Pain affect encoded in human anterior cingulate but not somatosensory cortex

Area of Science:

• Neuroscience
• Pain Research
• Cognitive Neuroscience

Background:

• Multiple human cerebral cortex regions activate during pain perception.
• The specific roles of these cortical areas in the pain experience remain unclear.
• Differentiating sensory intensity from emotional affect in pain processing is crucial.

Purpose of the Study:

• To distinguish cortical areas associated with the emotional component (affect) of pain.
• To investigate the neural basis of pain affect by manipulating subjective unpleasantness.
• To test the hypothesis linking frontal-lobe limbic activity to pain affect.

Main Methods:

• Utilized hypnotic suggestions to selectively alter the unpleasantness of noxious stimuli.
• Maintained perceived pain intensity constant while modifying the affective quality.
• Employed positron emission tomography (PET) to measure pain-evoked brain activity.

Main Results:

• Positron emission tomography revealed significant changes in pain-evoked activity within the anterior cingulate cortex.
• Anterior cingulate cortex activity changes correlated with the altered perception of pain unpleasantness.
• Activation in the primary somatosensory cortex remained unchanged, indicating its role is not primarily in pain affect.

Conclusions:

• Provides direct experimental evidence in humans linking frontal-lobe limbic activity, specifically the anterior cingulate cortex, with pain affect.
• Supports the hypothesis that the anterior cingulate cortex encodes the perceived unpleasantness of pain.
• Findings align with and extend early clinical lesion studies on the neural basis of pain affect.