ONE 11/2013; 8(11):e79028. DOI:10.1371/journal.pone.0079028 · 3.23 Impact Factor
Show more


31 Reads
Available from