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Clinicians knew from experience but finally researchers confirmed that some individuals really are more sensitive to pain than others. Scientists from Wake Forest University Baptist Medical Center published a study this week in the Proceedings of the National Academy of Sciences.
This is the first objective evidence that could confirm that there are individual differences in pain  sensitivity. Using magnetic resonance imaging (MRI) to assess brain function, Coghill and colleagues found that study participants who said that a heat stimulus was intensely painful showed pronounced activation of brain regions that are important in pain. In contrast, people who said that the same stimulus was only mildly painful had only minimal activation of these same areas.
Individuals studied who reported higher levels of pain showed increased activation in the primary somatosensory cortex which contributes to the perception of where a painful stimulus is located on the body and how intense it is and the anterior cingulate cortex, which is involved in the processing the unpleasant feelings evoked by pain. Interestingly, there was very little difference between subjects in activation of the thalamus, which is involved in transmitting pain signals from the spinal cord to higher brain regions.
What this suggests is that incoming painful information is processed by the spinal cord in a generally similar manner. But, once the brain gets involved, the experience becomes very different from one individual to the next. These researchers believes that most individual differences in pain sensitivity are probably 'due to a combination of cognitive factors, such as past experience with pain, emotional state at the time pain is experienced, and expectations about pain.'
Overview of Brain Mechanisms in Pain
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