The question of how “consciousness” can be scientifically investigated is extraordinarily complex. It cannot be answered from a neuroscientific, psychological or philosophical point of view alone. Even the object of such an investigation becomes blurred in the arbitrariness of the understanding of what consciousness is. As early as 1913, the psychologist Watson came to the conclusion that concepts such as consciousness were unscientific ballast that had no place in science. “For the representatives of such psychologies “…do not tell us what consciousness is, but simply begin to put something into it” (Watson 1968). This criticism has not become obsolete even today.
A serious scientific examination of the question of what consciousness, subjective sensations and the like are, and what their neurobiological correlates are, must try to adequately specify these concepts and indicate the criteria by which it can be determined whether a human or animal performance is conscious or accompanied by a subjective experience, or whether it is a performance that takes place without consciousness or subjective sensation. Only this specification is a prerequisite for the fact that the neurobiological processes that characterize consciousness can be scientifically investigated and that the neurobiological processes that characterize consciousness become recognizable at all.
The concept of consciousness was clarified within the framework of methodological and neuropsychological investigations. In brain-damaged patients it was shown how the development of a conscious visual impression can be quantitatively measured in contrast to an unconscious processing of visual stimuli in the brain and which are the underlying neuronal processes. The results were described in :
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Die Natur des Bewusstseins
Verlag C.H. Beck
Wie Wahrnehmung und freier Wille im Gehirn entstehen
One of the most difficult to comprehend changes in consciousness that can be triggered by brain damage is the lack of awareness of the existence of one half of the room and/or body, a disorder known as “neglect”. The patients no longer direct their head and eyes into one half of the room, objects in this half of the room are ignored as if they did not exist. Thus, for example, only food is eaten on the right half of a plate, while drawing an object, its left side is not displayed. Patients do not wash or dress one half of their body and shave only one half of their face. They are not able to find the arm of one half of the body or an object e.g. to the left of it. They do not express themselves about one half of a room and/or body and do not seem to understand other people’s expressions about one half of a room or about one of their body halves. Despite normal intelligence, the patients behave as if one half of the room and/or body had ceased to exist. Within the framework of a research project, the diagnostic criteria for this disorder were specified, the numerous different phenomena in which the disorder is expressed and the neuronal basis of the disorder were investigated. The results have been described in :
Neglect nach Hirnschädigung
Unilaterale Verminderung der Aufmerksamkeit und Raumrepräsentation
Verlag C. H. Beck
A literary description of the most essential phenomena can also be found in:
Berichte vom Rande des Bewusstseins
Verlag C. H. Beck