http://www.jneurosci.org/content/33/34/13784.abstract
Abstract
Nocebo hyperalgesia is an increase in
subjective pain perception after a patient or subject underwent an inert
treatment without
any active ingredient. For example, verbal
suggestion of increased pain can enhance both pain experience and
responses in
pain-related cortical brain areas. However,
changes in cortical pain responses may be secondary to earlier
amplification of
incoming pain signals within the spinal cord. To
test for a potential early enhancement of pain signals in the dorsal
horn
of the spinal cord, we combined a nocebo heat
pain paradigm with spinal functional magnetic resonance imaging in
healthy volunteers.
We found that local application of an inert
nocebo cream on the forearm increased pain ratings compared with a
control cream,
and also reduced pain thresholds on the
nocebo-treated skin patch. On the neurobiological level, pain
stimulation induced
a strong activation in the spinal cord at the
level of the stimulated dermatomes C5/C6. Comparing pain stimulation
under nocebo
to a control pain stimulation of the same
physical intensity revealed enhanced pain-related activity in the
ipsilateral dorsal
horn of the spinal cord. Importantly, the
activation of the main effect of pain and the nocebo effect spatially
overlapped.
The current study thus provides direct evidence
for a pain-facilitating mechanism in the human spinal cord before
cortical
processing, which can be activated by cognitive
manipulations such as nocebo treatments.
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