Consciousness and cortical responsiveness: A within-state study during non-rapid eye movement sleep

Research output: Contribution to journalArticleScientificpeer-review

Researchers

  • Jaakko Nieminen

  • Olivia Gosseries
  • Marcello Massimini
  • Elyana Saad
  • Andrew D. Sheldon
  • Melanie Boly
  • Francesca Siclari
  • Bradley R. Postle
  • Giulio Tononi

Research units

  • University of Wisconsin-Madison
  • University of Liege
  • IRCCS Fondazione Don Carlo Gnocchi - Milano
  • University of Lausanne

Abstract

When subjects become unconscious, there is a characteristic change in the way the cerebral cortex responds to perturbations, as can be assessed using transcranial magnetic stimulation and electroencephalography (TMS-EEG). For instance, compared to wakefulness, during non-rapid eye movement (NREM) sleep TMS elicits a larger positive-negative wave, fewer phase-locked oscillations, and an overall simpler response. However, many physiological variables also change when subjects go from wake to sleep, anesthesia, or coma. To avoid these confounding factors, we focused on NREM sleep only and measured TMS-evoked EEG responses before awakening the subjects and asking them if they had been conscious (dreaming) or not. As shown here, when subjects reported no conscious experience upon awakening, TMS evoked a larger negative deflection and a shorter phase-locked response compared to when they reported a dream. Moreover, the amplitude of the negative deflection-a hallmark of neuronal bistability according to intracranial studies-was inversely correlated with the length of the dream report (i.e., total word count). These findings suggest that variations in the level of consciousness within the same physiological state are associated with changes in the underlying bistability in cortical circuits.

Details

Original languageEnglish
Article number30932
Pages (from-to)1-10
JournalScientific Reports
Volume6
Publication statusPublished - 5 Aug 2016
MoE publication typeA1 Journal article-refereed

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