[Functional imaging of pain]

Area of Science:

• Neuroscience
• Pain Research
• Functional Neuroimaging

Background:

• Early hypotheses implicated somatosensory cortex (SI), thalamus, and anterior cingulate cortex in pain processing.
• Initial functional imaging studies revealed unexpected bilateral activation in insular and SII cortices during pain conditions.

Purpose of the Study:

• To review the contribution of functional imaging to understanding human nociception.
• To identify key brain regions involved in pain perception and pain relief.

Main Methods:

• Review of functional imaging studies (fMRI, PET) on pain perception.
• Intracerebral recordings and direct electrical brain stimulation to validate imaging findings.
• Analysis of brain activation patterns during pain and pain relief states.

Main Results:

• The operculo-insular cortex consistently shows activation correlating with pain intensity, confirmed by direct stimulation studies.
• Abnormal bilateral recruitment of these areas by innocuous stimuli in neuropathic pain suggests neuroplasticity.
• Medial prefrontal and rostral cingulate areas are associated with pain control, correlating with pain relief magnitude and involving the periaqueductal gray (PAG) and endogenous opioids.

Conclusions:

• The operculo-insular cortex is a primary hub for integrating sensory and intensity aspects of pain.
• Neuroplastic changes in pain-processing areas may underlie conditions like neuropathic pain.
• Distinct brain networks are involved in pain perception versus pain modulation and relief.