Brain activity associated with painfully hot stimuli applied to the upper limb: a meta-analysis

The capacity of pain to alert against potential injury or focus attention on damaged tissue is enhanced by the intrinsically aversive nature of the experience. Finding methods to relieve pain will ultimately be facilitated by deeper understanding of the processes that contribute to the experience, and functional brain imaging has contributed substantially toward that end. An impressive body of literature has identified a distributed network of pain-related activity in the brain that is subject to considerable modulation by different stimulus parameters, contextual factors, and clinical conditions. The fundamental substrates of the pain network are yet to be distilled from the highly variable results of studies published thus far. Qualitative reviews of the pain-imaging literature have been contributory, but lack the greater surety of quantitative methods. We employ the activation likelihood estimation (ALE) meta-analytic technique to establish the most consistent activations among studies reporting brain responses subsequent to the application of noxious heat. A network of pain-related activity was replicated for stimuli to either upper limb that included two discernible regions of the mid-anterior cingulate cortex, bilateral thalami, insula, and opercula cortices, posterior parietal cortex, premotor cortex, supplementary motor area, and cerebellum. The findings of the meta-analysis resonate with other streams of information that continue to enhance our understanding of pain in the brain. The results also point toward new areas of research that may be fruitful for the exploration of central pain processing.