About this Research Topic
Although sleep and dreaming are often referred to as the last frontiers, there have been major advances in our understanding of these phenomena during the past twenty years. We now have a clear delineation of the three main behavioural states; wakefulness, non-rapid-eye-movement sleep (NREMS), and rapid-eye-movement sleep (REMS). The neural networks underlying these states have largely been mapped out, and the main criteria used to distinguish between them are: electroencephalogram (EEG), awareness and muscle tone.
• Wakefulness exhibits rapid and low-amplitude EEG, awareness and present muscle tone.
• NREMS exhibits slow and high-amplitude EEG, absent awareness and reduced muscle tone.
• REMS exhibits rapid and low-amplitude EEG, absent awareness and absent muscle tone.
Most dreaming occurs during episodes of phasic REMS, which is when saccadic eye movements are observed. REMS dreaming is generated by a distinct neuronal machinery in the brainstem and hypothalamus, although different cortical regions are also involved. Injuries to this machinery lead to distinct neuropsychiatric syndromes, such as REMS behaviour disorder (RBD), sleep paralysis, hypnagogic/hypnopompic hallucinations, lucid dreaming, and nightmares.
RBD reflects the absence of muscle atonia during REMS dreaming, leading to motor activity and acting out of dream contents that may result in injuries to self and others. Sleep paralysis and hypnagogic/hypnopompic hallucinations are due to the intrusion of REMS into wakefulness at the sleep/wakefulness boundary. Sleep paralysis results from the intrusion of atonia, while hallucinations result from the intrusion of dreaming into wakefulness. Lucid dreaming reflects the intrusion of wakefulness into REMS dreaming. Lastly, nightmares reflect enrichment of REMS dreaming by fear and anxiety that charge up the dreams with fearful/threatening content.
While there is some understanding of the pathology causing some of these syndromes (e.g. RBD as harbinger of Parkinson’s disease), the brain mechanisms underlying them are yet to be fully clarified. Another area that requires further exploration is the pharmacology of REMS dreaming, due to the complexity of the neural network involved.
There is a two-way relationship between dream science and the clinical neuropsychiatry of dream-related disorders: discoveries in the laboratory can help make sense of the most bizarre clinical manifestations (e.g. sleep paralysis), and description of the clinical presentation of a disorder (“nature’s experiment”, e.g. RBD) can give impetus for laboratory exploration. The purpose of this Research Topic is to obtain a cross section of the current field of dream-related disorders, and thus promote the dialogue between dream science and clinical neuropsychiatry. Some of the themes to be explored are:
• relationship between dreams and hallucinations;
• dreams and psychosis;
• mechanism of REMS atonia and its loss in RBD;
• experimental and pathological lesions in the REMS circuitry;
• modification of dreaming by drugs: dream suppressors and inducers;
• relationship between nightmares and fearful sleep paralysis.
Colleagues are encouraged to consider submitting either original or review papers within the scope of this Research Topic.
The authors have read the journal’s policy and have the following potential conflicts: S.R. Pandi-Perumal is a stockholder and the President and Chief Executive Officer of Somnogen Canada Inc., a Canadian Corporation. This affiliation of SRP with Somnogen, does not alter the authors' adherence to Frontiers policies on sharing data and/or materials. He declares that he has no competing interests that might be perceived to influence the content and handling the editorial aspects of this Research Topic.
Other remaining editors declare that they have no proprietary, financial, professional, or any other personal interest of any nature or kind in any product or services and/or company, that could be construed or considered as a potential conflict of interest that might have influenced the views expressed in the proposed Research Topic.
[Image by Henry Fuseli, The Nightmare , 1781, oil on canvas. Detroit Institute of Arts, Founders Society Purchase with funds from Mr. and Mrs. Bert L. Smokler and Mr. and Mrs. Lawrence A. Fleischman, 55.5.A.]
Keywords: Dreaming, REM Sleep, Sleep Paralysis, RBD, Nightmares
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