Axel Steiger

Consciousness is a multifaceted concept; its different aspects vary across species, vigilance states or health conditions. While basal aspects of consciousness like perceptions and emotions are present in many states and species, higher-order aspects like reflective or volitional capabilities seem to be most pronounced in awake humans. Here we assess the experience of volition across different states of consciousness: 10 frequent lucid dreamers rated different aspects of volition according to the Volitional Components Questionnaire for phases of normal dreaming, lucid dreaming and wakefulness. Overall, experienced volition was comparable for lucid dreaming and wakefulness, and rated significantly higher for both states compared to non-lucid dreaming. However, three subscales showed specific differences across states of consciousness: planning ability was most pronounced during wakefulness, intention enactment most pronounced during lucid dreaming, and self-determination most pronounced during both wakefulness and lucid dreaming. Our data confirm the multifaceted nature of consciousness: different higher-order aspects of consciousness are differentially expressed across different conscious states.

In patients with depression, characteristic changes of sleep electroencephalogram and nocturnal hormone secretion occur including rapid eye movement (REM) sleep disinhibition, reduced non-REM sleep and impaired sleep continuity. Neuropeptides are common regulators of the sleep electroencephalogram (EEG) and nocturnal hormone secretion and changes in their activity appear to contribute to the aberrances of sleep in affective disorders. A reciprocal interaction of the sleep-promoting growth hormone-releasing hormone (GHRH) and corticotrophin-releasing hormone (CRH), which promotes wakefulness and REM sleep, plays a key role in sleep regulation, at least in male subjects. Also galanin and ghrelin promote sleep in men. Neuropeptide Y is involved in the timing of sleep onset. The effects of peptides of sleep are influenced by the time of administration, age, gender and depression. In healthy subjects and in remitted depressed patients motoric memory learning is consolidated during sleep. This effect is absent in depressed patients who are at least 30 years old, and is probably related to elevated glucocorticoid levels.

Schlaf ist eine Zeit hoher Aktivität in endokrinen Systemen. Entsprechend besteht eine bidirektionale Interaktion zwischen der elektrophysiologischen und der endokrinen Komponente des Schlafs, die sich simultan mit Polysomnographie und nächtlichen Blutabnahmen zur späteren Hormonbestimmung erfassen lassen. Klinische Studien, Humanexperimente und Tiermodelle zeigen, dass Neuropeptide und Steroide eine wichtige Rolle in der normalen Schlafregulation spielen. Bei endokrinologischen Erkrankungen und der Depression trägt die gestörte Hormonsekretion zu Veränderungen der Schlafstruktur bei. Eine reziproke Interaktion zwischen den Neuropeptiden Wachstumshormon-freisetzendes Hormon (GHRH) und Corticotropin-freisetzendes Hormon (CRH) spielt eine Schlüsselrolle in der Schlafregulation.

The neuropeptide ghrelin is a major signal for food intake in various species including humans. After exogenous ghrelin administration, food intake and body weight increase in rodents. In normal human subjects, ghrelin administration increases self‐rated appetite and calorie intake and prompts the imagination of favorite meals. It is unclear so far whether ghrelin levels are affected by external cues such as sight of food. We investigated the influence of pictures showing food compared to neutral pictures on ghrelin levels in young normal male subjects (n = 8). The study consisted of two consecutive sessions with a one‐week interval. During each session, blood for later analysis of plasma concentrations of ghrelin was collected between 08:15 and 13:00 every 15 min (between 10:30 and 11:30 every 10 min). Breakfast and lunch was provided at 08:30 and 12:00, respectively. Fifty pictures were presented from 10:30 to 10:45 showing neutral images during the first session and food contents during the second session. As expected, ghrelin levels increased before each meal independent of the picture contents. In addition, ghrelin levels during the 30‐min interval following the presentation of pictures with food increased significantly compared to the 30‐min interval before this presentation (area under the curve (AUC): 188 % vs. 158 %, P < 0.05). The difference in the increases between the two picture conditions was also significant (P < 0.05). Our findings suggest that sight of food elevates ghrelin levels in healthy volunteers.

Neuroendocrine changes in depression have long been recognized, with a focus mainly on hypercortisolism. The other hormone of the hypothalamus-pituitary adrenocortical system, aldosterone, has been widely neglected. Here we summarize the involvement of the renin-angiotensin-aldosterone system (RAAS) and the regulation of aldosterone in health with a particular focus on sleep-related changes and its role in stress-related conditions, like major depression. We highlight its role in functional systems which could be relevant in the therapy for refractory depression, like inflammatory mechanisms, the monoaminergic and the glutamatergic systems. Furthermore, anatomic areas which specifically mediate the action of aldosterone have been identified. In particular the nucleus of the solitary tract (NTS) seems to have an important role and appears to be a target for antidepressive manipulations, like vagus nerve stimulation. Clinical data demonstrating the efficacy of aldosterone-reducing strategies for specific depressive syndromes are reviewed. In particular aspects of differentiation between melancholic vs. atypical depression spectrum disorders are discussed.

The diagnosis of mental illness is frequently accompanied by sleep problems; conversely, people experiencing sleep problems may subsequently develop mental illness. Sleep and Mental Illness looks at this close correlation and considers the implications of research findings that have emerged in the last few years. Additionally, it surveys the essential concepts and practical tools required to deal with sleep and co-morbid psychiatric problems. The volume is divided into three main sections: basic science, neuroendocrinology, and clinical science. Included are over 30 chapters on topics such as neuropharmacology, insomnia, depression, dementia, autism, and schizophrenia. Relevant questionnaires for the assessment of sleep disorders, including quality-of-life measurement tools, are provided. There is also a summary table of drugs for treating sleep disorders. This interdisciplinary text will be of interest to clinicians working in psychiatry, behavioral sleep medicine, neurology, pulmonary and critical care medicine.