Background Mental imagery is a powerful method of altering brain activity and
behavioral outcomes, such as performance of cognition and motor skills.
Further, attention and distraction can modulate pain-related neuronal networks
and the perception of pain. This exploratory study examined the effects of
mental imagery-induced attention on pressure pain threshold and cortical
plasticity using transcranial magnetic stimulation (TMS). This blinded,
randomized, and parallel-design trial comprised 30 healthy right-handed male
subjects. Exploratory statistical analyses were performed using ANOVA and
t-tests for pain and TMS assessments. Pearson’s correlation was used to
analyze the association between changes in pain threshold and cortical
excitability. Results In the analysis of pain outcomes, there was no
significant interaction effect on pain between group versus time. In an
exploratory analysis, we only observed a significant effect of group for the
targeted left hand (ANOVA with pain threshold as the dependent variable and
time and group as independent variables). Although there was only a within-
group effect of mental imagery on pain, further analyses showed a significant
positive correlation of changes in pain threshold and cortical excitability
(motor-evoked potentials via TMS). Conclusions Mental imagery has a minor
effect on pain modulation in healthy subjects. Its effects appear to differ
compared with chronic pain, leading to a small decrease in pain threshold.
Assessments of cortical excitability confirmed that these effects are related
to the modulation of pain-related cortical circuits. These exploratory
findings suggest that neuronal plasticity is influenced by pain and that the
mental imagery effects on pain depend on the state of central sensitization