Editor's key points
- Neuroimaging can improve our understanding of pain mechanisms, analgesic action and the placebo effect.
- New modelling approaches can explore the dynamic processes influencing pain perception.
- Neural mechanisms of the effects of personality and expectancy on pain perception and analgesia have been explored.
- Future developments will continue to expand our knowledge of pain mechanisms, allowing translation from laboratory to clinic.
Pain is an unpleasant sensation that is associated with, or described in terms of, a bodily injury.1
Clinicians have long regarded pain as a symptom or warning of disease that should be investigated to expedite treatment of pathology. Unfortunately, medicine does not yet possess every cure, or indeed knowledge of every pathophysiology that can generate pain. Pain can persist despite the best efforts of physicians. Chronic pain is currently defined by the duration of physical symptoms but is, in reality, suffering strongly associated with feelings of anxiety, depression, and despair.2
In the individual, chronic pain is highly influenced by disease pathophysiology, psychological state, and social milieu. The pathogenesis of chronic pain syndromes is often unclear. Research continues to suggest specific patho physiologies that may distinguish between different chronic pain syndromes, for example, fibromyalgia, complex regional pain syndrome. Whether these clinical syndromes can be distinguished as diseases in their own right with specific treatments, or considered as a collection of symptoms that are driven by shared mechanisms, remains unclear. Regardless, psychosocial factors can supervene to influence how pain is perceived or reported by patients, and these factors can operate unconsciously. Their contribution to the chronic pain state further determines appropriate and holistic management of the patient. Hence, there is a desperate need for additional methods that can quantify disease load or psychosocial contributions to the chronic pain state in patients.
In the fifth century BC, Hippocrates declared that pain, like all consciousness, must emerge from brain activity.3
Robust scientific evidence for that philosophical intuition arrived much later (two decades ago) with the demonstration of increased and localized brain activation during pain in humans.4
We now accept that pain may be caused by bodily injury, but as a consciousness, must be generated in the brain.
Functional magnetic resonance imaging (fMRI), positron emission tomography (PET), magnetoencephalography (MEG), and scalp electroencephalography (EEG) are commonly used to study the neural bases of pain. Researchers are also increasingly using other magnetic resonance-based measures (e.g. diffusion tensor imaging, spectroscopy, and volumetric imaging) to assess pain-related changes in the brain's wiring, chemistry, and structure in order to gain further insights into the neurobiology of pain, particularly chronic pain. There are excellent reviews written recently to summarize the findings of neuroimaging studies in healthy individuals and in patients.5,6
Here, we focus on recent neuroimaging studies that continue to shape our understanding of pain in health, disease, and illness. We review the progress in neuroimaging research that is contributing to the development of clinically relevant tools for the management of pain in patients.