Primary somatosensory cortex and pain perception: Yes sir, your pain is in your head (Part I)

Abstract

This Focus article proposes that the primary somatosensory cortex (SI) is the first level of conscious pain perception, treating the incoming information about pain as any other novel stimulus. The cortical processes underlying conscious pain perception are distributed in nature and are probably similar to cortical processes underlying conscious perception of other sensory modalities, like touch, hearing, or vision. In general, processes in SI are very dynamic across all somatosensory modalities, and the sensory cortices provide important inputs for motor control and performance. But SI is not the “pain center,” because it is the interaction of SI with the other pain-related cortical and subcortical areas and structures, rather than activity of SI, that results in experience of pain. So destruction of SI leads to altered pain perception and not to abolition of pain. Any discussion regarding pain perception has to address the differences between acute pain and chronic pain, because of their biological difference and because of the varying neural processes underlying each one. The most significant difference is neuroplasticity in chronic pain. Consequently, properties of SI nociceptive neurons are altered in subjects with chronic pain when compared to pain responses of SI neurons in subjects without chronic pain.