Abstract
Background: Emotional context may play a crucial role in movement production. According to simulation theories, emotional states affect motor systems. The aim of this study was to compare postural responses assessed by posturography and electromyography when subjects were instructed to imagine themselves in a painful or a non-painful situation.Methods: Twenty-nine subjects (22.3 ± 3.7 years) participated in this study. While standing quietly on a posturographic platform, they were instructed to imagine themselves in a painful or non-painful situation. Displacement of the center of pressure (COP), leg muscle electromyographic activity, heart rate, and electrodermal activity were assessed in response to painful and non-painful situations.Results: The anteroposterior path was shorter (p < 0.05) when subjects imagined themselves in a painful situation (M = 148.0 ± 33.4 mm) compared to a non-painful situation (158.2 ± 38.7 mm). Higher tibialis anterior (TA) activity (RMS-TA = 3.38 ± 1.95% vs. 3.24 ± 1.85%; p < 0.001) and higher variability of soleus (SO) activity (variation coefficient of RMS-SO = 13.5 ± 16.2% vs. M = 9.0 ± 7.2%; p < 0.05) were also observed in painful compared to non-painful situations. No significant changes were observed for other physiological data.Conclusion: This study demonstrates that simulation of painful situations induces changes in postural control and leg muscle activation compared to non-painful situations, as increased stiffness was demonstrated in response to aversive pictures in accordance with previous results.
Highlights
The interrelation between the motor and affective components of behavior has been studied for a long time
Higher tibialis anterior (TA) activity (RMS-TA = 3.38 ± 1.95% vs. 3.24 ± 1.85%; p < 0.001) and higher variability of soleus (SO) activity were observed in painful compared to non-painful situations
This study demonstrates that simulation of painful situations induces changes in postural control and leg muscle activation compared to non-painful situations, as increased stiffness was demonstrated in response to aversive pictures in accordance with previous results
Summary
The interrelation between the motor and affective components of behavior has been studied for a long time. As noted by Popper (1968), “Plato’s structure of the soul is characterized by an unstable equilibrium— a schism—between its upper functions, the instincts or appetites.”. As part of this history, Charles Darwin made a major contribution by arguing that an emotion induces adaptation of behavioral responses according to the environmental context that triggered this emotion (Darwin, 1872). Several authors have tried to explain behavior by means of a biphasic model in which emotional stimuli should be considered as appetitive or defensive (Lang et al, 2008) and might result in approach-withdrawal responses. The aim of this study was to compare postural responses assessed by posturography and electromyography when subjects were instructed to imagine themselves in a painful or a non-painful situation
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