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

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.

SUBMITTER: Nieminen JO

PROVIDER: S-EPMC4974655 | biostudies-literature | 2016 Aug

REPOSITORIES: biostudies-literature

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

Nieminen Jaakko O JO Gosseries Olivia O Massimini Marcello M Saad Elyana E Sheldon Andrew D AD Boly Melanie M Siclari Francesca F Postle Bradley R BR Tononi Giulio G

Scientific reports 20160805

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 ...[more]

PMID: 27491799

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Project description:BackgroundThe administration of dexmedetomidine is limited to highly monitored care settings because it is only available for use in humans as intravenous medication. An oral formulation of dexmedetomidine may broaden its use to all care settings. The authors investigated the effect of a capsule-based solid oral dosage formulation of dexmedetomidine on sleep polysomnography.MethodsThe authors performed a single-site, placebo-controlled, randomized, crossover, double-blind phase II study of a solid oral dosage formulation of dexmedetomidine (700 mcg; n = 15). The primary outcome was polysomnography sleep quality. Secondary outcomes included performance on the motor sequence task and psychomotor vigilance task administered to each subject at night and in the morning to assess motor memory consolidation and psychomotor function, respectively. Sleep questionnaires were also administered.ResultsOral dexmedetomidine increased the duration of non-rapid eye movement (non-REM) stage 2 sleep by 63 (95% CI, 19 to 107) min (P = 0.010) and decreased the duration of rapid eye movement (REM) sleep by 42 (5 to 78) min (P = 0.031). Overnight motor sequence task performance improved after placebo sleep (7.9%; P = 0.003) but not after oral dexmedetomidine-induced sleep (-0.8%; P = 0.900). In exploratory analyses, we found a positive correlation between spindle density during non-REM stage 2 sleep and improvement in the overnight test performance (Spearman rho = 0.57; P = 0.028; n = 15) for placebo but not oral dexmedetomidine (Spearman rho = 0.04; P = 0.899; n = 15). Group differences in overnight motor sequence task performance, psychomotor vigilance task metrics, and sleep questionnaires did not meet the threshold for statistical significance.ConclusionsThese results demonstrate that the nighttime administration of a solid oral dosage formulation of dexmedetomidine is associated with increased non-REM 2 sleep and decreased REM sleep. Spindle density during dexmedetomidine sleep was not associated with overnight improvement in the motor sequence task.Editor’s perspective

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

Publications

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

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