Postural correlates of painful stimuli exposure: impact of mental simulation processes and pain-level of the stimuli.

Previous studies have reported (i) freezing-like posturographic correlates in response to painful as compared to non-painful scenes vision (Lelard et al., Front Hum Neurosci 7:4, 2013) and (ii) an increase of this response during the mental simulation as compared to the passive viewing of the painful scenes (Lelard et al., Front Psychol 8:2012, 2017). The main objective of the present study was to explore the modulation of posturographic correlates of painful scenes vision by the level of depicted pain and the influence of mental simulation on this modulation. Thirty-six participants (36.3 ± 11.4 years old) were included in this study. During the experiment, participants had to stand on a posturographic platform. Three types of static visual stimuli were randomly depicting different pain-level situations: no-pain, low-pain, high-pain. In a first run, participants watched these stimuli passively (passive condition); in a second run, they were asked to "imagine that they were personally experiencing the situations they were about to see" (mental simulation condition). For each picture, subjective ratings were recorded for displeasure and desire to avoid at the end of the posturographic session. Results support an approach-type behavior in response to high-pain stimuli in the passive condition which becomes a withdrawal-type behavior in the mental simulation condition. Moreover, this withdrawal-type behavior is modulated by the level of depicted pain and this modulation does not appear for the subjective data. As a conclusion, these results are in accordance with those of previous studies showing the modulation of posturographic correlates of pain perception by mental simulation and report, for the first time, modulation of this effect by the level of depicted pain. The dichotomy of this modulatory effect between subjective and objective data is discussed as well as the finding of an approach-type behavior towards painful stimuli when passively viewing them becoming a withdrawal-type behavior when mental simulation is applied to the same stimuli.