Modern pharmacology provides us with several effective analgesia methods (e.g. pills, injections, creams). Despite working well for acute pain, they are ineffective for chronic pain, a major problem affecting approx. 20% of the EU population. Chronic pain can persist for months or even years and is associated with an over-sensitive and over-responsive nervous system. In contrast to acute pain, it is not caused by physical damage to the body and is believed to result from a complex interplay of biological, psychological and social factors, where conditioned pain-related fear is partially responsible for the symptom's chronicity maintenance and perpetuation. For this reason, even strong opioids are usually helpless but often overprescribed. Their abuse is a serious health problem which can even lead to death through overdose.
As a result, it is crucial to investigate other analgesia methods not based on active substances. Their effectiveness depends on many factors, e.g. earlier positive/negative experiences or our attitude and expectations related to their effectiveness. Such relationships are acquired via a learning mechanism called classical conditioning (CC). In CC a previously neutral stimulus (the conditioned stimulus, CS) is paired with a biologically potent stimulus (the unconditioned stimulus, US) and starts to elicit a conditioned reaction (CR) that is similar to the one elicited by the US. Our cognition modulates pain perception and placebo analgesia, which works through the expectation of pain decrease induced via CC, is the best example of it.
Concluding, laboratory studies where placebo manipulation is introduced during fear conditioning may help to recognise the specific role of expectations that modulate pain perception. Moreover, investigating fear conditioning processes can be important to explain and find markers that may help in the early recognition of potential pain problems. Specifically, examining how the sensory response system adapts to relevant or irrelevant information and recognising the abnormalities in this process provides a promising method of prediction of further disabilities. Such investigation has great potential in clinical practice since it can help develop adequate pain therapy and pain management strategy. Consequently, the main objectives of this project were to understand the mechanisms of information prioritization, how neutral stimuli gain their relevance in the process of learning (fear conditioning) and to investigate if placebo manipulation (consciously or unconsciously formed expectations) influences different aspects of experience (e.g. during anticipation of pain/mid-pain/tactile/no-stimuli delivery, administration of stimulus and post-stimulus pain ratings).
