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This chapter reviews the techniques currently applied to study brain function during sleep deprivation (SD) as opposed to the consequence of SD. It provides a bird's eye view of functional imaging studies performed on healthy young adult volunteers to date and comment on how this research has evolved the conceptualization of how SD modulates behavior. The first functional imaging studies involving SD utilized positron emission tomography (PET). Based on the initial findings, cognitive domain and task difficulty was proposed as determinants of the neural response to SD. It was postulated that changes in dopamine signaling in the SD state contributed to the change in functional connectivity, an idea reprised when discussing risky decision making in SD. The interaction of SD and circadian effects, including the effects of chronotype, could be a further target of functional neuroimaging studies, including the effect of countermeasures such as naps and stimulants.
This chapter shows that the study of dreams provides meaningful and valuable information about cognitive and affective processes occurring during sleep. It demonstrates that typical features in large dream samples can be identified using statistical methods and that these features are in good correspondence with known patterns of brain activity during sleep, in particular rapid eye movement (REM) sleep. These analyses are based on the frequency of occurrence and degree of uniformity of dream contents, irrespective of whether the dreams mimicked real-life experiences or were extremely bizarre. The chapter also shows that bizarre but common aspects in dreams have much in common with known neuropsychological syndromes. Integrated approach to sleep and dreaming undoubtedly contribute to redefining the links between brain processes and the varieties of dream experiences, and lead to a more comprehensive model of human brain function during sleep.
This chapter reviews the techniques currently applied to study brain function during sleep deprivation (SD) as opposed to the consequence of SD. It provides a bird's eye view of functional imaging studies performed on healthy young adult volunteers to date and comment on how this research has evolved the conceptualization of how SD modulates behavior. The first functional imaging studies involving SD utilized positron emission tomography (PET). Based on the initial findings, cognitive domain and task difficulty was proposed as determinants of the neural response to SD. It was postulated that changes in dopamine signaling in the SD state contributed to the change in functional connectivity, an idea reprised when discussing risky decision making in SD. The interaction of SD and circadian effects, including the effects of chronotype, could be a further target of functional neuroimaging studies, including the effect of countermeasures such as naps and stimulants.
Greater insights into the mechanisms and consequences of sleep and sleep disorders have been achieved through advances in brain imaging methods that describe various aspects of neural function. These are collectively referred to as functional neuroimaging. These include techniques such as PET, fMRI, single-photon emission computed tomography (SPECT), transcranial sonography, magnetoencephalography (MEG), low-resolution brain electromagnetic tomography (LORETA), and combined methods such as combined EEG and fMRI. Extensive applications of brain imaging have been made to help clarify the changes in regional brain function that result from perturbations in either homeostatic or circadian processes, and also have clarified the relationship between these brain changes and the behavioral consequences of these disruptions. The earliest applications of neuroimaging to the study of sleep disorders were those of functional neuroimaging methods to study the global brain states of waking, NREM, and REM sleep. Brain imaging studies have been utilized in narcolepsy and the hypersomnias.
This chapter looks at how different memory systems are influenced by sleep. It describes the currently most-widely accepted model of consolidation of hippocampus-dependent memory. The chapter also looks at human functional magnetic resonance imaging (fMRI) studies which provide evidence that, in fact, memories are re-activated, re-organized, and re-processed during sleep. Reactivation occurs during post-learning sleep, and it seems to be an important component of memory consolidation. In general, it has been found that it occurs in those brain regions most strongly related to the specific learning task. Re-activation could therefore support synaptic consolidation of memory traces. However, recent studies also provide more and more evidence for systems memory consolidation. Looking for signs of re-processing during sleep is the most difficult to do, because based on imaging data alone it is hard to distinguish from re-organization, and there are only few behavioral tasks that are designed to examine such changes.
This chapter discusses imaging studies in insomnia and in association with insomnia complaints in people not diagnosed with insomnia. This review includes studies applying structural and functional MRI, magnetic resonance spectroscopy (MRS), high-density electroencephalography, and transcranial magnetic stimulation (TMS). The studies reviewed have reported almost exclusively on regions of the temporal lobe, frontal lobe, and parietal lobe. These cortical regions are of interest because of their key involvement in the cognitive domains that are most affected in insomnia and after sleep deprivation. For each lobe, the chapter systematically addresses differences between insomniacs and controls and correlations of insomnia symptom severity with brain changes in both insomniacs and people not diagnosed with insomnia. Subsequently, the findings are summarized and interpreted with respect to functional relevance, pitfalls, and conclusions on cause, risk factor, or consequence. Neuroimaging has a high promise to reveal insights into the causes and consequences of insomnia.
This chapter reports results on spontaneous brain activity during wakeful rest. It focuses on findings obtained with electroencephalography (EEG) and functional magnetic resonance imaging (fMRI), either acquired separately or simultaneously. The chapter discusses two approaches to analyze resting state activity with fMRI, namely reverse subtraction (activity correlated with task deactivation) and independent component analysis (ICA)-based region analysis. A third way to explore resting state blood oxygen level-dependent (BOLD) activity is to add information obtained with independent recording modalities, in particular EEG. When EEG and fMRI are recorded simultaneously, fMRI activity patterns associated with EEG-defined brain states can be analyzed. Relaxed wakefulness in the EEG is characterized by alpha and beta band oscillations. A thorough analysis of EEG and fMRI patterns during wakeful rest yields a complex relationship where certain EEG patterns can be associated with different BOLD maps and vice versa.
Greater insights into the mechanisms and consequences of sleep and sleep disorders have been achieved through advances in brain imaging methods that describe various aspects of neural function. These are collectively referred to as functional neuroimaging. These include techniques such as PET, fMRI, single-photon emission computed tomography (SPECT), transcranial sonography, magnetoencephalography (MEG), low-resolution brain electromagnetic tomography (LORETA), and combined methods such as combined EEG and fMRI. Extensive applications of brain imaging have been made to help clarify the changes in regional brain function that result from perturbations in either homeostatic or circadian processes, and also have clarified the relationship between these brain changes and the behavioral consequences of these disruptions. The earliest applications of neuroimaging to the study of sleep disorders were those of functional neuroimaging methods to study the global brain states of waking, NREM, and REM sleep. Brain imaging studies have been utilized in narcolepsy and the hypersomnias.
This up-to-date, superbly illustrated book is a practical guide to the effective use of neuroimaging in the patient with sleep disorders. There are detailed reviews of new neuroimaging techniques – including CT, MRI, advanced MR techniques, SPECT and PET – as well as image analysis methods, their roles and pitfalls. Neuroimaging of normal sleep and wake states is covered plus the role of neuroimaging in conjunction with tests of memory and how sleep influences memory consolidation. Each chapter carefully presents and analyzes the key findings in patients with sleep disorders indicating the clinical and imaging features of the various sleep disorders from clinical presentation to neuroimaging, aiding in establishing an accurate diagnosis. Written by neuroimaging experts from around the world, Neuroimaging of Sleep and Sleep Disorders is an invaluable resource for both researchers and clinicians including sleep specialists, neurologists, radiologists, psychiatrists, psychologists.
Functional neuroimaging studies support a role for sleep in restoration/rejuvenation/growth in broad thalamocortical neural networks that play important roles in waking executive function, attention, concentration, working memory, and emotion regulation. This chapter reviews the use of neuroimaging studies that relate to the brain mechanisms of sleepiness. Narcolepsy is a sleep disorder characterized by recurrent daytime sleep attacks and often cataplexy, sleep onset paralysis and hypnagogic hallucinations. The role of functional neuroimaging studies in human narcoleptic patients further clarifies the mechanisms of the extrahypothalamic manifestations of the illness, such as cataplexy, sleep attacks, and hypnogogic hallucinations. Neuroimaging studies related to pharmacotherapy of narcolepsy may reveal insights into the neurobiology of sleepiness. Pharmaceutical agents that produce alertness have been shown to increase activity in arousal networks that maintain generalized thalamocortical activity, reversing sleepiness associated with pathological conditions. Sleepiness therefore appears intimately related to a loss of function in diffuse thalamocortical networks.
This chapter briefly reviews the use of structural and functional neuroimaging in the assessment and management of parasomnias. The majority of the work in the area of neuroimaging and parasomnias and sleep-related movement disorders has been in the area of RLS and PLMD. The scope of the work performed to date has been driven by, and constrained by, clinical manifestations of the disorder and by the measurements currently available by using neuroimaging tools. The most extensive work has been performed in the area of central dopaminergic dysfunction in these disorders. Neuroimaging methods allow determination of brain volumetric changes in patient samples to see if structural cerebral abnormalities may play a role in the disorder. Low-dose opioid treatment has been used in the management of some RLS patients, and nuclear medicine study reveals regional brain function associated with sleepwalking.
Dream recall decreases with the age of the dreamer in both home and laboratory dreams in both men and women. As the dreamer ages, characters in the dream decrease, the dreamer is less likely to be the center of the dream action, and there are more family characters in the dream report. Social interactions in dreams are more commonly aggressive then friendly and least common are sexual interactions. Aggressive social interactions decreases as the dreamer grows older, while other aspects of the aggressive interactions such as witnessing, victim-hood, and the effect of the sex of the dreamer all change with the age of the dreamer. The style of dreaming changes with the age of the dreamer with men getting more passive in their dreams while women appear to get more active. Disorders of dreaming and specific dream contents, like dreams of lost resources, may well have diagnostic significance.