Cortical gamma oscillations: the functional key is activation, not cognition

Merker, Bjørn

doi:10.1016/j.neubiorev.2013.01.013

Cited by 116 publications

(109 citation statements)

References 278 publications

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“…Thus, the strong decrease in lower-frequency oscillations seen in this study may be indicative of a psilocybin-induced shift of the resting excitation/inhibition balance (E/I balance) toward excitation. This interpretation is also supported by the slight psilocybininduced increase in high-gamma oscillations because gamma oscillations have been strongly associated with neuronal excitation (Merker 2013). Given the crucial role of lowerfrequency oscillations in structuring processes at the cellular level (Haegens et al 2011), the systemic level (Hanslmayr et al 2013), and in consciousness (VanRullen and Koch 2003;Schroeder and Lakatos 2009), any profound decrease in lower-frequency oscillations is likely to disrupt the ordinary temporal structure of neuronal processes.…”

Section: Discussionmentioning

confidence: 91%

Psilocybin-induced spiritual experiences and insightfulness are associated with synchronization of neuronal oscillations

et al. 2015

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Section: Discussionmentioning

confidence: 91%

Psilocybin-induced spiritual experiences and insightfulness are associated with synchronization of neuronal oscillations

et al. 2015

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“…While many of the low-frequency oscillations have been associated with functional inhibition, faster gamma-band oscillations are believed to reflect cortical activation (Merker, 2013). Depending on the exact cortical region, gamma oscillations are closely related to attentive processing of information (Fries et al, 2001;Womelsdorf and Fries, 2006), active maintenance of memory contents (Herrmann et al, 2004), conscious perception (Singer, 2001).…”

Section: Gamma Oscillationsmentioning

confidence: 99%

EEG oscillations: From correlation to causality

Herrmann¹,

Strüber

Helfrich

et al. 2016

International Journal of Psychophysiology

399

306

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“…22,23 More recent work, however, has shown that gamma synchrony can persist, or even increase, under general anesthesia, 106 and the significance of gamma coherence for consciousness has been questioned in general. 107 According to a recent framework from cognitive psychology, binding would depend on top-down signals that selectively reinforce and sustain those representations in the early sensory cortices that encode aspects of sensory information that belong together. 108 In keeping with this development, and with the evidence implicating disrupted top-down connectivity in anesthesia-induced loss of consciousness, Mashour has reformulated his "unbinding paradigm" to move the focus away from gamma coherence toward top-down integration.…”

Section: Integrating the Present Hypothesis With Existing Framework mentioning

confidence: 99%

The Role of Dendritic Signaling in the Anesthetic Suppression of Consciousness

Meyer

2015

Anesthesiology

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Despite considerable progress in the identification of the molecular targets of general anesthetics, it remains unclear how these drugs affect the brain at the systems level to suppress consciousness. According to recent proposals, anesthetics may achieve this feat by interfering with corticocortical topdown processes, that is, by interrupting information flow from association to early sensory cortices. Such a view entails two immediate questions. First, at which anatomical site, and by virtue of which physiological mechanism, do anesthetics interfere with top-down signals? Second, why does a breakdown of top-down signaling cause unconsciousness? While an answer to the first question can be gleaned from emerging neurophysiological evidence on dendritic signaling in cortical pyramidal neurons, a response to the second is offered by increasingly popular theoretical frameworks that place the element of prediction at the heart of conscious perception. Science magazine posed this question in a special section titled "What don't we know?," dedicated to the greatest challenges of contemporary science. 1 "Scientists are chipping away at the drugs' effects on individual neurons," the article reads, "but understanding how they render us unconscious will be a tougher nut to crack." This prediction proved correct: a decade later, we have expanded considerably our knowledge of the molecular targets of general anesthetics, but it remains enigmatic how these drugs affect the brain at the systems level. Why does the potentiation of γ-aminobutyric acid (GABA) receptors caused by propofol or desflurane cause unconsciousness? How are the brain's computational processes affected by this and other molecular mechanisms of anesthetics, so that patients undergoing surgery cease to experience their surrounds in terms of sight, sound, and touch? Anesthesiologists and cognitive neuroscientists alike have been captivated by these questions and have proposed a number of models in an attempt to answer them, such as Flohr's "information processing theory of anesthesia," 2 Alkire's "thalamic consciousness switch hypothesis," 3-6 Mashour's "cognitive unbinding paradigm," 7,8 John and Prichep's "anesthetic cascade," 9 or Hudetz's "forgotten present." 10,11 We shall return to some of these frameworks in a later section of the article.One recent development is particularly intriguing. Given that the most striking feature of general anesthesia is an interruption of the patient's ability to perceive the environment, it would appear intuitive for anesthetics to interfere primarily with bottom-up information flow along the sensory pathways, that is, with the signals that carry perceptual information from the thalamus to the primary sensory cortices and on to unimodal and multimodal association cortices. However, the very opposite appears to be the case. Several recent studies-carried out in both humans and animals, and using a variety of different anesthetic agents-have investigated differences in directional corticocortical connectivity bet...

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Cortical gamma oscillations: the functional key is activation, not cognition

Cited by 116 publications

References 278 publications

Psilocybin-induced spiritual experiences and insightfulness are associated with synchronization of neuronal oscillations

Psilocybin-induced spiritual experiences and insightfulness are associated with synchronization of neuronal oscillations

EEG oscillations: From correlation to causality

The Role of Dendritic Signaling in the Anesthetic Suppression of Consciousness

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