Cortical thickness correlates of pain and temperature sensitivity

It is well established that there is individual variability in pain and temperature sensitivity. Functional brain imaging studies have found that interindividual heat pain variability correlates with brain activity in sensory and pain modulation areas. Thus, it is possible that these individual differences are associated with variability in gray matter thickness of cortical regions involved in thermoreception and pain. To test this, we investigated the relationship between thermal thresholds and cortical thickness in 80 healthy subjects. Subjects underwent a psychophysical session to determine their cool detection (CD), warm detection (WD), cold pain (CP), and heat pain (HP) threshold. A high-resolution structural magnetic resonance imaging scan was acquired for each subject. We correlated each threshold measure to cortical thickness of regions associated with thermoreception and pain. The mean (± SD) thresholds were 30.7°C (± 0.8) for CD, 33.8°C (± 0.7) for WD, 11.7°C (± 9.7) for CP, and 45.3°C (± 2.8) for HP. The brain gray matter analysis revealed a strong correlation between greater thermal and pain sensitivity and cortical thickening of the primary somatosensory cortex. Additionally, greater sensitivity to cool stimuli correlated with cortical thickening in the paracentral lobule, and greater WD correlated with cortical thinning in the anterior midcingulate cortex. We also found that greater HP sensitivity correlated with thickening in the posterior midcingulate cortex and the orbitofrontal cortex. These cortical gray matter correlates of thermal and pain sensitivity provide a neural basis for individual differences in thermal sensitivity.