ABSTRACT
Since the ascent of functional imaging based on regional cerebral blood flow (rCBF), in particular of functional magnetic resonance imaging (fMRI), many studies have dealt with the processing of pain in the human central nervous system (for review, see Treede et al. 1999). Before the advent of modern cerebral imaging, it has been supposed that the experience of pain is multidimensional (Melzack and Casey 1968). Therefore, it was not surprising that no single central “pain center” has been found. From many functional imaging studies a general notion evolved that pain is processed in a “cerebral pain network.” In a meta-analysis of 69 studies employing experimental pain stimuli, the following cerebral areas were encountered in descending order of frequency: insular cortex (both anterior and posterior), anterior and medial cingulate gyrus, somatosensory thalamus, somatosensory projection fields S2 (operculum) and S1 (gyrus postcentralis), and lateral and medial cortex fields (Apkarian et al. 2005). This “cortical pain network” can roughly be divided in a lateral portion (somatosensory projection areas) supposed to serve mainly the sensory evaluative dimension of pain and a medial portion consisting of limbic and prefrontal areas serving the emotional dimension (Treede et al. 1999).
