Bistability breaks-off deterministic responses to intracortical stimulation during non-REM sleep

Andrea Pigorini, Simone Sarasso, Paola Proserpio, Caroline Szymanski, Gabriele Arnulfo, Silvia Casarotto, Matteo Fecchio, Mario Rosanova, Maurizio Mariotti, Giorgio Lo Russo, J. Matias Palva, Lino Nobili, Marcello Massimini*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

106 Citations (Scopus)


During non-rapid eye movement (NREM) sleep (stage N3), when consciousness fades, cortico-cortical interactions are impaired while neurons are still active and reactive. Why is this? We compared cortico-cortical evoked-potentials recorded during wakefulness and NREM by means of time-frequency analysis and phase-locking measures in 8 epileptic patients undergoing intra-cerebral stimulations/recordings for clinical evaluation. We observed that, while during wakefulness electrical stimulation triggers a chain of deterministic phase-locked activations in its cortical targets, during NREM the same input induces a slow wave associated with an OFF-period (suppression of power. >. 20. Hz), possibly reflecting a neuronal down-state. Crucially, after the OFF-period, cortical activity resumes to wakefulness-like levels, but the deterministic effects of the initial input are lost, as indicated by a sharp drop of phase-locked activity. These findings suggest that the intrinsic tendency of cortical neurons to fall into a down-state after a transient activation (i.e. bistability) prevents the emergence of stable patterns of causal interactions among cortical areas during NREM. Besides sleep, the same basic neurophysiological dynamics may play a role in pathological conditions in which thalamo-cortical information integration and consciousness are impaired in spite of preserved neuronal activity.

Original languageEnglish
Pages (from-to)105-113
Number of pages9
Publication statusPublished - 5 May 2015
MoE publication typeA1 Journal article-refereed


  • Causality
  • Consciousness
  • Down-state
  • Intracranial
  • Phase-locking


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