Pain modulation by self-generated expectations.

Pain perception is an individual and complex process, influenced by biological, social, and psychological factors via top-down modulatory pathways. One factor which plays an important role in pain perception is expectations, which have been popularly examined in placebo and Hyperalgesia studies, showing that pain perception can be modulated by manipulating expectations of treatments, pain stimuli or outcome. This preregistered EEG study provides compelling evidence for the high efficacy of self-generated expectation in modulating pain perception in direct comparison to externally induced expectation in a typical placebo paradigm. 42 participants were asked to generate expectations based on visual cues towards a subsequent pain stimulus and either lighten, enhance, or not actively influence their pain expectation. The behavioural results showed that pain perception was significantly altered by self-generated expectations, and that all three conditions differed significantly from each other regarding the reported pain. Notably, self-regulation produced more pronounced effects than externally induced expectations in direct comparison to the results of a previous placebo interventions using the identical experimental layout, indicating that deception is unnecessary for effective pain modulation. EEG analyses revealed differential neural processing among conditions, particularly within gamma-band activity linked to pain perception, underscoring the influence of self-generated expectations on neural responses. These findings provide evidence that even expectations created on a voluntary basis directly influence pain perception, and that manipulating strategies used in placebo studies such as conditioning, verbal instructions and observational learning may not be necessary to evoke the described effects.