How exactly the different centres of the human brain work together will remain a mystery for a long time to come because of their unimaginable complexity. Nevertheless, there are partial advances in neurological research that bring us a big step closer to understanding certain brain functions. An article by the two brain researchers Joshua Brown and Todd Braver from Washington University in St. Louis, published in 2005 in the leading American science magazine “Science”, shed new light on the relationship between unconscious and conscious processes in our central nervous system. What they found out with the help of functional magnetic resonance imaging (fMRI) in the brains of experimental subjects has now sparked new discussions at a scientific congress in Washington.
Ever since Siegmund Freud and Carl Gustav Jung “discovered” the unconscious, but at the latest since the long misinterpreted neurophysiological experiments of Benjamin Libet (1916-2007), man is no longer regarded as the master of his own ego. Libet’s subjects were asked to move a wrist at a freely selectable time. They were to remember the time of their decision by means of a moving point on the screen of an oscillograph. According to the test participants, the decision to live the wrist was made about 200 milliseconds before the beginning of the action. Using electrodes on the skull, however, Libet found that 350 milliseconds earlier, i.e. a total of 550 milliseconds before the beginning of the action, a so-called “readiness potential” had built up in the neural circuits responsible for the hand movement. In reality, the decision to move a wrist was therefore made unconsciously, even though the subjects had perceived the decision as completely free and conscious.
Libet was able to show that this incorrect perception is created by an automatic backdating of the decision. He was also able to demonstrate that the test persons were able to stop unconsciously initiated actions by means of a deliberate veto until a certain point in time. In his opinion, this veto option is an important aspect of free will. He therefore emphatically rejected materialistic or Marxist colleagues who had tried to derive from his famous experiment a refutation of the Christian-Western doctrine of free will.
In his book “Mind Time”, published in English in 2004 and in German in 2005, Libet presented his Time-on-Theory, according to which all conscious thoughts, plans and feelings begin unconsciously. Fast reactions in sports (e. g. when hitting back a 160km/h tennis ball) can only occur unconsciously. These actions only become conscious when the action has already been completed. He assumed that the subjective consciousness is essentially non-physical in nature and therefore cannot be reduced to neuronal functions. Libet stressed that the materialistic determinism is based just as much on non-falsifiable assumptions as its counterpart, the idealistic dualism of body and soul.
Libet was convinced that the contents of consciousness are independent of neuronal functions, for he didn’t know of any experiment that provided clues to the contrary. Indeed, epileptic patients who have had the connection between the two hemispheres of the cerebrum (corpus callosum) cut for therapeutic reasons (“split brain”) still feel that they have a unified self. Neither do they see double, nor do they feel antagonistic drives of action. As Libet himself was able to show, conscious experience is also independent of the process of memory formation. In this respect, the German subtitle of Libet’s book (“How the brain produces consciousness”) is misleading. Libet himself put “produces”, cautious as he was, in quotation marks. He merely assumed that consciousness, in accordance with his experiments, “is the emergent result of appropriate neural activity if its minimum duration is 0.5 seconds.”
In this context, it is interesting to note that Joshua Brown and Todd Braver discovered in their experiment a kind of early warning system of the brain that alerts the test subjects unconsciously to wrong decisions. Hence, there is an unconscious “sixth sense” besides the conscious veto. Using fMRI, brain researchers were able to locate this in the anterior cingulate cortex (ACC) of the anterior frontal lobe.
The test subjects had to solve tasks on a computer screen by pressing two alternative keys. In the beginning, the decisions were easy. But then more and more difficult tasks were interspersed. Recorded every two-and-a-half-seconds, the fMRI images indicated that the subjects unconsciously concentrated on the more difficult tasks. In return, they received signals from the ACC that they were not aware of. Brown suspects that the indigenous people of the Pacific region, who saved themselves from the devastating tsunami on 26 December 2004 by visiting higher places even before the fatal tsunami hit, had been warned in this way. Many “modern” people, on the other hand, had probably mistrusted their “sixth sense” and paid for it with their lives.
Known for about two decades, the ACC brain region was hitherto primarily regarded as a centre for conflict processing. It was also known that this centre does not work properly in the case of severe psychological disorders, such as obsessive-compulsive neuroses and schizophrenia. Joshua Brown pointed out in Washington that the ACC is stimulated by the well-known neurotransmitter dopamine. To what extent this knowledge can be used for the treatment of mental illnesses is yet to be determined.
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