Early decay of pain-related cerebral activation in functional magnetic resonance imaging: comparison with visual and motor tasks.
BACKGROUND
Although pain-related activation was localized in multiple brain areas by functional imaging, the temporal profile of its signal has been poorly understood. The authors characterized the temporal evolution of such activation in comparison to that by conventional visual and motor tasks using functional magnetic resonance imaging.


METHODS
Five right-handed volunteers underwent whole brain echo-planar imaging on a 3 T magnetic resonance imaging scanner while they received pain stimulus on the right and left forearm and performed visually guided saccade and finger tapping tasks. Pain stimulus on the right and left forearm consisted of four cycles of 15-s stimulus at 47.2-49.0 degrees C, interleaved with 30-s control at 32 degrees C, delivered by a Peltier-type thermode, and visually guided saccade and finger tapping of three cycles of 30-s active and 30-s rest conditions. Voxel-wise t statistical maps were standardized and averaged across subjects. Blood oxygenation level-dependent signal time courses were analyzed at local maxima of representative activation clusters (t > 3.5).


RESULTS
Pain stimulus on the right forearm activated the secondary somatosensory (S2), superior temporal, anterior cingulate, insular, prefrontal cortices, premotor area, and lenticular nucleus. Pain stimulus on the left forearm activated similar but fewer areas at less signal intensity. The S2 activation was dominant on the contralateral hemisphere. Pain-related activation was statistically weaker and showed less consistent signal time courses than visually guided saccade- and finger tapping-related activation. Pain-related signals decayed earlier before the end of stimulus, in contrast to well-sustained signal plateaus induced by visually guided saccade and finger tapping.


CONCLUSIONS
The authors speculate that pain-related blood oxygenation level-dependent signals were attenuated by the pain-induced global cerebral blood flow decrease or activation of the descending pain inhibitory systems.
Kurata
Jiro
J
Department of Anesthesiology and Critical Care Medicine, University of Pittsburgh, Pennsylvania 15213-2582, USA. kurata@pitt.edu
Thulborn
Keith R
KR
Gyulai
Ferenc E
FE
Firestone
Leonard L
LL
D000328:Adult; D001921:Brain / Q000503:physiopathology*; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D010146:Pain / Q000503:physiopathology*; D012438:Saccades
D010100:Oxygen