Learning processes influence pain perception
In connection with pain memory, the research of the Mannheim scientists around PD Dr. Dieter Kleinböhl and Prof. Dr. med. Rupert Hölzl of importance: In one experiment, the sensitivity to pain of healthy participants in the study could be significantly increased, without them being aware of it. Conversely, sensitivity could be lowered in the same way, depending on the consequences that followed the perception reactions.
For their study sponsored by the German Research Foundation (DFG), the researchers were honored at the German Pain Congress in Berlin with the prize of 3, 500 euros for the category "Basic Research" of the Förderpreis für Schmerzforschung 2006. The experiment went like this: The subjects were given a heat stimulus by a so-called thermode on the hand. They were allowed to regulate the temperature themselves.
Their task: they should keep the perceived stimulus intensity constant. "In healthy volunteers, getting used to just painful stimuli usually sets the temperature higher over time to keep the sensation the same, " Dr. Kleinböhl.
"In chronic pain, as in back pain, on the other hand, there is no habituation to such stimuli - here comes sensibilization, ie an increase in the subjective pain sensation." The question was whether such an altered perception of pain can arise through unconscious learning processes. To find out, the researchers examined healthy people under two conditions. The task of keeping the sensation intensity of the heat stimulus constant remained.
In one group, a sensitization reaction was "boosted" by a subsequent further decrease in temperature. The habituation reactions, however, were "punished" by a subsequent temperature increase.
In the second group it was the other way around: here habituation was intensified and sensitization was punished. It was found that in the group in which the perception of pain was intensified, increased sensitization reactions to heat stimuli occurred, while in the other group more habituation reactions were found. In the group with learned sensitization, it was also shown that with decreasing stimuli, the personal sensation remained the same.
Participants were unaware of this increased sensitivity to pain gradually increasing throughout the course of the experiment.