Dissociating the neural mechanisms of pain consistency and pain intensity in the trigemino-nociceptive system.
BACKGROUND
Individual differences in pain perception to a standardized nociceptive input are a well-known phenomenon within pain research. Brain structures known to play a crucial role in pain modulatory processes are the rostral/subgenual anterior cingulate cortex (sACC) as well as the periaqueductal gray (PAG), which belong to the endogenous antinociceptive system. However, the exact mechanisms possibly leading to this high level of variance in pain perception are still a matter of debate.


METHODS
Pain perception within the trigemino-vascular system was investigated in 37 healthy volunteers using functional magnetic resonance imaging.


RESULTS
Behavioral results show high levels of variance being inversely correlated to mean pain ratings as well as to an increase in BOLD signal intensity within the sACC. In addition, higher sACC activation was coupled with activation in the PAG the lower the level of intra-individual variance.


CONCLUSIONS
This study gives first indications that coupled BOLD response within brain structures of the antinociceptive system seems to rather not code pain intensity within the trigemino-nociceptive system but the stability of volunteers' pain ratings. Intrinsic mechanisms may modulate the pain perception in the trigemino-vascular system, which is highly involved in headache disorders.
Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Germany.
Inga L
IL
Kröger
Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Germany.
Mareike M
MM
Menz
Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Germany a.may@uke.de.
Arne
A
May
D000328:Adult; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D058748:Pain Perception / Q000502:physiology*; D055815:Young Adult
Variability; fMRI; pain ratings; trigemino-vascular system