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Cortical Responses to Thermal Pain Depend on Stimulus Size: A Functional MRI Study
1 Department of Neurosurgery and 2 Department of Radiology, State University of New York Upstate Medical University, Syracuse, New York 13210 Apkarian, A. Vania, Patricia A. Gelnar, Beth R. Krauss, and Nikolaus M. Szeverenyi. Cortical Responses to Thermal Pain Depend on Stimulus Size: A Function...
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Published in: | Journal of neurophysiology 2000-05, Vol.83 (5), p.3113-3122 |
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Main Authors: | , , , |
Format: | Article |
Language: | English |
Subjects: | |
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Online Access: | Get full text |
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Summary: | 1 Department of Neurosurgery and
2 Department of Radiology, State University of
New York Upstate Medical University, Syracuse, New York 13210
Apkarian, A. Vania,
Patricia A. Gelnar,
Beth R. Krauss, and
Nikolaus M. Szeverenyi.
Cortical Responses to Thermal Pain Depend on Stimulus Size: A
Functional MRI Study. J. Neurophysiol. 83: 3113-3122, 2000. Cortical activity patterns to thermal
painful stimuli of two different sizes were examined in normal
volunteers using functional magnetic resonance imaging (fMRI). Seven
right-handed subjects were studied when the painful stimulus applied to
the right hand fingers covered either 1,074-mm 2 -area large
stimulator or 21-mm 2 -area small stimulator. Stimulus
temperatures were adjusted to give rise to equivalent moderately
painful ratings. fMRI signal increases and decreases were determined
for the contralateral parietal and motor areas. When the overall
activity in these regions was compared across subjects, increased fMRI
activity was observed over more brain volume with the larger
stimulator, whereas decreased fMRI activity was seen in more brain
volume for the smaller stimulator. The individual subject and
group-averaged activity patterns indicated regional specific
differences in increased and decreased fMRI activity. The small
stimulator resulted in decreased fMRI responses throughout the upper
body representation in both primary somatosensory and motor cortices.
In contrast, no decreased fMRI signals were seen in the secondary
somatosensory cortex and in the insula. In another seven volunteers,
the effects of the size of the thermal painful stimulus on vibrotactile
thresholds were examined psychophysically. Painful stimuli were
delivered to the fingers and vibrotactile thresholds were measured on
the arm just distal to the elbow. Consistent with the fMRI results in
the primary somatosensory cortex, painful thermal stimuli using the
small stimulator increased vibrotactile thresholds on the forearm,
whereas similarly painful stimuli using the large stimulator had no
effect on forearm vibrotactile thresholds. These results are discussed
in relation to the cortical dynamics for pain perception and in
relation to the center-surround organization of cortical neurons. |
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ISSN: | 0022-3077 1522-1598 |
DOI: | 10.1152/jn.2000.83.5.3113 |