About this Research Topic
Today’s knowledge about the key components of the sleep-wake regulatory systems originates from von Economo’s studies on a specific hypersomnia disorder, encephalitis lethargica. Already in the early 20th century von Economy identified the specific areas of the brain where lesions caused abnormal sleep-wake behaviour. Quite recently, these discoveries have been actualized and more details of the brain circuitries and the neurotransmitters involved in sleep-wake regulation have been described. Nevertheless, the neural substrates that regulate our diurnal regulation of sleep and wakefulness are not yet completely understood.
Still today, hypersomnia disorders can provide novel insights into the brain’s sleep-wake regulatory systems. Narcolepsy, which is characterised by sudden sleep attacks that can appear several times a day, is related to loss of orexin producing neurons in the hypothalamus. The hypothalamus is one important node of one of the two major branches of the ascending arousal system. The other branch involves the thalamus. Another hypersomnia disorder, periodic idiopathic hypersomnia or Kleine-Levin Syndrome (KLS), which is characterised by long sleep periods with duration up to two weeks, has recently been coupled to abnormalities in the thalamus. Thus, we believe that studies of hypersomnia disorders can advance the understanding of processes involved in the brain’s sleep-wake regulatory system. Importantly, at the same time knowledge about these fundamental processes will advance the possibilities of diagnosis and treatment of these patients groups.
Neuroimaging has been identified as a key method to discover functional aspects of the human brain. By functional Magnetic Resonance Imaging (fMRI) regions in the brain that are active during a certain task and regions that are functionally connected to each other can be identified. A complimentary method is Positron Emission Tomography that provides visualisation of neurotransmitter distribution in the brain. These neuroimaging methods have contributed to a renewed view on human brain function. Despite this, the knowledge about the mechanistic relationships behind certain brain activation patterns remains elusive. Here we believe that theoretical neuroscience and mechanistic modelling of brain signals obtained from e.g., fMRI or electroencephalogram (EEG) can provide means to further the knowledge in this field.
This topic aims to gather the most recent neuroimaging research within the field of hypersomnia disorders and to make an inventory of theoretical and applied neuroimaging methods that are available for investigation of brain circuits involved sleep-wake regulation. Researchers with interest in neuroimaging of hypersomnia disorders, such as narcolepsy and KLS, we ask to contribute to this topic. In addition, we welcome researchers with new ideas on how to approach the issue of mechanistic modelling of the sleep-wake regulatory system. Research involving pre-clinical studies of neural circuits with relation to this research topic is also of interest.
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