Rumination, interoceptive awareness and suggestibility predict the occurrence of the thermal grill illusion

ruminationInterposed non-noxious cold and warm cutaneous stimuli
applied via a thermal grill have repeatedly been shown to
generate a paradoxical pain sensation, also described as
‘thermal grill illusion of pain’.
According to the ‘central disinhibition theory’ proposed by
Craig and Bushnell [1], the pain phenomenon commonly
qualified as burning can be explained by “an unmasking of
cold-evoked activity of polymodal nociceptive lamina I
spinothalamic neurons (activation by polymodal Cnociceptors)
resulting from the reduction of normal coldevoked
activity of thermoreceptive lamina I spinothalamic
neurons (activation by Aδ cooling thermoreceptors) by
spatial summation of the simultaneous warm stimuli in the
thermoreceptive but not the nociceptive neurons.”
Since a significant part of the tested subjects do however
not display the thermal grill percept, it may be
hypothesized that not only physiological-, but also
psychological determinants play a crucial role in the
generation of the paradoxical pain. Sad mood [2] and
anxiety [3] have already been proposed as relevant
psychological factors.
The aim of the present research consisted in validating our
custom made, water-driven and fMRI compatible thermal
grill device [4], in identifying thermal grill ‘responders’
and ‘non-responders’ and in investigating whether different
personality traits or states constitute predictors for the
elicitation of the thermal grill illusion.