Differentiating Cortical Areas Related to Pain Perception from Stimulus Identification: Temporal Analysis of fMRI Activations in a Painful Thermal Task. A. Vania Apkarian*, Aneela Darbar*, Beth R. Krauss*, Patricia A. Gelnar*, and Nikolaus M. Szeverenyio. Departments of Neurosurgery* and Radiology?, SUNY Health Science Center, Syracuse, New York, 13210.
APStracts 6:0078N, 1999.
In a recent functional magnetic resonance imaging study (fMRI), we reported the cortical areas activated in a thermal painful task and compared the extent of overlap between this cortical network and those activated during a vibrotactile task and a motor task (Gelnar et al. 1999). In the present study we examine the temporal properties of the cortical activations for all three tasks and use linear systems identification techniques to functionally differentiate the cortical regions identified in the painful thermal task. Cortical activity was examined in the contralateral middle third of the brain of 10 right- handed subjects, using echo-planar imaging and a surface coil. In another eight subjects the temporal properties of the thermal task were examined psychophysically. The fMRI impulse response function was estimated from the cortical activations in the vibrotactile and motor tasks and shown to correspond to earlier reports. Given the fMRI impulse response function and the time courses for the thermal stimulus and the associated pain ratings, predictor functions were generated. The correlation between these predictor functions and cortical activations in the painful thermal task indicated a gradual transition of information processing antero-posteriorly in the parietal cortex. Within this region, activity in the anterior areas more closely reflected thermal stimulus parameters, while activity more posteriorly was better related to the temporal properties of pain perception. Insular cortex at the level of the anterior commissure was the region best related to the thermal stimulus, and Brodmann's area 5/7 was the region best related to the pain perception. The functional implications of these observations are discussed. 

Received 24 December 1998; accepted in final form 22 February 1999.
APS Manuscript Number J996-8.
Article publicaton pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1999 The American Physiological Society.
Published in APStracts on 3 March 1999