Physiological Determinants of Consciousness

Abstract

It is taken for granted that everyone has a rough idea of what is meant by consciousness, but we know as long as no one asks us to define it (1). This is why some consider that “it is better to avoid a precise definition of consciousness because of the dangers of a premature definition” (2). Still, many theoretical writers and even some basic neuroscientists play with the global notion of consciousness in very different ways. For most authors, the notion covers sensations, mental images, thoughts, and volition. Special emphasis was also placed on emotions and feelings as important components of consciousness toward the emergence of self (3,4). In dictionaries, consciousness is simply defined as the state of being awake or, sometimes more subtly, as an organism’s awareness of its own self and surroundings. Awareness exists in animals, whereas self-awareness and evolved forms of consciousness that implicate complex plans in anticipated future probably restrict this notion to humans. The view that consciousness depends on awareness and arises from a background of brain arousal led most commentators to conclude that consciousness is what abandons us every evening and reappears the next morning when we wake up. However, peculiar types of consciousness, such as mentation with illogical thought and bizarre feelings, occur during dreaming in rapid-eye-movement (REM) sleep, whereas during deep stages of slow-wave sleep (SWS) dream mentation is much closer to real life (5–7).