The dataset contains EEG recordings pre- (with the presleep tag), during (with the sleep tag) and post- (with the postsleep tag) sleep during a evening to morning experimental session. During the EEG recordings, participants were exposed to sounds with various emotional intensity. Half of the stimuli were pseudo-words uttered with an angry or neutral voice. Details about these stimuli can be found here: https://doi.org/10.1093/texcom/tgac003. The other half of the stimuli were vocalizations shouted loudly or screamed. For more information by https://doi.org/10.1016/j.cub.2015.06.043
Abstract Motor imagery (MI) is known to engage motor networks and is increasingly used as a relevant strategy in functional rehabilitation following immobilization, whereas its effects when applied during immobilization remain underexplored. Here, we hypothesized that MI practice during 11 h of arm-immobilization prevents immobilization-related changes at the sensorimotor and cortical representations of hand, as well as on sleep features. Fourteen participants were tested after a normal day (without immobilization), followed by two 11-h periods of immobilization, either with concomitant MI treatment or control tasks, one week apart. At the end of each condition, participants were tested on a hand laterality judgment task, then underwent transcranial magnetic stimulation to measure cortical excitability of the primary motor cortices (M1), followed by a night of sleep during which polysomnography data was recorded. We show that MI treatment applied during arm immobilization had beneficial effects on (1) the sensorimotor representation of hands, (2) the cortical excitability over M1 contralateral to arm-immobilization, and (3) sleep spindles over both M1s during the post-immobilization night. Furthermore, (4) the time spent in REM sleep was significantly longer, following the MI treatment. Altogether, these results support that implementing MI during immobilization may limit deleterious effects of limb disuse, at several levels of sensorimotor functioning.
The waking brain efficiently detects emotional signals to promote survival. However, emotion detection during sleep is poorly understood and may be influenced by individual sleep characteristics or neural reactivity. Notably, dream recall frequency has been associated with stimulus reactivity during sleep, with enhanced stimulus-driven responses in high vs. low recallers. Using electroencephalography (EEG), we characterized the neural responses of healthy individuals to emotional, neutral voices, and control stimuli, both during wakefulness and NREM sleep. Then, we tested how these responses varied with individual dream recall frequency. Event-related potentials (ERPs) differed for emotional vs. neutral voices, both in wakefulness and NREM. Likewise, EEG arousals (sleep perturbations) increased selectively after the emotional voices, indicating emotion reactivity. Interestingly, sleep ERP amplitude and arousals after emotional voices increased linearly with participants' dream recall frequency. Similar correlations with dream recall were observed for beta and sigma responses, but not for theta. In contrast, dream recall correlations were absent for neutral or control stimuli. Our results reveal that brain reactivity to affective salience is preserved during NREM and is selectively associated to individual memory for dreams. Our findings also suggest that emotion-specific reactivity during sleep, and not generalized alertness, may contribute to the encoding/retrieval of dreams.
Sleep leads to a disconnection from the external world. Even when sleepers regain consciousness during rapid eye movement (REM) sleep, little, if any, external information is incorporated into dream content [1Dement W. Wolpert E.A. The relation of eye movements, body motility, and external stimuli to dream content.J. Exp. Psychol. 1958; 55: 543-553Crossref PubMed Scopus (207) Google Scholar, 2Rechtschaffen A. Foulkes D. Effect of visual stimuli on dream content.Percept. Mot. Skills. 1965; 20: 1149-1160Crossref PubMed Scopus (32) Google Scholar, 3Berger R.J. Experimental modification of dream content by meaningful verbal stimuli.Br. J. Psychiatry. 1963; 109: 722-740Crossref PubMed Scopus (64) Google Scholar]. While gating mechanisms might be at play to avoid interference on dreaming activity [4Nir Y. Tononi G. Dreaming and the brain: from phenomenology to neurophysiology.Trends Cogn. Sci. 2010; 14: 88-100Abstract Full Text Full Text PDF PubMed Scopus (311) Google Scholar], a total disconnection from an ever-changing environment may prevent the sleeper from promptly responding to informative events (e.g., threat signals). In fact, a whole range of neural responses to external events turns out to be preserved during REM sleep [5Issa E.B. Wang X. Sensory responses during sleep in primate primary and secondary auditory cortex.J. Neurosci. 2008; 28: 14467-14480Crossref PubMed Scopus (81) Google Scholar, 6Nir Y. Vyazovskiy V.V. Cirelli C. Banks M.I. Tononi G. Auditory responses and stimulus-specific adaptation in rat auditory cortex are preserved across NREM and REM sleep.Cereb. Cortex. 2015; 25: 1362-1378Crossref PubMed Scopus (62) Google Scholar, 7Perrin F. García-Larrea L. Mauguière F. Bastuji H. A differential brain response to the subject's own name persists during sleep.Clin. Neurophysiol. 1999; 110: 2153-2164Crossref PubMed Scopus (219) Google Scholar, 8Blume C. Del Giudice R. Wislowska M. Heib D.P.J. Schabus M. Standing sentinel during human sleep: continued evaluation of environmental stimuli in the absence of consciousness.Neuroimage. 2018; 178: 638-648Crossref PubMed Scopus (18) Google Scholar, 9Strauss M. Sitt J.D. King J.R. Elbaz M. Azizi L. Buiatti M. Naccache L. van Wassenhove V. Dehaene S. Disruption of hierarchical predictive coding during sleep.Proc. Natl. Acad. Sci. USA. 2015; 112: E1353-E1362Crossref PubMed Scopus (106) Google Scholar]. Thus, it remains unclear whether external inputs are either processed or, conversely, gated during REM sleep. One way to resolve this issue is to consider the specific impact of eye movements (EMs) characterizing REM sleep. EMs are a reliable predictor of reporting a dream upon awakening [10Dement W. Kleitman N. The relation of eye movements during sleep to dream activity: an objective method for the study of dreaming.J. Exp. Psychol. 1957; 53: 339-346Crossref PubMed Scopus (509) Google Scholar, 11Goodenough D.R. Shapiro A. Holden M. Steinschriber L. A comparison of" dreamers" and" nondreamers": Eye movements, electroencephalograms, and the recall of dreams.J. Abnorm. Soc. Psychol. 1959; 59: 295Crossref Scopus (58) Google Scholar], and their absence is associated with a lower arousal threshold to external stimuli [12Ermis U. Krakow K. Voss U. Arousal thresholds during human tonic and phasic REM sleep.J. Sleep Res. 2010; 19: 400-406Crossref PubMed Scopus (77) Google Scholar]. We thus hypothesized that the presence of EMs would selectively prevent the processing of informative stimuli, whereas periods of REM sleep devoid of EMs would be associated with the monitoring of external signals. By reconstructing speech in a multi-talker environment from electrophysiological responses, we show that informative speech is amplified over meaningless speech during REM sleep. Yet, at the precise timing of EMs, informative speech is, on the contrary, selectively suppressed. These results demonstrate the flexible amplification and suppression of sensory information during REM sleep and reveal the impact of EMs on the selective gating of informative stimuli during sleep.
Abstract The scientific literature suggests that emotional memories benefit from a privileged consolidation over neutral memories. This effect extends to consolidation processes that occur during sleep. Indeed, during sleep, a complex set of oscillations (namely slow-oscillations, theta rhythm and spindles) mediates the communication between brain regions involved in the long-term integration of memories. However, whether sleep oscillations may contribute to the reactivation and consolidation of emotional memories in humans is still unclear. Because non-invasive electroencephalography (EEG) has limited access to deep brain regions implicated in memory and emotion (e.g., hippocampus, amygdala, orbitofrontal cortex), here we recorded EEG signal from these brain regions using intracranial electrodes placed in medically-resistant epileptic patients in the context of presurgical investigation. During wakefulness, we presented the patients with emotional (i.e., humorous) vs emotionally neutral pictures paired with a sound. Then, we tested for the reinstatement of emotional-associations by delivering the sound during a subsequent period of sleep. We found that the reactivation of emotional (compared to neutral) memories during sleep enhanced slow-oscillation and spindle activity in the orbitofrontal cortex, paralleled with an increase in theta connectivity between the hippocampus and the orbitofrontal cortex. In addition, we observed that the theta response to emotional memories reactivated at subsequent wake was different than for neutral memories, suggesting a change in memory traces with targeted memory reactivation. These data suggest that consolidation of emotional events during sleep is due to a larger expression of sleep features (in the slow-oscillation, theta and sigma frequency bands) and that the mechanisms of brain plasticity also take place in emotional brain regions during NREM sleep.
The dataset contains EEG recordings pre- (with the presleep tag), during (with the sleep tag) and post- (with the postsleep tag) sleep during a evening to morning experimental session. During the EEG recordings, participants were exposed to sounds with various emotional intensity. Half of the stimuli were pseudo-words uttered with an angry or neutral voice. Details about these stimuli can be found here: https://doi.org/10.1093/texcom/tgac003. The other half of the stimuli were vocalizations shouted loudly or screamed. For more information by https://doi.org/10.1016/j.cub.2015.06.043
Sleep leads to a disconnection from the external world. Even when sleepers regain consciousness during Rapid Eye Movement (REM) sleep, little, if any, external information is incorporated into dream content. While gating mechanisms might be at play to avoid interference on dreaming activity, a total disconnection would prevent the sleeper from promptly responding to informative events (e.g., threat signals). In fact, a whole range of neural responses to external events are preserved, at least partially, during REM sleep. Thus, it remains unsettled whether external inputs are either integrated or conversely gated during REM sleep. Here, we sought to disentangle this issue by studying the impact of eye movements (EMs) on the processing of informative signals. EMs constitute a reliable predictor of reporting a dream upon awakening and induce a higher arousal threshold to external stimuli. We hypothesized that although sleepers might continue responding to external events, periods of EMs would be associated with the gating of informative signals in order to reduce interference with dreaming activity. By reconstructing perceived speech in a multi-talker, cocktail-party environment from electrophysiological responses, we show that informative speech is selectively amplified over meaningless speech during REM sleep. However, we show that at the precise timing of EMs, informative speech is, on the contrary, selectively suppressed. Importantly, this suppression did not affect the processing of non-informative signals, revealing a selective mechanism of gating for informative contents rather than a general decline in sensory encoding. These results reveal flexible mechanisms of amplification/suppression of external inputs during REM sleep, and demonstrate the impact of EMs on the selective gating of informative stimuli.
ABSTRACT During sleep, recognizing threatening signals is crucial to know when to wake up and when to continue vital sleep functions. Screaming is perhaps the most salient and efficient signal for communicating danger at a distance or in conditions of limited visibility. Beyond the intensity or the pitch of the sound, rapid modulations of sound pressure in the so-called roughness range ( i.e. 30-150 Hz ) are particularly powerful in capturing attention and accelerating reactions. Roughness is an acoustic feature that characterizes alarm signals such as screams. However, whether rough sounds are also processed in a privileged manner during sleep is unknown. We tested this hypothesis by stimulating sleeping human participants with low-intensity screams and neutral calls. We found that screams trigger more reliable and better time-locked responses in wakefulness and NREM sleep. In addition, screams boosted sleep spindles, suggesting elevated stimulus salience. The increase in sleep spindle power was linearly proportional to the roughness of vocalizations, but not to their pitch. These findings demonstrate that, even at low sound intensity, scream’s roughness conveys stimulus relevance and enhances processing in both the waking and sleeping states. Preserved differential neural responses based on stimulus salience may ensure adaptive reactions –and ultimately survival– in a state where the brain is mostly disconnected from external inputs.
