Zusammenfassung
Bewusstsein (lat. conscientia = Mitwissen oder Gewissen) ist nach aktueller Definition die Erkenntnis des Selbst und seiner Umgebung; es beschreibt den Grad in dem ein Organismus Reize empfindet und wach ist. Dieser biologische Begriff für die komplexen neuronalen Prozesse, die in einem Individuum die äußere und innere Umwelt zu erkennen und danach zu handeln gestatten, war und ist eines der größten Probleme von Philosophie und Naturwissenschaft.
Neuronale Substrate umfassen mehrere Funktionskreise, die hierarchisch organisiert sind und dynamisch zusammenarbeiten. Unterste Ebene ist das aufsteigende retikuläre Aktivierungssystem in der mesenzephalen Formatio reticularis, das über den Thalamus diffus zur Großhirnrinde, über den Hypothalamus zum basalen Vorderhirn und zum limbischen System projiziert. Es fungiert als Kontrollsystem der kortikalen Aktivität; seine Reizung produziert die Arousalreaktion als elektrisches Korrelat des Bewusstseins; seine Zerstörung erzeugt Koma. Oberste Ebene sind kortikale (präfrontale und Assoziations-) Netzwerke für Erkennung, Motorik, Langzeitgedächtnis und Aufmerksamkeit. Die Grade des Bewusstseins reichen von Hypervigilität über Somnolenz, Delirium bis zum Koma mit seinen Unterstufen. Elektrophysiologische und moderne bildgebende Befunde weisen auf relevante morphologische Funktionen hin. Grundlagen und Pathophysiologie des Bewusstseins liegen im Fokus moderner neurowissenschaftlicher Forschung.
Summary
Consciousness (Latin conscietia = moral conscience) is currently defined as a continuous state of full awareness of the Self and one’s relationship to the external and internal environment. This widely discussed biological term for complex neuronal processes, that allow an individual to recognize itself and its environment and to act accordingly, has been, and still is, the subject of much research in philosophy and natural sciences as well as neuroscience.
Neuronal substrates include several functional networks that are hierarchically organized and cooperate functionally. The lowest level is the mesencephalic ascending reticular system in the reticular formation and its projection via the reticular thalamus to the cerebral cortex. It further projects via the hypothalamus to the basal forebrain and limbic system and to the medial raphe of the brainstem. Its principal function is to focus our alertness on specific stimuli or internal processes as a control system of the neuronal activity of the cortex. Stimulation of the ARAS produces arousal reactions as the electric correlate of consciousness; its destruction causes coma and related states. The highest level is a cortical (prefrontal and association) network for recognition, motor activity, long-term memory, and attention. The different levels of consciousness range from hyperactivation via alertness, somnolence, delirium to coma and its subtypes. The relevant morphologic lesions can be detected by electrophysiological and modern neuroimaging studies. The bases and pathophysiology of consciousness, its cognitive aspects and major disorders are the focus of current scientific research.
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Jellinger, K.A. Der Geist im Gehirn – Teil 2. Psychopraxis 13, 30–35 (2010). https://doi.org/10.1007/s00739-010-0193-9
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DOI: https://doi.org/10.1007/s00739-010-0193-9