6533b7d1fe1ef96bd125d611

RESEARCH PRODUCT

Spinothalamic and thalamocortical nociceptive pathways

subject

description

The concept that the perception of a stimulus as being painful requires activity in parts of the cerebral cortex has gained universal recognition within the past 10 years. 28 The large number of functional imaging studies in humans, appearing during that period, have greatly contributed to this development by showing consistent evidence for activation of various cortical areas by painful stimuli, including the primary and secondary somatosensory cortex, the insula, the anterior cingulate gyrus, and prefrontal cortical areas. Thus, the sense of pain—like all other senses— has a representation within the cerebral cortex. These imaging studies, however, did not reveal the pathways by which a painful stimulus can activate the cerebral cortex. Attempts to trace the nociceptive pathways beyond the thalamus have traditionally been hampered by the pronounced convergence with other pathways within the same thalamic nuclei. This problem and its potential solutions will be discussed in this commentary article. The most elegant solution to the problem of finding nociceptive thalamocortical pathways would be the discovery of a new thalamic nucleus that is specific for processing information from painful stimuli (and maybe projects to some of the cortical areas mentioned above). In a series of papers, Craig and coworkers seem to have provided exactly this solution with the nuclei that they called the posterior part of the ventral medial thalamic nucleus (VMpo) and the ventral caudal part of the medial dorsal nucleus (MDvc). 10 These findings have been enthusiastically received by some authors, including those of several textbook chapters. Other authors with long experience in the field, however, have been unable to replicate some of these findings. The review article by Willis and coworkers provides a critical summary of both the traditional nociceptive pathways through ventrobasal thalamus and the pathways through the newly identified nuclei. 32